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Revision as of 22:38, 24 June 2022
You are encouraged to solve this task according to the task description, using any language you may know.
- Task
Show all ways to include text in a language source file that's completely ignored by the compiler or interpreter.
- Related tasks
- See also
11l
<lang 11l>// Single line comment \\ Also single line comment (continuation of the comment in previous line)
\[ This is a multi line comment ]
\{ And this }
\( And this )
\‘ And this ’</lang>
360 Assembly
<lang 360 Assembly>
- An asterisk in column one denotes a comment line
- Comments may also follow any syntactically complete instruction:
LA 1,0 Comment
NOP Comment (after a NOP instruction)
- Comments after instructions with omitted operands require a comma ","
END , Comment (without comma, "Comment" assumed an operand of "END")
</lang>
4D
<lang 4d>`Comments in 4th Dimension begin with the accent character and extend to the end of the line (until 4D version 2004). // This is a comment starting from 4D v11 and newer. Accent character is replaced by //</lang>
6502 Assembly
Note: syntax depends on the assembler software but use of a semicolon is fairly standard <lang 6502 Assembly> nop ; comments begin with a semicolon</lang>
68000 Assembly
Note: syntax depends on the assembler software but use of a semicolon is fairly standard
EASy68k uses * as the comment character. VASM uses a semicolon ; <lang 68000devpac> MOVEM.L D0-D7/A0-A6,-(SP) ;push all registers onto the stack</lang>
8086 Assembly
Note: syntax depends on the assembler software but use of a semicolon is fairly standard <lang asm> MOV AX, 4C00h ; go back to DOS INT 21h ; BIOS interrupt 21 base 16</lang>
AArch64 Assembly
<lang AArch64 Assembly> /* ARM assembly AARCH64 Raspberry PI 3B */ /* comments multi lines
end comments */
// comment end of ligne
</lang>
ACL2
Just like Common Lisp: <lang Lisp>; Single line comment
- | Multi-line
comment |#</lang>
Action!
Action! supports only single line comments which begin with semicolon. <lang Action!>;This is a comment
PROC Main() ;This is a comment as well RETURN</lang>
- Output:
Screenshot from Atari 8-bit computer
ActionScript
- See Java
Ada
<lang ada>-- All Ada comments begin with "--" and extend to the end of the line</lang>
Agena
Agena has single line comments and two styles of multi-line comments. <lang agena># single line comment
- / multi-line comment
- ends with the "/ followed by #" terminator on the next line
/#
/* multi-line comment - C-style
- ends with the "* followed by /" terminator on the next line
- /</lang>
ALGOL 60
A comment in ALGOL 60 takes the place of a single instruction. <lang algol_60> 'COMMENT' this is a first comment; 'COMMENT'
- this is a second comment ******
</lang>
ALGOL 68
With Standard
Comments can be inserted in variety of ways:
| Algol68 as typically published,
includes bold typeface. |
Quote stropping,
like to Wiki markup. |
Case stropping,
7-bit/ascii implementations. |
Res stropping,
detecting reserved words. |
Point stropping,
6-bits/byte implementations. |
| ¢ The original way of adding your 2 cents worth to a program with the "cent" character ¢ | ¢ TEXT ¢ | |||
| co Style i comment co
comment text comment |
'co' text 'co'
'comment' text 'comment' |
CO text CO
COMMENT text COMMENT |
co text co
comment text comment |
.CO TEXT .CO
.COMMENT TEXT .COMMENT |
| # Style ii comment with the hash character # | # TEXT # | |||
Notes:
- The # test # and ¢ text ¢ comment tends to be used for inline comments. And the COMMENT text COMMENT style tends to be used to comment out entire blocks.
- The script algol68.vim can be used to highlight commented blocks while editing source code.
With Extensions
£ This is a hash/pound comment for a UK keyboard £
ALGOL W
Comments in Algol W can appear anywhere whitespace is allowed. A comment starts with the reserved word 'comment' and ends with the next semi-colon. Alternatively a comment can start with a percent sign and end with the next percent sign or semi-colon.
A single word in the form of an identifier following the reserved word 'end' is also a comment.
<lang algolw>begin
comment a comment;
% another comment
;
% and
another
%
end this_word_is_also_a_comment.</lang>
AmigaE
<lang amigae>/* multiline comment are like C ... */ -> this is a end of line comment</lang>
AntLang
<lang AntLang>2 + 2 /This is a comment</lang>
Apex
<lang apex> System.debug ('I will execute'); // This comment is ignored. /*
I am a large comment, completely ignored as well.
- /
</lang>
APL
<lang apl>⍝ This is a comment</lang>
AppleScript
<lang AppleScript> --This is a single line comment
display dialog "ok" --it can go at the end of a line
- Hash style comments are also supported
(* This is a multi line comment*)
(* This is a comment. --comments can be nested
(* Nested block comment *)
- )
</lang>
<lang AppleScript>display dialog "ok" #Starting in version 2.0, end-line comments can begin with a hash</lang>
Arendelle
Arendelle uses C style comments
ARM Assembly
<lang ARM Assembly> /* ARM assembly Raspberry PI comment one line */ /* comment line 1
comment line 2
- /
mov r0,#0 @ this comment on end of line mov r1,#0 // authorized comment
</lang>
Arturo
<lang rebol>; This is a simple single-line comment
a: 10 ; another single-line comment
- Now, this is a
- multi-line comment</lang>
Asymptote
<lang Asymptote>// double slash to newline</lang>
See programming introduction in the Asymptote manual.
When reading data files a comment character in them can be specified as comment="#" etc. See Files in the Asymptote manual.
AutoHotkey
<lang AutoHotkey>Msgbox, comments demo ; end of line comment /* multiline comment1 multiline comment2
- /</lang>
For multi-line comments, the /* and */ must be on their own separate lines. Nothing else can be on the same line.
AutoIt
<lang AutoIt>
- cs
Everything between the cs and and the ce is commented. Commented code is not used by the computer.
- ce
- individual lines after a semicolon are commented.
</lang>
AWK
The hash symbol # start a comment; it ends at the end of line.
<lang awk>BEGIN { # this code does something
# do something
}</lang>
Axe
<lang axe>.This is a single-line comment</lang>
<lang axe>... This is a multi-line comment ...</lang>
<lang axe>...If 0 This is a comment only if the condition evaluates to zero ...</lang>
<lang axe>...!If 1 This is a comment only if the condition evaluates to nonzero ...</lang>
<lang axe>...Else This is a comment only if the previous conditional comment was executed (and vice versa) ...</lang>
Babel
<lang babel> -- This is a line-comment
This is a block-comment It goes until de-dent
dedent: 0x42 -- The comment block above is now closed </lang>
BASIC
The only truly standard method of marking a comment in BASIC is using the REM keyword. This dates back to (at least) the late 1970's, and should work with most BASICs available today:
<lang gwbasic>100 REM Standard BASIC comments begin with "REM" (remark) and extend to the end of the line 110 PRINT "this is code": REM comment after statement</lang>
This may not be well known, but you may include text after the line number of GOTO and GOSUB statements. This is kind of a comment in absence of labels.
100 GOTO 200HERE 110 GOSUB 300THERE 120 GOTO 400THEOTHERPLACE 130 GOTO 500MOM AND POP
Spaces are removed from non-keyword text. BASIC keywords can be used. List outputs spaces around keywords.
Most BASICs also support alternate comment characters, commonly an apostrophe (single quote):
<lang qbasic> 'this is a comment
PRINT "this is code" 'comment after statement</lang>
Characters other than apostrophe are used in some BASICs. For example, DarkBASIC uses a back-tick character (`, a.k.a. grave accent):
`this is a comment PRINT "this is code" `comment after statement 'this is NOT a comment!
In addition to single-line comments, a few BASICs support block comments. FreeBASIC was influenced by the C family's block comment characters:
/' This is a multi line comment. Requires FreeBASIC 0.16 or later. Last line of the comment block. '/ DIM a AS /' Comment in the middle of statement '/ Integer
Applesoft BASIC
Comment by making a REMark using the REM keyword <lang qbasic>REM COMMENT AFTER THE REM KEYWORD</lang> When LISTing the program a space is added after the REM keyword <lang qbasic>0 REMLEAVE THE SPACE OUT AFTER THE REM WHEN TYPING OR PASTING</lang> The remark extends until the end of the line. Only the first THIS IS CODE is printed. <lang qbasic>10 PRINT "THIS IS CODE" : REM : PRINT "THIS IS CODE"</lang> A comment can come after a GOSUB and when the subroutine returns it continues running the statements after the GOSUB comment. <lang qbasic>20 GOSUB 110COMMENT: PRINT "THIS IS CODE"</lang> Anything after a GOTO or RETURN statement is ignored. <lang qbasic>30 GOTO 40"COMMENT: THIS IS A COMMENT</lang> There are other ways to add spacing and comments to code. <lang qbasic>:::::::::::::::::::::::::::::::::::::: 40 REM 50 : 60 REM<ctrl>+J
70 FOR I = 1 to 10 80 ::::PRINT I;MID$("THIS IS A COMMENT",1,0) 90 NEXT</lang> Typing CONTinue after the program ENDs will result in a ?SYNTAX ERROR. <lang qbasic>100 END : THISISACOMMENT</lang> Use the quotation symbol " before the comment so that spaces are included and keywords are ignored. <lang qbasic>110 RETURN : "COMMENT FOR AND AT THE END</lang>
BaCon
BaCon accepts REM (or single quote apostrophe) for line comments.
C-style block comments can be used with /* and */ pairs; these comment blocks may cross line boundaries.
Inside USEC sections, all comment styles accepted by the configured C compiler will also be ignored.
BASIC256
<lang BASIC256>rem this is a comment
- and this is too
print "this is code" #comment after statement</lang>
IS-BASIC
<lang IS-BASIC>100 REM Standard BASIC comments begin with "REM" (remark) and extend to the end of the line 110 PRINT "this is code" ! comment after statement</lang>
True BASIC
<lang qbasic>!this is a comment
PRINT "this is code" !comment after statement</lang>
Yabasic
<lang yabasic>rem Hey, this is a comment
- the hash-sign too (at beginning of line)
// even the double slash ' and the single quote (at beginning of line) print "Not a comment" # This is an error !! print "Not a comment":// But this is again a valid comment print "Not a comment" // even this. print "Not a comment" rem and this !</lang>
Batch File
<lang dos>rem Single-line comment.</lang>
There is another (undocumented) option, using a double-colon ::. However, this has issues with some syntactic constructs and therefore may raise syntax errors.
<lang dos>:: Another option, though undocumented and known
- to fail in some cases. Best avoided.</lang>
Yet another (undocumented) option, using (not delayed) variable expansion as long as it is undefined. This works because undefined variables result to blank line when expanded using %.
<lang dos>% this works as long as you have no variable named exactly like this sentence. %</lang>
Since comment lines are skipped entirely by the parser, multi-line comments aren't possible even with line continuation.
BBC BASIC
<lang bbcbasic> REM This is a comment which is ignored by the compiler
*| This is a comment which is compiled but ignored at run time</lang>
bc
<lang bc>/* This is a comment. */
2 + /* Comment between tokens. */ 3
"This is a string, /* NOT a comment */."
/*
* A comment can have multiple lines. These asterisks in the middle * of the comment are only for style. You must not nest a comment * inside another comment; the first asterisk-slash ends the comment. */</lang>
<lang bc>#!/usr/bin/bc
- This form of comment is an extension, not part of standard bc.
- Your program must not have a #! shebang line
- unless your bc supports this form of comment.
2 + 3 # It can be after a statement.
a = 1 # The newline is not part of the comment. b = 2 # So this line is a different statement.</lang>
Befunge
Like Brainf***, all characters and whitespace which are not commands are ignored. Also, since the code/data-space is two-dimensional, comments can be placed anywhere that will be untouched by the instruction pointer and data access commands. Finally, in Funge-98, the ; instruction immediately skips to the next ; instruction, which allows to isolate comments from code.
<lang befunge>& read a number 2+ add two .@ display result and exit
^- inline comments -^ <-^- other comments</lang>
<lang befunge>&;read a number;2+;add two;.@;display result and exit;
^- inline comments -^ <-^- other comments
- completely isolated comment block for the paranoid;
- (almost - you can still skip into it.) ;
- </lang>
Blast
<lang blast># A hash symbol at the beginning of a line marks the line as a comment </lang>
BQN
<lang bqn># This is a comment</lang>
Bracmat
Bracmat uses curly braces as comment delimiters. Curly braces inside comments must be balanced. Comments are so much ignored when source code is read, that they do not reappear in listings created by the built-in lst$ function, an otherwise very useful function to autoindent your code.
Brainf***
<lang bf>This is a comment</lang>
Most ASCII characters may be used for comments; only the eight characters "+-<>[],." are Brainf*** commands. Extra care must be used when using punctuation, particularly the comma or period. These are I/O operators and are actually commands rather than comments, and are instead compiled into the program if used and may have to be "debugged" and removed if you forget this issue. Another workaround for this issue is to tactically place the comment inside a "[]" loop which can never be entered (The loop will only be encountered when the active memory cell value is 0).
Brat
<lang brat># Single line comment
- Multi
Line Comment *#</lang>
Brlcad
<lang brlcad>
# Comments in mget scripts are prefixed with a hash symbol ls # comments may appear at the end of a line
</lang>
Burlesque
Burlesque does NOT have comments. However, you can comment code by pushing a string and popping it immediately.
<lang burlesque> "I'm sort of a comment"vv </lang>
Since strings are multi-line strings:
<lang burlesque> "I'm a very long comment spanning over several lines"vv </lang>
C
<lang c>/* This is a comment. */ /* So is this
multiline comment. */</lang>
The comment starts at the /*, and ends at the */. A comment may be used between any tokens. It cannot be used inside tokens, that is, given the code <lang c>struct charisma {}; void f(char/* comment */isma) {}</lang> the function takes an argument of type char, named isma, not an unnamed argument of type charisma.
Comments cannot be nested; that is, if you write <lang c>/* some comment /* trying to nest some other comment */ inside */</lang> the comment ends at the first */, and inside */ is again interpreted as source code (almost certainly causing a compile error). Some compilers have the option to allow nested comments, but this is not a standard feature.
Conditional compilation also can be used to make the compiler ignore some text: <lang c>#if 0 While technically not a comment, this is also ignored by the compiler
- endif</lang>
The trick is that 0 is always false, therefore the text between #if 0 and #endif is never compiled. While this should never be used for actual comments, it's an easy way to comment out some code, especially because it doesn't interfere with normal (documentation) comments.
Conditional compile "comments" can be nested: <lang c>#ifdef UNDEFINED This is not compiled.
- if 0
Nor is this.
- endif
And this still is not compiled.
- endif</lang>
Even though the compiler doesn't see #if 0 text, the preprocessor does. Therefore some minimal rules still have to be followed. For example, the following code is not valid: <lang c>#if 0 This isn't valid.
- endif</lang>
That's because the preprocessor will interpret the apostrophe as beginning of a character constant, and will complain because that character constant isn't terminated with another apostrophe.
Note that the problem mentioned above cannot occur if there's valid code between the #if 0 and #endif.
<lang c>// C++ single-line comments were adopted in the C99 standard.</lang>
C#
<lang csharp>//This is a comment. //This is other comment.
/* This is a comment too. */
/* This is a multi-line comment */</lang>
C++
- See also C
Single line C++-style comments <lang cpp>// This is a comment</lang> C++-style comments start with // and reach up to, but not including, the end of line (more exactly, up to the next unescaped newline). While formally, C++-style comments cannot be nested either, in practice they can: <lang cpp>// This is a valid comment // with a "nested" comment</lang> That's because starting with the first // everything in the line is ignored, including the second //. The fact that the newline is not part of the comment is important for multi-line macro definitions. It means that in the code <lang cpp>#define FOO \
(macro text) // comment (no more macro text)</lang>
the line (no more macro text) is not part of the macro definition. Also escaping the line break at the end of the comment with '\' doesn't help, because that would make the third line part of the comment instead. Comments inside macros therefore have to be C-style.
Chapel
<lang chapel>// single line
/* multi line */</lang>
Chef
<lang Chef>Comment Stew.
This is a comment. The other comment is a loop, but you can name it anything (single word only). You can also name ingredients as comments This is pseudocode.
Ingredients. Ingredient list
Method. Methods. SingleWordCommentOne the Ingredient. Methods. SingleWordCommentTwo until SingleWordCommentOned. Methods.</lang>
ChucK
<lang ChucK> <-- Not common // Usual comment </lang>
Clean
Clean comments are similar to C++. <lang clean>Start = /* This is a multi-
line comment */ 17 // This is a single-line comment</lang>
In contrast to C++ comments can be nested. <lang clean>Start = /* This is a comment /* Nested comment */ still a comment */ 17</lang>
Clojure
Anything from a semicolon to the end of a line is a comment.
<lang lisp>;; This is a comment (defn foo []
123) ; also a comment</lang>
The (comment) macro will prevent a form from being evaluated, returning nil no matter what is contained in the comment. However the forms inside the comment form must be properly parseable (parentheses balanced, etc.) or an exception will be thrown.
<lang lisp>(comment (println (foo)) "bar" :baz 123 (System/exit 0)) ;; does nothing, returns nil</lang>
Finally, the #_ reader macro will cause a form to be ignored by the reader. Unlike (comment), this does not return nil; the surrounding code is evaluated as though the ignored form isn't even there.
<lang lisp>(+ 1 (comment "foo") 3) ;; Throws an exception, because it tries to add nil to an integer (+ 1 #_"foo" 3) ;; Returns 4</lang>
COBOL
Fixed format
<lang cobol> * an asterisk in 7th column comments the line out</lang> A D in the 7th column indicates a debugging line which is treated like a comment unless a compiler flag is set. <lang cobol> D DISPLAY "Debug"</lang>
Free format
<lang cobol>*> This comment syntax was defined (with free format code) in COBOL 2002.</lang>
This indicates a debugging line like above, but if it is used in fixed format files, it must be in the 8th column or beyond. Not necessarily. GnuCOBOL also supports D as an indicator in column 7, the >>D format works (more by trickery than spec) if the angle brackets start in column 5, the D ending up in column 7. The >>D debug marker can then be both fixed and free form compatible. <lang cobol>>>D DISPLAY "Debug"</lang>
NOTE statement
This statement causes everything following it up to the next separator period to be treated as a comment. This statement was deleted in COBOL-74. <lang cobol> NOTE this paragraph is
commented out and ignored
.</lang>
REMARKS and other statements
There are quite a few IDENTIFICATION DIVISION obsolete and extension reserved words that will work in GnuCOBOL 2.
<lang COBOL>
IDENTIFICATION DIVISION.
PROGRAM-ID. program.
AUTHOR. Rest of line ignored.
REMARKS. Rest of line ignored.
REMARKS. More remarks.
SECURITY. line ignored.
INSTALLATION. line ignored.
DATE-WRITTEN. same, human readable dates are allowed for instance
DATE-COMPILED. same.
DATE-MODIFIED. this one is handy when auto-stamped by an editor.
</lang> Those lines can occur multiple times each within the IDENTIFICATION DIVISION. There can be many AUTHORs, SECURITY notes, etc. These words are also supported by other COBOL dialects, but may have different rules on order, multiples allowed of if full stop periods are required (or allowed) before the end of line.
CoffeeScript
<lang coffeescript># one line comment
- multi
line comment ###</lang>
ColdFusion
In tags: <lang cfm>As ColdFusion's grammar is based around HTML syntax, commenting is similar to HTML. </lang>
In script: <lang cfm>/* This is a comment */ // This is also a comment</lang>
Common Lisp
Common Lisp provides line comments (;) and block comments (#|...|#).
Block comments can nest (#|...#|...|#...|#), unlike block comments in e.g. C.
In a common convention, header comments are prefaced with four semicolons, top-level (function level) comments use three, comments for sections of code use two, and margin comments use one.
<lang lisp>;;;; This code implements the foo and bar functions
- The foo function calls bar on the first argument and multiplies the result by the second.
- The arguments are two integers
(defun foo (a b)
;; Call bar and multiply
(* (bar a) ; Calling bar
b))
- The bar function simply adds 3 to the argument
(defun bar (n)
(+ n 3))</lang>
However, comments should not be used for inline documentation, as most defining constructs permit a documentation string (which is then available at runtime).
<lang lisp>(defun bar (n)
"Add 3 to the argument." (+ n 3))
(defclass button (widget)
(label action) (:documentation "This is a push-button widget."))</lang>
Component Pascal
<lang oberon2> (* Comments (* can nest *)
and they can span multiple lines. *)
</lang>
Crystal
<lang ruby># currently, Crystal only supports single-line comments
- This is a doc comment. Any line *directly* above (no blank lines) a module, class, or method is considered a doc comment
- Doc comments are used to generate documentation with `crystal docs`
class Foo end</lang>
D
<lang d>void main() {
// A single line comment.
/* This is a simple C-style comment that can't be nested. Comments mostly work similar to C, newlines are irrelevant. */
/+ This is a nestable comment
/+ See?
+/
+/
/// Documentation single line comment.
/** Simple C-style documentation comment. */
/++ Nestable documenttion comment. +/
}</lang>
Dart
<lang dart>// This is a single line comment, which lasts until the end of the line. The Dart linter prefers this one.
/* This is also a valid single line comment. Unlike the first one, this one terminates after one of these -> */
/*
You can use the syntax above to make multi line comments as well. Like this!
- /
/// These are doc comments. You can use dartdoc to generate doc pages for your classes with these. /// /// Formatting [variable] and [function] names like so allows dartdoc to link to the documentation for those entities. </lang>
dc
There is no comment syntax in POSIX dc. The convention is to make a string on the stack and move it to an unused register; a no-op. <lang dc>[Making and discarding a string acts like a comment] sz</lang> GNU dc added the comment syntax of many other scripting languages. <lang dc># remainder of line is a comment</lang>
Delphi
- See also Pascal
In addition to Pascal, Delphi also allows C++ style single line comments: <lang delphi>// single line comment</lang>
Deluge
Comments are only allowed in places such as "on load" scripts. You cannot put them in form or view definitions.
<lang deluge>// single line comment</lang>
Dragon
<lang dragon>// This is a comment </lang>
<lang dragon>/*
This is a multiple line comment. */</lang>
<lang dragon>
showln "Hello " /* This is an inline comment */ "world"
</lang>
DWScript
<lang delphi>(* This is a comment.
It may extend across multiple lines. *)
{ Alternatively curly braces
can be used. }
/* C-style multi-line comments
are supported */
// and single-line C++ style comments too</lang>
Dyalect
<lang dyalect>/* This is a multi-line comment */
//This is a single-line comment</lang>
Dylan
<lang Dylan>// This is a comment
/*
This is a comment that spans multiple lines
- /</lang>
Déjà Vu
<lang dejavu>#this is a comment !print "this is not a comment, obviously" #this is a comment as well</lang>
E
<lang e># This is a regular comment.
? "This is an Updoc comment, which > is an executable example or test case.".split(" ")
- value: ["This", "is", "an", "Updoc", "comment,", "which
- is", "an", "executable", "example", "or", "test", "case."]</lang>
All comments span to the end of the line; there are no paired-delimiter comment syntaxes. “#” begins a comment anywhere outside of quotes; “?” and “>” begin comments only if they are at the beginning of a line (except for whitespace), because those characters are also used for infix operators.
In Updoc, “?” indicates the beginning of a program fragment, “>” the continuation of one, and “#” begins the expected output from its evaluation; “??” indicates special directives.
EasyLang
<lang># This is a comment</lang>
EchoLisp
<lang lisp> 666 ; this is an end-of-line comment
- |
This is a multi-line comment Nesting is not allowed
|#
- The (info <name> [<string>)] function associates a symbol and a comment
- These info strings are saved in permanent memory (local storage)
- Unicode characters may be used, as everywhere in the language
(define mynumber 666) → mynumber (info 'mynumber "👀 Symbols may be commented with an information string 👺") (info 'mynumber) → displays the above inside the 'info' field. </lang>
ECL
Single-line comments must begin with // <lang ECL>// this is a one-line comment </lang>
Block comments must be delimited with /* and */
<lang ECL> /* this is a block comment - the terminator can be on the same line or any succeeding line – everything in between is ignored */</lang>
EDSAC order code
EDSAC programs were handwritten on "programme sheets" designed for the purpose. The programmer, or a computer operator, then copied the "orders" (instructions) to punched tape for input to the machine. Programme sheets had a column for "notes" (comments), but these were not copied to the tape. Modern simulators, however, accept square brackets as comment delimiters. <lang edsac>[This is a comment] [ And so is this ] [But in 1949 they wouldn't have been]</lang>
EGL
- See Java
Eiffel
<lang Eiffel>-- inline comment, continues until new line</lang>
Ela
<lang Ela>//single line comment
/*multiple line comment*/</lang>
Elena
<lang elena>//single line comment
/*multiple line comment*/</lang>
Elixir
Elixir does not have multiple line comments. <lang elixir>
- single line comment
</lang>
Elm
<lang elm> -- a single line comment
{- a multiline comment
{- can be nested -}
-} </lang>
Emacs Lisp
A comment is started by ; and reaches to the end of the line.
<lang lisp>; This is a comment</lang>
There are some coding conventions for ;; align to indentation, ;;; sections, etc,
Another way to add comments is to use strings at places where the result of an expression is ignored, since they simply evaluate to themselves without any effect. Note that strings can be multi-line: <lang lisp>"This is effectively a comment, if used at a place where the result is ignored"</lang> Note that strings at the beginning of function definitions are interpreted as documentation strings for the function (i.e. Emacs will display them if asked for help about the function), e.g. <lang lisp>(defun subtract-second-from-first (x y)
"This function subtracts its second argument from its first argument." (- y x))</lang>
Due to this, it's debatable if the string at that place can be considered as comment.
Erlang
<lang erlang>% Erlang comments begin with "%" and extend to the end of the line.</lang>
ERRE
<lang ERRE> ! Standard ERRE comments begin with ! and extend to the end of the line
PRINT("this is code") ! comment after statement </lang>
Euphoria
Single line comment: <lang Euphoria>-- This is a comment</lang>
Multiline C-style comment:
<lang Euphoria>/*
This is a comment
- /</lang>
F#
F# accepts C++ type line comments and OCaml type block comments <lang fsharp>// this comments to the end of the line (* this comments a region
which can be multi-line *)</lang>
Factor
<lang factor>! Comments starts with "! "
- ! Or with "#! "
! and last until the end of the line
USE: multiline /* The multiline vocabulary implements
C-like multiline comments. */</lang>
Falcon
Falcon supports C-language style single line and block comments. A single line comment begins with two slashes (//) and ends at the end of the line. A block comment begins with a slash followed by an asterisk, and terminates when an asterisk followed by a slash is met (/*...*/). <lang falcon> /* Start comment block
My Life Story */
// set up my bank account total bank_account_total = 1000000 // Wish this was the case </lang>
FALSE
<lang false>{comments are in curly braces}</lang>
Fancy
<lang fancy># Comments starts with "#"
- and last until the end of the line
</lang>
Fermat
<lang fermat>Function Foo(n) =
{Comments within a function are enclosed within curly brackets.}
{You can make multi-line comments
such as this one.}
n:=n^2 + 3n - 222; {Comments can go after a semicolon.}
n:=n+1;
n.
- comments between functions are preceded by semicolons, like this
Function Bar(n) =
2n-1.</lang>
Fish
Since ><> is a funge-like language, all characters not touched by the command pointer or modified by the p and g commands can be comments. Unlike Brainf***, unknown commands are not ignored by the compiler, they just raise an error. <lang Fish>v This is the Fish version of the Integer sequence task >0>:n1+v all comments here
^o" "< still here
And of course here :)</lang>
Forth
Standard Forth includes a number of ways to add comment text. As with everything in Forth, comment characters are actually words that control the compiler. <lang forth>\ The backslash skips everything else on the line ( The left paren skips everything up to the next right paren on the same line)</lang>
Traditionally, the paren comments are used for "stack effect" notation: <lang forth>: myword ( a b -- c ) ...</lang>
This comment means "myword takes two cells on the stack and leaves one". Sometimes, stack effect comment names give clues about the word's function: <lang forth>: add'em ( a b -- a+b ) + ;
- strlen ( addr -- len ) count nip ;</lang>
Some Forth systems implement other commenting words, such as these words from Win32Forth: <lang forth>\s skips all remaining text in the file (( skips until the next double-paren,
stretching across multiple lines ))
comment:
Ignore all text in this section
comment; doc
Another comment block
enddoc /* C-style comment */ (* Pascal-style comment *)</lang>
Fortran
Compiler: ANSI FORTRAN 77 or compatible (like g77 -strict)
The first six columns in Fortran are traditionally reserved for labels and certain special characters. In particular the letter "C" in the first column indicates a comment:
<lang fortran>C This would be some kind of comment C Usually one would avoid columns 2-6 even in a comment.</lang>
Some Fortran compilers have the extension that comments starting with D are treated as non-comments if a special debugging flag is given at the compiler invocation. For example:
<lang fortran>C If compiled in debugging mode, print the current value of I D PRINT *, I</lang>
ISO Fortran 90 or later have an inline comment (!) syntax:
<lang fortran>real :: a = 0.0 ! initialize A to be zero</lang>
In ISO Fortran 90 or later, "C in first column" comments are only allowed in the "fixed" source form familiar to FORTRAN 77 programmers. The "free" source form only has inline comments (!).
ISO Fortran 95 or later has an optional conditional compilation syntax. If present, it can be used (abused?) to (in effect) comment out blocks of code:
<lang fortran>?? if (.false.) then do while (oh_no)
a = bad_news() b = big_mistake() c = gigo()
end do ?? end if</lang>
FreeBASIC
<lang freebasic>' FB 1.05.0 Win64
' This a single line comment
REM This is another way of writing a single line comment
/'
This is a multi-line comment
'/
/'
Multi-line comments /' can also be nested '/ like this
'/</lang>
Frink
<lang frink> // This is a single-line comment /* This is a comment
that spans multiple lines and so on.
- /
</lang>
Futhark
<lang Futhark> -- Single-line comment
-- Multi-line -- comment (yes, just several single-line comments). </lang>
FutureBasic
<lang futurebasic> // Single line comment ' Single line comment rem Single line comment /* Single line comment */
/*
Multiline comment
- /
</lang>
FUZE BASIC
<lang qbasic>//Comment (No space required)
- Comment (Space required)
REM Comment (Space require) PRINT "This is an inline comment."//Comment (No space required) END</lang>
Gambas
In gambas, comments can be inserted by prefixing them with an apostrophe. The gambas interpreter will ignore the apostrophe and any other characters that follow it until the end of the line:
<lang gambas>
' This whole line is a comment and is ignored by the gambas interpreter print "Hello" ' Comments after an apostrophe are ignored A bold-style comment ' TODO: To Do comment will appear in Task Bar ' FIXME: Fix Me comment will appear in Task Bar ' NOTE: Note commnet will appear in Task Bar
</lang>
GAP
<lang gap># Comment (till end of line)</lang>
gecho
<lang gecho>( this is a test comment... o.O ) 1 2 + .</lang>
Gema
<lang gama>! comment starts with "!" and continues to end of line</lang> A shebang (#!) may be used as a comment in the first line of a file.
Genie
Genie allows comments in code in two different ways. <lang genie>// Comment continues until end of line
/* Comment lasts between delimiters */</lang>
Delimited comments cannot be nested.
GML
single-line comment: <lang GML> // comment starts with "//" and continues to the end of the line</lang>
multi-line comment: <lang GML> /* a multi-line comment starts with slash-asterisk and, ends with asterisk-slash. also note:
* A multi-line comment is ignored inside a string * A multi-line comment can be ended inside a line
- /</lang>
gnuplot
<lang gnuplot># this is a comment
- backslash continues \
a comment to the next \ line or lines</lang>
The way backslash continues a comment means that comments can't usefully be put within a multi-line function definition,
<lang gnuplot># this doesn't work foo(n) = (n \
+ 2 # no good \
+ 3)
- behaves as if you wrote merely
foo(n) = (n+2</lang>
Go
<lang go>// this is a single line comment /* this is
a multi-line block comment.
/* It does not nest */</lang>
Golfscript
<lang golfscript># end of line comment</lang>
Gri
# through to newline.
<lang Gri># this is a comment show 123 # this too is a comment</lang>
// works similarly but is reckoned the "old way" (as of Gri 2.12.23)
<lang>// this is a comment show 123 // this too is a comment</lang>
Both forms can be used in input data files too.
Groovy
- See Java
GW-BASIC
<lang gwbasic>100 REM Standard BASIC comments begin with "REM" (remark) and extend to the end of the line 110 PRINT "this is code": REM comment after statement</lang>
Haskell
<lang haskell>i code = True -- I am a comment.
{- I am also
a comment. {-comments can be nested-}
let u x = x x (this code not compiled)
Are you? -}
-- |This is a Haddock documentation comment for the following code i code = True -- ^This is a Haddock documentation comment for the preceding code
{-|
This is a Haddock documentation block comment
-} i code = True</lang>
Haxe
<lang haxe>// Single line commment.
/*
Multiple line comment.
- /</lang>
HicEst
<lang hicest>! a comment starts with a "!" and ends at the end of the line</lang>
Hope
<lang hope>! All Hope comments begin with "!" and extend to the end of the line</lang>
HTML
<lang html5></lang>
Icon and Unicon
Any text after "#" is a comment. <lang Icon># This is a comment
procedure x(y,z) #: This is a comment and an IPL meta-comment for a procedure </lang> The The Icon Programming Library established conventions for commenting library additions and functions. This included both header block comments and meta comments on procedures within library files.
IDL
The comment character in IDL is the semicolon - everything starting with it and to the end of the line is a comment. Like this:
<lang idl>; The following computes the factorial of a number "n" fact = product(indgen( n )+1) ; where n should be an integer</lang>
Inform 7
<lang inform7>[This is a single-line comment.]
[This is a multi-line comment.]
[Comments can [be nested].]</lang>
Intercal
<lang intercal>PLEASE NOTE This is a comment</lang>
Io
<lang io># Single-line comment
// Single-line comment
/* Multi-line
comment */</lang>
Isabelle
<lang Isabelle>theory Text imports Main begin
(* Top-level Isar comment. *)
end</lang>
J
<lang j>NB. Text that follows 'NB.' has no effect on execution.
0 : 0 Multi-line comments may be placed in strings, like this. )
Note 'example' Another way to record multi-line comments as text is to use 'Note', which is actually a simple program that makes it clearer when defined text is used only to provide comment. )
'A simple string which is not used is legal, and will be discarded'</lang>
Java
Java has two ways to enter normal comments, plus a third type of comment that doubles as a way to generate HTML documentation.
C Style
<lang java>/* This is a comment */</lang>
<lang java>/*
* This is * a multiple * line comment. */</lang>
This C-style comment starts with /* and ends with */. The two delimiters may be on the same or separate lines. This style comment may be used anywhere white space is permitted.
C++ Style (inline)
<lang java>// This is a comment</lang> This C++-style comment starts with // and extends to the end of line.
Java Documentation (Javadoc)
<lang java>/** This is a Javadoc comment */</lang>
<lang java>/**
* This is * a multiple * line Javadoc comment */</lang>
Javadoc is a standardized documentation code for Java. Its comments begin with a forward slash and two stars. Javadoc comments have different tags that signify different things in the methods and classes that they precede.
Sneaky
Your editor will probably colour this as great big comment, but it compiles and prints "Hello World!". Once you've figured out how this works, try this discussion on why it's allowed. <lang java>public class JustComments {
/* \u002A\u002F\u0070\u0075\u0062\u006C\u0069\u0063\u0020\u0073\u0074\u0061\u0074\u0069\u0063 \u0020\u0076\u006F\u0069\u0064\u0020\u006D\u0061\u0069\u006E\u0028 \u0053\u0074\u0072\u0069\u006E\u0067\u005B\u005D\u0061\u0072\u0067\u0073\u0029 \u007B\u0053\u0079\u0073\u0074\u0065\u006D\u002E\u006F\u0075\u0074\u002E \u0070\u0072\u0069\u006E\u0074\u006C\u006E\u0028\u0022\u0048\u0065\u006C\u006C\u006F\u0022 \u002B\u0022\u0020\u0057\u006F\u0072\u006C\u0064\u0021\u0022\u0029\u003B\u007D\u002F\u002A */
}</lang>
JavaScript
<lang javascript>n = n + 1; // This is a comment</lang> <lang javascript>// This is a valid comment // with a "nested" comment</lang> <lang javascript>/* This is a multi line comment // with a "nested" comment and another line in the comment
- /</lang>
JCL
first form <lang JCL> //* This is a comment line (//* in columns 1-3) </lang> second form <lang JCL> /* This is also a comment line (/* in columns 1-3) </lang>
Joy
<lang joy># this is a single line comment
(* this is a multi-line comment *)</lang>
Multi-line comments cannot be nested.
jq
Except when a hash symbol (#) appears within a string, it begins a comment that continues to the end of the line: <lang jq># this is a single line comment "Hello #world" # the first # on this line is part of the jq program </lang>
Jsish
<lang javascript>#!/usr/bin/env/jsish /* Comments, in Jsish */
// to end of line comment, double slash
/*
Enclosed comment, slash star, ending with star slash Cannot be nested, but can cross line boundaries and occur pretty much anywhere whitespace is allowed
- /
var x = 'X'; /* A var called X */ /* active code on this line */ printf("Result %q %d\n", /* comment code mix */ x, /**/42);
- x;
// jsish also handles double slash commented // unit test echo lines as a special case of "expect failure"
- //noname(x);
/*
!EXPECTSTART!
Result X 42 x ==> X noname(x) ==> PASS!: err = can not execute expression: 'noname' not a function
!EXPECTEND!
- /</lang>
- Output:
prompt$ jsish comments.jsi Result X 42 prompt$ jsish --U comments.jsi Result X 42 x ==> X noname(x) ==> PASS!: err = can not execute expression: 'noname' not a function prompt$ jsish -u comments.jsi [PASS] comments.jsi
Julia
<lang Julia># single line
- =
Multi- line comment =#</lang>
K
<lang K> / this is a comment
2+2 / as is this
</lang>
KonsolScript
<lang KonsolScript>//This is a comment. //This is another comment.
/* This is a comment too. */
/* This is a multi-line comment */</lang>
Kotlin
<lang scala>// This is a single line comment
/*
This is a multi-line comment
- /
/*
Multi-line comments
/*
can also be nested
*/
like so
- /
const val CURRENT_VERSION = "1.0.5-2" // A comment can also be added at the end of a line const val /* or even in the middle of a line */ NEXT_MAJOR_VERSION = "1.1"
/**
* This is a documentation comment used by KDoc. * * It's documenting the main function which is the entry-point to a Kotlin executable. * * @param [args] A string array containing the command line arguments (if any) passed to the executable * @return Implicit return value is Unit which signifies no meaningful return value (like 'void' in java) */
fun main(args: Array<String>) {
println("Current stable version is $CURRENT_VERSION")
println("Next major version is $NEXT_MAJOR_VERSION")
}</lang>
Lambdatalk
<lang scheme>
- this is a comment on a single line
°°° this is
a comment
on several lines
°°° </lang>
LabVIEW
This image is a VI Snippet, an executable image of LabVIEW code. The LabVIEW version is shown on the top-right hand corner. You can download it, then drag-and-drop it onto the LabVIEW block diagram from a file browser, and it will appear as runnable, editable code.
Lang5
<lang Lang5># This is a comment.</lang>
langur
Langur has 2 types of comments.
<lang langur># single line comment starts with hash mark
/* inline or multi-line comment uses C-style syntax */ </lang>
As of 0.6.11, comments allow characters designated as "Graphic" by Unicode, Spaces, and Private Use Area code points. Also, certain invisible "spaces," to make it easier to paste in international text (see langurlang.org). The idea around the "allowed" characters is to keep source code from having hidden text or codes and to allay confusion and deception.
Lasso
<lang Lasso >//This is a comment.
/* This is also a comment. */
/* A multi-line comment */
/* ========================== A multi-line comment =========================== */</lang>
LaTeX
In LaTeX, comments look like this: <lang latex>\documentclass{minimal} \begin{document} % This is a comment \end{document}</lang> LaTeX comments start with % and continue up to and including the line break. The fact that the line break itself is commented out as well makes it useful for adding line breaks in the source code of complex macros without LaTeX interpreting them (which may cause extra space or even a paragraph break in the resulting typeset text). For example, the following results in the one word "understandable": <lang latex>\documentclass{minimal} \newcommand{\firstpart}[1]{under#1} \newcommand{\secondpart}{able} \newcommand{\complete}{% \firstpart{stand}% \secondpart} \begin{document} \complete \end{document}</lang> Without the percent sign after \firstpart{stand}, it would have been the two words "understand able".
Liberty BASIC
<lang lb>'This is a comment REM This is a comment
print "This has a comment on the end of the line." 'This is a comment print "This also has a comment on the end of the line." : REM This is a comment</lang>
Lily
There are two kinds of comments:
<lang lily># This is a single-line comment</lang>
and
<lang lily>#[ This is a block comment ]#</lang>
Like with C, block comments don't nest.
Lilypond
<lang lilypond>% This is a comment
%{ This is a comment spanning several lines %}</lang>
Lingo
In Lingo any line starting with "--" is a comment and ignored by the interpreter.
<lang lingo>-- This is a comment. -- This is another comment</lang>
LiveCode
<lang LiveCode>-- comment may appear anywhere on line // comment may appear anywhere on line
- comment may appear anywhere on line
/* this is a block comment that may span any number of lines */</lang>
Logo
<lang logo>; comments come after a semicolon, and last until the end of the line</lang>
Logtalk
<lang logtalk>% single-line comment; extends to the end of the line</lang> <lang logtalk>/* multi-line comment */</lang>
LOLCODE
<lang LOLCODE>OBTW This is a multi line comment TLDR</lang> <lang LOLCODE>BTW This is a single line comment.</lang>
LotusScript
LotusScript has two ways to enter comments. <lang lotusscript>' This is a comment</lang> Wherever the single quote (') is used, the rest of the line is treated as a comment and ignored. Multi-line comments would each need a single quote mark. This style of comment is usually used for making small in-line or single line comments. <lang lotusscript>%REM This is a multi- line comment. %END REM</lang> A %REM marker begins a comment block, and a %END REM marker ends the comment block. This style of comment is used for making longer multi-line comments, often at the beginning of a class, sub or function.
LSE
<lang lse>* Ceci est un commentaire qui prend fin quand la ligne se termine
(* Ceci est un commentaire sur plusieurs lignes comme vous pouvez le voir puisqu'il s'étend sur plusieurs lignes justement... *)
(* Cette exemple est selon la revision LSE-2000 *)</lang>
LSE64
<lang lse64># single line comment (space after # is required)</lang> The author of LSE64 comments the stack effect of words with header comments as follows: <lang lse64># arg1 arg2 yields result|nothing</lang>
Lua
<lang lua>-- A single line comment
--[[A multi-line
comment --]]</lang>
<lang lua>--[====[ A multi-line comment that can contain many square brackets ]====]</lang>
M2000 Interpreter
There is no multi line comment. We have to use ' or \
There are three types of remarks. After statement with a dark color, in a line, with no statements, with the current pen color, and the Rem statement. Rem statement skip statements in current line, but m2000 editor render these using syntax highlight.
<lang M2000 Interpreter> Module Comments {
Print "ok" ' comment at the end of line
Print "ok" \ comment at the end of line
\ comment in one line - different color with previous two
'comment in one line
Rem : Print "ok" ' statements after Rem skipped, but stay with syntax highlight
} Comments
</lang>
M4
<lang M4>eval(2*3) # eval(2*3) "#" and text after it aren't processed but passed along
dnl this text completely disappears, including the new line
divert(-1) Everything diverted to -1 is processed but the output is discarded. A comment could take this form as long as no macro names are used. divert</lang>
- Output:
6 # eval(2*3) "#" and text after it aren't processed but passed along
dnl must be a separate word.
An empty pair of quotes
can separate it from preceding text if necessary
<lang m4>some text`'dnl then a deleted comment</lang>
changecom() can set a different character for #,
<lang m4>changecom(%) % now percent prevents macro expansion</lang>
In GNU m4 an empty changecom() string means no such commenting char at all (but in BSD m4 means reset to the default #)
<lang m4>changecom() GNU m4 now no macro expansion suppression character at all</lang>
In GNU m4 changecom() also takes separate start and end strings and they can be multi-character sequences, allowing for example C style,
<lang m4>changecom(/*,*/) /* GNU m4 now no macro expansion in C style comments */</lang>
Maple
<lang Maple>x := 4: x; # Everything on this line, after this, is a comment.
17; (* This
is a multiline comment *) 23.4;</lang>
- Output:
4
17
23.4
Mathematica / Wolfram Language
<lang Mathematica>(*this is a comment*)</lang> It can be used everywhere and nested if necessary: <lang Mathematica>If[a(*number 1*)<(* is smaller than number 2*) b, True (*return value (*bool true*)*), False (*return bool false*)]</lang> evaluates to: <lang Mathematica>If[a < b, True, False]</lang>
MATLAB
<lang MATLAB>%This is a comment %% Two percent signs and a space are called a cell divider</lang>
Maxima
<lang maxima>/* Comment
/* Nested comment */
- /</lang>
MAXScript
<lang maxscript>-- Two dashes precede a single line comment
/* This is a
multi-line comment */</lang>
MBS
<lang mbs>! A pling in a line starts a comment
INT n:=5 ! Comments can appear at the end of a line
/* A comment block can also be defined using climbstar and starclimb symbols.
This allows comments to be stretched across several lines */</lang>
Metafont
<lang metafont>% this is "to-end-of-line" comment</lang>
Microsoft Small Basic
Microsoft Small Basic uses the quote symbol to mark it's comments. After placing a quote everything in that line will be ignored.
<lang smallbasic>' This is a comment i = i + 1 ' You can also append comments to statements</lang>
min
<lang min>; this is a comment 1 1 + ; add one and one together</lang>
Mirah
<lang mirah>puts 'code' # I am a comment /* This is
* a multiple * line comment */
</lang>
mIRC Scripting Language
<lang mirc>;Single Line Comment /* Multiple Line Comment
- /</lang>
Modula-2
<lang Modula-2>(* Comments (* can nest *)
and they can span multiple lines. *)</lang>
Modula-3
<lang modula3>(* Comments (* can nest *)
and they can span multiple lines. *)</lang>
Monte
<lang Monte>
- This comment goes to the end of the line
/** This comment is multi-line.
Yes, it starts with a two stars and ends with only one. These should only be used for docstrings. */
</lang>
MontiLang
<lang MontiLang> /# This is a comment #/ /# comments can span multiple lines nested comments are not supported #/ </lang>
MOO
<lang moo>"String literals are technically the only long-term comment format"; // Some compilers will, however, compile // one-liners to string literals as well (and vice-versa) /* Classical C-style comments are removed entirely during compile */</lang>
Nanoquery
Comments in Nanoquery must be on a single line. <lang Nanoquery>// this is a comment // this is also a comment</lang>
NATURAL
<lang NATURAL>* This is a comment and extends to the end of the line </lang>
Neko
<lang ActionScript>// Single line comment, of course!
/* Multi line comment!
- /
/** Documentation block <doc>can include XML parsed nodes between doc tags</doc>
- /</lang>
Nemerle
<lang Nemerle>// This comment goes up to the end of the line /* This is a multiline comment */</lang>
NESL
<lang nesl>% This is a comment. %</lang>
NetRexx
NetRexx supports block-comments and line comments. Block comments are started with a /* and terminated with a */. Line comments follow a -- sequence anywhere on a line.
NetRexx supports nested comments (see REXX).
<lang NetRexx>/*
NetRexx comment block
- /
-- NetRexx line comment
</lang>
NewLISP
A comment is started by ; and reaches to the end of the line.
<lang lisp>; This is a comment</lang>
Nim
<lang Python># Nim supports single-line comments
var x = 0 ## Documentation comments start with double hash characters.
var y = 0 ## Documentation comments are a proper part of the syntax (they're not discarded by parser, and a real part of AST).
- [
There are also multi-line comments Everything inside of #[]# is commented. ]#
- You can also discard multiline statements:
discard """This can be considered as a "comment" too This is multi-line""" </lang>
Nix
<lang nix># This comment goes up to the end of the line /* This is a multiline comment */</lang>
NSIS
<lang nsis>
- This is a comment that goes from the # to the end of the line.
- This is a comment that goes from the ; to the end of the
/* This is a multi-line comment */ </lang>
Oberon-2
<lang oberon2> (* this is a comment *) (*
and this is a multiline comment (* with a nested comment *)
- )
</lang>
Objeck
<lang objeck>
- This is a comment.
- This is other comment.
- ~ This is a comment too. ~#
- ~ This is a
multi-line comment ~# </lang>
Objective-C
- See C
OCaml
<lang ocaml>(* This a comment
(* containing nested comment *) *)
(** This an OCamldoc documentation comment *)</lang>
Octave
<lang octave># I am a comment till the end of line % I am a comment till the end of line
%{
This comment spans multiple lines
%} </lang>
Oforth
Oforth has only single line comment (inside or outside definition)
<lang Oforth>// This is a comment...</lang>
ooRexx
Comments in ooRexx follow the same rules as REXX and NetRexx
<lang ooRexx>/*
Multi-line comment block */
-- this type of comment works in ooRexx, NetRexx and some of the more popular REXX implementations like Regina
hour = 0 -- which is, like midnight, dude.
hour = 12 /* time for lunch! works as well (and really everywhere) */
</lang>
Openscad
The openscad geometry compiler supports C++ style comments: <lang openscad> // This is a single line comment
/*
This comment spans multiple lines
- /
</lang>
OxygenBasic
<lang oxygenbasic> ' Basic line comment
- Assembly code line comment
// C line comment /* C block comment */ </lang>
Oz
<lang oz>% one line comment
%% often with double "%" because then the indentation is correct in Emacs
/* multi line
comment
- /
</lang>
PARI/GP
Comments are similar to C. The block comment is identical: /* comment */. The line comment uses backslashes instead of slashes: \\ comment.
Pascal
<lang pascal>(* This is a comment.
It may extend across multiple lines. *)
{ Alternatively curly braces
can be used. }
(* This is a valid comment in Standard Pascal,
but not valid in Turbo Pascal. }
{ The same is true in this case *)</lang>
In Pascal, comments cannot be nested.
PASM
<lang pasm># This is a comment print "Hello\n" # This is also a comment end</lang>
Peloton
Peloton encloses all comments inside <@ OMT></@> (fixed length opcode) or <# OMIT></#> (variable length opcode) whether single- or multi- line. <lang html> <@ OMT>This is a multiline comment</@> </lang> OMT suppresses evaluation of everything contained. There are a variety of extra opcodes which can be used to control how OMT functions at run time.
Perl
Single line comment
<lang perl># this is commented</lang>
These may also be at the end of a line
<lang perl>my $var = 1; # this is the comment part</lang>
Multi-line comments for inline documentation (Plain Old Documentation, or POD in Perl parlance) follow the format:
<lang perl>=pod
Here are my comments this is multi-line
=cut</lang>
Note that technically, both of the lines beginning with the equals sign must be surrounded on either side for compatibility with all "POD" parsers.
Note also that any string beginning with an equals sign, and that appears in the initial column of a line, begins a multi-line comment. It does not have to be a POD "command:" the following are all valid:
<lang perl>=head1 =head4 =over 4 =Any Old String</lang>
Such blocks always end in =cut.
For more info, type at a command prompt (or into a search engine): "perldoc perlpod"
Phix
Single line comment:
-- This is a comment
Nestable multiline comments:
/* This is a comment procedure oldproc() /* This is also a comment */ puts(1,"kill me now") end procedure */ puts(1,"this is not a comment")
- Output:
this is not a comment
PHP
Single line comment:
<lang php># this is commented // this is commented</lang>
These may also be at the end of a line:
<lang php>$var = 1; # this is the comment part $var = 1; // this is the comment part</lang>
Basic syntax for multi-line comments:
<lang php>/* Here are my comments this is multi-line
- /</lang>
Note that; it is more common to see phpDocumentor styled multi-lined comments:
<lang php>/**
* phpdoc Comments * @todo this is a todo stub */</lang>
Picat
<lang Picat> /*
* Multi-line comment */
% Single-line Prolog-style comment </lang>
PicoLisp
<lang PicoLisp># The rest of the line is ignored
- {
This is a multiline comment
}# NIL Immediately stop reading this file. Because all text in the input file following a top-level 'NIL' is ignored.
This is typically used conditionally, with a read-macro expression like `*Dbg so that this text is only read if in debugging mode.</lang>
Pike
<lang pike>// This is a comment. /* This is a
multi line comment */
int e = 3; // end-of-statement comment.</lang>
PL/I
<lang pli>/* This is a comment. */</lang> <lang pli>/* This is a multiline comment.
- /</lang>
Note: In PL/I, comments cannot be nested.
PL/SQL
Single line comment:
<lang plsql>--this is a single line comment</lang>
Multiline comment:
<lang plsql>/* this is a multiline comment
- /</lang>
End of line comment:
<lang plsql>v_var number; --this is an end of line comment</lang>
Plain English
<lang plainenglish>\A comment like this lasts until the end of the line Put 1 plus [there are inline comments too] 1 into a number.</lang>
Plain TeX
The default raw/bare TeX assigns the category code 14 (comment character) to the character %, and plainTeX, as also LaTeX (see here Comments in LaTeX, does not change it; so the % starts a to-end-of-line comment in many TeX macro packages.
<lang tex>% this is a comment This is not.</lang>
The final newline character is eaten and since it normally behaves like a space, the comment can be used to hide the newline:
<lang tex>\def\firstpart#1{under#1} \def\secondpart{able} \def\complete{\firstpart{stand}% \secondpart}
\complete</lang>
Outputs understandable; without % it would output understand able.
Pop11
Pop11 has two kinds of comments: endline and C-like. Endline comment begins with tree consecutive semicolons and ends at the end of line:
<lang pop11>;;; This is a comment</lang>
C-like comments may be multiline:
<lang pop11>/* First line
Second line */</lang>
C-like comments (unlike C) may be nested:
<lang pop11>/* This is a comment /* containing nested comment */ */</lang>
One can also use conditional compilation to comment out sections of code
<lang pop11>#_IF false some code
- _ENDIF</lang>
however, commented out part must consist of valid Pop11 tokens. In particular, C-like comments must balance and strings must be terminated. The following is an error:
<lang pop11>#_IF false This w'ont work
- _ENDIF</lang>
because apostrophe starts an unterminated string.
PostScript
<lang> %This is a legal comment in PostScript </lang>
PowerShell
<lang powershell># single-line comment</lang>
<lang powershell><# multi-line
comment #></lang>
Processing
<lang java>// a single-line comment
/* a multi-line
comment
- /
/*
* a multi-line comment * with some decorative stars */
// comment out a code line // println("foo");
// comment at the end of a line println("foo bar"); // "baz"</lang>
Processing Python mode
<lang python># a single-line comment
""" Not strictly a comment, bare multi-line strings are used in Python as multi-line comments. They are also used as documentation strings or 'docstrings' when placed as the first element inside function or class definitions. """
- comment out a code line
- println("foo")
- comment at the end of a line
println("foo bar") # "baz"
- there is no way to make an inline comment</lang>
ProDOS
I don't know why this is even a task because it should be included in any decent programming language. <lang ProDOS>IGNORELINE your text here</lang>
Prolog
<lang prolog>% this is a single-line comment that extends to the end of the line</lang> <lang prolog>/* This is a multi-line comment */</lang>
PureBasic
PureBasic uses the ";" symbol to mark its comments. All text entered after ";" on a line is ignored by the compiler. <lang PureBasic>;comments come after an unquoted semicolon and last until the end of the line foo = 5 ;This is a comment c$ = ";This is not a comment" ;This is also a comment</lang>
Python
Python uses the "#" symbol to mark it's comments. After placing a "#", everything to the right of it in that line will be ignored.
<lang python># This is a comment foo = 5 # You can also append comments to statements</lang>
Certain 'do nothing' expressions resemble comments
<lang python>"""Un-assigned strings in triple-quotes might be used
as multi-line comments
"""
"triple quoted strings" can be delimited by either 'single' or "double" quote marks; and they can contain mixtures of other quote marks without any need to \escape\ them using any special characters. They also may span multiple lines without special escape characters.
</lang>
Note that strings inserted among program statements in Python are treated as expressions (which, in void context, do nothing). Thus it's possible to "comment out" a section of code by simply wrapping the lines in "triple quotes" (three consecutive instances of quotation marks, or of apostrophes, and terminated with a matching set of the same). Using unassigned strings as comments is frowned on and may also trigger certain linters.
Documentation Strings
Python makes pervasive use of strings which immediately follow class and function definition statements, and those which appear as the first non-blank, non-comment line in any module or program file. These are called "documentation" strings or "docstrings" for short; and they are automatically associated with the __doc__ attribute of the class, function, or module objects in which they are defined. Thus a fragment of code such as: <lang python>#!/usr/bin/env python
- Example of using doc strings
"""My Doc-string example"""
class Foo:
Some documentation for the Foo class
def __init__(self):
"Foo's initialization method's documentation"
def bar():
"""documentation for the bar function"""
if __name__ == "__main__":
print (__doc__) print (Foo.__doc__) print (Foo.__init__.__doc__) print (bar.__doc__)</lang>
... would print each of the various documentation strings in this example. (In this particular example it would print two copies of the first doc string which because __doc__ in the "current" name space is the same as __main__.__doc__ when our program is running as a script). If some other script were to import this file (under the name "example" perhaps) then "My Doc-string example" would be the value of example.__doc__
Python "docstrings" are used by a number of tools to automatically generate documentation (for most of the Python standard libraries, classes, functions, etc, as well as for user programs which define docstrings). They are also used by tools such as doctest to automatically derive test suites from properly formatted examples of class instantiations, function invocations and other usage samples. The standard pydoc utility can search through Python source trees generating documentation and can function as a local web server allowing a programmer to browse "live" hyperlinked documentation of their project.
(As noted above extraneous strings interspersed throughout a Python source file can be used as comments, though this is rarely done in practice; only those strings which lexically follow the definition of a class, function, module or package are assigned to __doc__ attributes in their respective name spaces).
Quackery
<lang Quackery>
( The word "(" is a compiler directive (a builder,
in Quackery jargon) that causes the compiler to
disregard everything until it encounters a ")"
preceded by whitespace.
If you require more than that, it is trivial to
define new comment builders... )
[ behead carriage = until ] builds #
# Now the word "#" will cause the compiler to
# disregard everything from the "#" to the end of
# the line that it occurs on.
[ drop $ "" ] builds commentary
commentary
The word "commentary" will cause the compiler to
disregard everything that comes after it to the
end of the source string or file.</lang>
QB64
CBTJD: 2020/03/12 <lang qb64>REM This is a remark... ' This is also a remark...
IF a = 0 THEN REM (REM follows syntax rules) IF a = 0 THEN '(apostrophe doesn't follow syntax rules, so use END IF after this) END IF
'Metacommands such as $DYNAMIC and $INCLUDE use the REM (or apostrophe). REM $STATIC 'arrays cannot be resized once dimensioned. REM $DYNAMIC 'enables resizing of array dimensions with REDIM. REM $INCLUDE: 'loads a reference file or library.</lang>
R
<lang rsplus># end of line comment</lang>
Racket
<lang racket>
- this is a to-end-of-line coment
- | balanced comment, #| can be nested |# |#
- (this expression is ignored)
- ; the following expression is commented because of the #; in the beginning
(ignored)
</lang>
Raku
(formerly Perl 6)
Single-line comments
A single-line comment starts with # and extends to the end of the line.
<lang perl6># the answer to everything my $x = 42;</lang>
Multi-line comments
A multi-line comment starts with #` and followed by the commented text enclosed by bracketing characters (e.g., (), [], {}, 「」, etc.).
<lang perl6>#`(
Comments beginning with a backtick and one or more opening bracketing characters are embedded comments. They can span more than one line…
)
my $y = #`{ …or only part of a line. } 3;</lang>
Multi-line comments can also be embedded into code.
<lang perl6>for #`(each element in) my @array {
say #`(or print element) $_ #`(with a newline);
}</lang>
Using more than one bracketing character lets you include an unmatched close bracket, as shown below.
<lang perl6>#`{{
This close curly brace } won't terminate the comment early.
}}</lang>
Pod comments
<lang perl6>=begin comment
Pod is the successor to Perl 5's POD. This is the simplest way to use it for multi-line comments. For more about Pod, see Pod: https://docs.perl6.org/language/pod
=end comment</lang>
Pod also provides declarator blocks which are special comments that attach to some source code and can be extracted as documentation. They are either #| or #= and must be immediately followed by either a space or an opening curly brace. In short, blocks starting with #| are attached to the code after them, and blocks starting with #= are attached to the code before them.
<lang perl6>#| Compute the distance between two points in the plane. sub distance(
Rat \x1, #= First point's abscissa, Rat \y1, #= First point's ordinate, Rat \x2, #= Second point's abscissa, Rat \y2, #= Second point's ordinate,
){
return sqrt((x2 - x1)**2 + (y2 - y1)**2)
}</lang>
Raven
<lang raven> # this is a comment</lang>
REBOL
<lang REBOL>
- This is a line comment.
{ Multi-line strings can
be used as comments if you like }
</lang>
Functions have special commenting options which make them self documenting:
<lang REBOL> plus2: func [
"Adds two to a number." n [number!] "The number to increase."
][
n + 2
] </lang>
If you say "help plus2" at REBOL's REPL, you'll get this help information:
USAGE:
PLUS2 n
DESCRIPTION:
Adds two to a number.
PLUS2 is a function value.
ARGUMENTS:
n -- The number to increase. (Type: number)
Relation
<lang Relation> // This is a valid comment // A space is needed after the double slash </lang>
Retro
<lang Retro>( comments are placed between parentheses. A space must follow the opening parenthesis. )</lang>
REXX
It should be noted that comments in the REXX language support nested comments, so comments aren't totally ignored by the REXX interpreter (and compiler).
REXX comments are scanned and preserved for use by the sourceline BIF. [The sourceline BIF allows the retrieval of any or all lines of source (of the REXX program).]
Also, redundant blanks are removed and processed/shown for various trace options (trace is a REXX statement that may show various interpretation/execution stages of REXX statements (clauses, values, etc.), including comments and also blank lines). The trace statement is also used for interactive debugging.
Nested comments must have matching delimiters, so the contents of the comments can't just be willy-nilly characters.
Also, some REXX interpreters show the comment (if part of a REXX statement) as part of the information displayed when (if) a syntax error occurs and an informative error message is generated. For instance, in the program (named c:\COMMENTD.REX):
<lang rexx>/*REXX program that demonstrates what happens when dividing by zero. */
y=7
say 44 / (7-y) /* divide by some strange thingy.*/</lang>
output when using the Regina REXX interpreter:'
3 +++ say 44 / (7-y) /* divide by some strange thingy.*/ Error 42 running "c:\COMMENTD.REX", line 3: Arithmetic overflow/underflow Error 42.3: Arithmetic overflow; divisor must not be zero
output when using the R4 REXX interpreter:'
Error 42 : Arithmetic overflow/underflow (SYNTAX) Information: Divide by zero Error occurred in statement# 3 Statement source: say 44/(7-y) Statement context: c:\commentdv.rex, procedure: commentdv
output when using the Personal REXX interpreter:'
3 +++ say 44 / (7-y) /* divide by some strange thingy.*/ Error 42 on line 3 of C:\COMMENTD.REX: Arithmetic overflow/underflow
The REXX language was heavily modeled after PL/I, both languages have the same comment construct, but PL/I doesn't support nested comments.
Nested comments allow an easy way to comment large chunks of code where the commented-out code has its own comments.
<lang rexx>/*REXX program to demonstrate various uses and types of comments. */
/* everything between a "climbstar" and a "starclimb" (exclusive of literals) is
a comment.
climbstar = /* [slash-asterisk]
starclimb = */ [asterisk-slash]
/* this is a nested comment, by gum! */
/*so is this*/
Also, REXX comments can span multiple records.
There can be no intervening character between the slash and asterisk (or the asterisk and slash). These two joined characters cannot be separated via a continued line, as in the manner of:
say 'If I were two─faced,' ,
'would I be wearing this one?' ,
' --- Abraham Lincoln'
Here comes the thingy that ends this REXX comment. ───┐
│
│
↓
*/
hour = 12 /*high noon */
midnight = 00 /*first hour of the day */
suits = 1234 /*card suits: ♥ ♦ ♣ ♠ */
hutchHdr = '/*' hutchEnd = "*/"
/* the previous two "hutch" assignments aren't
the start nor the end of a REXX comment. */
x=1000000 ** /*¡big power!*/ 1000
/*not a real good place for a comment (above),
but essentially, a REXX comment can be anywhere whitespace is allowed. */</lang>
A Classic REXX implementation (e.g. Regina) also allow line comments which start with a -- sequence and extend to the end of the line:
[Note: Regina REXX releases since 3.4 allow this type of single-line comment only if the option Single_Line_comments isn't present in the REGINA_OPTIONS environmental variable. So, Regina may allow the use of single-line comments, depending upon which release is being used. That is to say, one can't depend (or assume) that the Regina extension (of single-line comments) for the aforementioned option will be or not be present (supported and/or allowed) in the environment being used]. Which means one could set this option to their preference if using Regina REXX later than version 3.3.
Since Single-Line comments aren't part of the ANSI standard nor a part of the Classic REXX language, the use of which would make the REXX code non-portable.]
<lang rexx>-- A REXX line comment (maybe) say "something" -- another line comment (maybe)</lang> It should be noted that the above type of comments are not part of Classic REXX, nor are they described nor sanctioned in the REXX ANSI standard.
Ring
in Ring language we can use // or # for one line comments: <lang ring> //this is a single line comment
- this also a single line comment!
</lang>
and for multi-line comments we use /* */: <lang ring> /*This is a multi-line comment that will be completely ignored by the compiler/interpreter
- /
</lang>
RLaB
RLaB only has single line comment indicator, as in following examples
<lang RLaB> x = "code" # I am a comment x = "code" // Here I comment thee
- matlab-like document line
// C++ like document line </lang>
Robotic
Comments can only be created in one way: <lang robotic> . "This is a comment line"
. "Print Hello world"
- "Hello world."
. "This is the only way to comment a line in Robotic" </lang>
Although these are comments, the interpreter doesn't completely ignore it. For one, the code speed can be affected if they are ever encountered. Also, if an @ character exists at the beginning of the comment line, then the rest of the string after it is now the Robot's new name (there is a 14 character limit).
Example of changing the robot's name: <lang robotic> . "@NewRobotName" </lang>
This would then change the robot's name from whatever it was before to "NewRobotName" instead.
Ruby
<lang ruby>x = "code" # I am a comment
=begin hello I a POD documentation comment like Perl =end puts "code"</lang>
Run BASIC
Comments have a ' (single quote) or REM for remarks <lang runbasic>'This is a comment REM This is a comment
print "Notice comment at the end of the line." 'This is a comment print "Also notice this comment at the end of the line." : REM This is a comment </lang>
Rust
<lang rust>// A single line comment
/*
This is a multi-line (aka block) comment
/*
containing nested multi-line comment
(nesting supported since 0.9-pre https://github.com/mozilla/rust/issues/9468)
*/
- /
/// Outer single line Rustdoc comments apply to the next item.
/**
Outer multi-line Rustdoc comments.
* Leading asterisk (*) in multi-line Rustdoc comments * is not considered to be part of the comment text, * blanks and tabs preceding the initial asterisk (*) are also stripped.
- /
fn example() {
//! Inner single line Rustdoc comments apply to their enclosing item.
/*!
Inner multi-line Rustdoc comments.
See also https://github.com/mozilla/rust/wiki/Doc-using-rustdoc
*/
}
- [doc = "Unsugared outer Rustdoc comments.
(outer attributes are not terminated by a semi-colon)"]
fn example() {
#[doc = "Unsugared inner Rustdoc comments.
(inner attributes are terminated by a semi-colon)
See also https://github.com/mozilla/rust/blob/master/doc/rust.md#attributes"];
}</lang>
SAS
<lang sas>/* comment */
- another comment;
- both
may be multiline;</lang>
Sather
<lang sather>-- a single line comment</lang>
Scala
<lang scala>// A single line comment
/* A multi-line
comment */</lang>
Scheme
<lang scheme>; Basically the same as Common Lisp
- While R5RS does not provide block comments, they are defined in SRFI-30, as in Common Lisp
- | comment
... #| nested comment ... |# |#
</lang>
Scilab
Specify a comment starting with // to the end of line <lang>// this is a comment i=i+1 // this is a comment</lang>
sed
<lang sed># a single line comment</lang>
Seed7
<lang seed7># A single line comment
(* A multi-line
comment *)
(* In Seed7, (* comments can be nested. *) *)</lang>
SenseTalk
<lang sensetalk>
- Hashtag is a comment
-- Dash dash is another comment // Slash slash is yet another comment — Alt/Option + Underscore creates an m-dash comment (* Parentheses and star is used for commenting blocks of code (* and can be nested *) *) set foo to true // all comments can append to statements </lang>
Set lang
<lang set_lang>> Comments start where a > (greater than symbol) starts set a 0 > Comments may start after a Set command</lang>
SETL
<lang setl>print("This is not a comment"); -- This is a comment $ For nostalgic reasons, this is also a comment.</lang>
Sidef
Single line comment <lang ruby># this is commented</lang>
These may also be at the end of a line <lang ruby>var i = 1; # this is the comment part</lang>
Embedded comments <lang ruby>var distance #`{in meters} = (30 #`{meters} * 100 #`{seconds}); say distance; # prints: 3000</lang>
Multi-line comments <lang ruby>/*
This is a multi-line comment
- /</lang>
Simula
The same as Algol 60: <lang>COMMENT This is a comment for Simula 67;</lang> And an new form: <lang>!This is a comment for Simula 67;</lang> Pitfall: it's not easy to comment-out parts of code: <lang Simula>!OutText("Dying."); !Outimage; !terminate_program;</lang>
Slate
<lang slate>"basically the same as smalltalk"</lang>
Smalltalk
<lang smalltalk>"Comments traditionally are in double quotes." "Multiline comments are also supported.
Comments are saved as metadata along with the source to a method. A comment just after a method signature is often given to explain the usage of the method. The class browser may display such comments specially."</lang>
smart BASIC
<lang>'Single line comments are preceded by a single quote or the command REM
PRINT "Hello" 'Single line comments may follow code
PRINT "Hello" REM You can also use the command REM following code
/* Multi-line comments are surrounded by mirrored slash and asterisk
- /
/*Multi-line comments do not have to actually have multiple lines*/
/* Spaces before or after comment bounds are optional.*/
/* A comment can also follow another comment */ 'Like this
Some programmers like to do this to allow for /* Procedural comments */ followed by 'Programmer's notes.</lang>
SNOBOL4
<lang SNOBOL4>
- An asterisk in column 1 is the standard Snobol comment
- mechanism, marking the entire line as a comment. There
- are no block or multiline comments.
- Comments may begin at
- any position on the line.
- A hyphen in column 1 begins a control statement. - Unrecognized control statements are ignored and - may also mark comment lines. Not recommended.
;* The semicolon statement separator
output = 'FOO' ;* begins a new statement. This idiom
output = 'BAR' ;* simulates an asterisk in the first
;* column, allowing end of line comments.
END
Any text after the required END label is ignored.</lang>
SNUSP
As with Brainf*** and Befunge, any character that is not part of the language is ignored and can be used as commentary, and you can add comments anywhere the instruction pointer is not expected to traverse. Reserved characters are:
- Core: + - > < , . ? ! / \ $ #
- Modular: @ #
- Bloated: : ; & %
As a matter of convention, the characters '=' and '|' are used for spacing to indicate horizontal and vertical flow of control, respectively.
SPL
<lang spl>'This is single-line comment
This is multiline comment</lang>
SQL
The double hyphen ( -- ) is used to include a comment on an SQL statement.
The comment appears on the same line as the statement: <lang sql>SELECT * FROM mytable -- Selects all columns and rows</lang> or before: <lang sql>-- Selects all columns and rows SELECT * FROM mytable </lang> or after: <lang sql>SELECT * FROM mytable -- Selects all columns and rows</lang>
SQL PL
Single line comment:
<lang sql pl> --This is a single line comment. </lang>
Multiline comment:
<lang sql pl> /* This is a multiline comment */ </lang>
Another way to do multiline comments
<lang sql pl> (= This is a multiline comment =) </lang>
End of line comment:
<lang sql pl> declare myvar number; --This is an end of line comment. </lang>
Comments work the same as in SQL.
Squirrel
<lang squirrel>//this is a single line comment
- this is also a single line comment
/*
this is a multi-line comment
- /</lang>
SSEM
The SSEM can only be programmed in pure binary, by setting front panel switches: the concepts of "text" and "source file" (both mentioned in the specification) are therefore not directly applicable to it. If binary numbers have any mnemonic or explanatory value for you, however, there is a way of including information in your program that the computer will ignore. This is a direct result of the machine's rather poor code density. Each 32-bit instruction word consists of (a) a five-bit address field giving the operand, (b) eight unused bits, (c) a three-bit instruction field giving the operation to be performed, and (d) sixteen more unused bits. If the instruction field is set to 011 Test or 111 Stop, even the address field is unused. In the case of a Sub. instruction, finally, the leftmost bit of the instruction field is disregarded: 001 and 101 both mean "subtract". We therefore have at least 24 and sometimes 25 or 29 bits in each instruction that we can, if we like, use for comments. The word <lang ssem>00101010010001000100100100001100</lang> will be understood by the machine as Add 20 to CI, a normal instruction. But it also fits four comment characters into the unused bits, employing a simple five-bit encoding where A=0 and Z=25. The instruction breaks down as follows:
00101 -- address field = 20
01001 -- "comment" field = 18
000 -- three unused bits
100 -- instruction field = Add to CI
01001 -- "comment" field = 18
00100 -- "comment" field = 4
01100 -- "comment" field = 12
0 -- unused bit
Applying our simple alphabetic encoding, we see that the "spare" bits spell out 18, 18, 4, 12 = S, S, E, M.
More realistically, you can include comments when you are drafting your program using mnemonic notation and then simply leave the comments out when it comes time to toggle the program in.
Standard ML
<lang sml>(* This a comment
(* containing nested comment *) *)</lang>
Stata
<lang stata>* Line comment: must be used at the beginning of a line (does not work in Mata)
// Line comment until the end of the line
/* Multiline comment
- /</lang>
Swift
<lang swift>// this is a single line comment /* This a block comment
/* containing nested comment */ */
///This is a documentation comment
/**
This is a documentation block comment
- /</lang>
Symsyn
<lang Symsyn> | This is a comment </lang>
Tcl
Tcl follows the usual scripting language rules: a comment starts at a "#" symbol, which can be placed after a command if that is terminated by a semicolon:
<lang tcl># comment on a line by itself. The next is a command by itself: set var1 $value1 set var2 $value2 ; # comment that follows a line of code</lang>
The reason for the need for a semi-colon on a trailing comment is this:
"If a hash character (“#”) appears at a point where Tcl is expecting the first character of the first word of a command, then the hash character and the characters that follow it, up through the next newline, are treated as a comment and ignored. The comment character only has significance when it appears at the beginning of a command." (from the Tcl man page -- emphasis mine)
The "#" symbol has no special meaning if it is not where a command would appear -- it's just data. (Syntax highlighters often get this wrong.)
<lang tcl>set aList {foo} lappend aList # bar puts $aList ;# ==> prints "foo # bar" puts [llength $aList] ;# ==> 3</lang>
TCL has no native multi-line comment format. However, in most circumstances, a multi-line comment can be faked by wrapping it within a block that will never be executed:
<lang tcl>if 0 {
Comments...
}</lang>
Tern
- See Java
TI-83 BASIC
There is no 'proper' way of adding comments in TI-BASIC, however there are ways to add text to a program that will be ignored by the calculator.
One common approach is to put the comment in a string which is not stored anywhere: <lang ti83b>:"THIS IS A COMMENT</lang> However this will change the Ans variable.
This approach, while messier, does not affect the Ans variable: <lang ti83b>:If 0
- THIS IS A COMMENT</lang>
TI-89 BASIC
<lang ti89b>© This is a comment. Everything from © to the end of the line is ignored.</lang>
Tiny BASIC
<lang Tiny BASIC> 10 REM this is a comment 20
40 REM from above you can see that line numbers with no statement 50 REM and blank lines also are ignored </lang>
Toka
There are two ways to add comments in Toka. For full lines, or at the end of a line, the shebang is normally used:
<lang toka>#! Everything on this line (after the shebang to the left) will be ignored.</lang>
The shebang comments can not be used inside of functions.
In addition, Toka also accepts parenthetical comments. These are enclosed in parenthesis, and are often used for stack comments or comments inside functions.
<lang toka>[ ( a b -- c )
... ] is myword</lang>
In addition, parenthetical comments can span multiple lines.
<lang toka>( This is a
simple, multi-line comment )</lang>
Since comments are provided by actual functions, the comment function must be whitespace delimited, just as with all other functions in Toka.
A final way to include text in a file is to mark a false ending with end.
<lang toka>... code .... end. Nothing following the end. will be evaluated by Toka.</lang>
TorqueScript
<lang TorqueScript>//This is a one line comment. There are no other commenting options in TorqueScript.</lang>
TPP
<lang tpp>--## comments are prefixed with a long handed double paintbrush</lang>
Transd
<lang scheme>// This is a line comment. /* This is a single line block comment.*/ /* This is
a multi-line block comment.*/
</lang>
TUSCRIPT
<lang tuscript> $$ MODE TUSCRIPT - This is a comment </lang>
TXR
<lang txr>@# old-style comment to end of line @; new-style comment to end of line @(bind a ; comment within expression
"foo")</lang>
UNIX Shell
<lang bash>#!/bin/sh
- A leading hash symbol begins a comment.
echo "Hello" # Comments can appear after a statement.
- The hash symbol must be at the beginning of a word.
echo This_Is#Not_A_Comment
- Comment</lang>
C Shell
<lang csh>#!/bin/csh -f
- C Shell has a similar comment syntax, but only allows comments in a
- script file, not in terminal input.
echo Hello#With C Shell, the hash can also be in the middle of a word.</lang>
es
<lang es># Comments in es (extensible shell) look like those of other shells.
echo Hello#With es, the hash can also be in the middle of a word.</lang>
Unlambda
Unlambda comments start with # and extend to the end of the line:
# this is a comment.
Note that comments don't need to start at the beginning of a line, e.g.
` # apply .a # output "a" i # identity
is equivalent to
`.ai
Ursa
Comments in Ursa must be on a single line, and are denoted by a # <lang ursa># this is a comment
- this is another comment
</lang>
Ursala
There are lots of ways to have comments in Ursala. Here are the conventional ones. <lang Ursala># this is single line a comment
- this is a\
continued comment
(# this is a multi-line comment #)
(# comments in (# this form #) can (# be (# arbitrarily #) #) nested #)
this is also a comment\
and can be continued
The whole rest of the file after three hashes is a comment.</lang>
Commenting out code
There are also ways to comment out sections of code during testing. An individual item of a syntactically correct list or aggregate is commented out like this. <lang Ursala>x = <1,## 2,3></lang> The 2 is ignored but 1 and 3 aren't. This also works with nested aggregates and multiple lines. <lang Ursala>a =
<
'to',
## <
'be',
'or'>,
'not',
'to',
## 'be'></lang>
A syntactically correct declaration can be commented out like this. <lang Ursala>foo = 1
bar = 2
baz = 3</lang> As far as the compiler is concerned, bar is not defined, but foo and baz are. It wouldn't matter if bar took multiple lines.
Comments in compiled files
The compiler can be directed to embed comments in executable files and libraries it generates without affecting their semantics. <lang Ursala>#comment -[ I document the source text but will also be embedded in the output library or executable file.]-
- comment gpl'3'</lang>
The latter comment puts the standard GPL license notification in the output file.
Comments as diagnostics
A function f annotated with a crash dump wrapper expressed like this during debugging <lang Ursala>my_input_type%C f</lang> is equivalent to just f when changed to this in the production code. <lang Ursala>my_input_type%Ck f</lang>
Comments as hooks
Compiling with the --depend command line option makes the compiler only scan for the #depend'ed expressions and send them to standard output. <lang Ursala>#depend <this,expression> is (parsed)* but {
otherwise, ignored}</lang>
This way, scripts and source management tools can have information passed to them from the programmer by running the compiler instead of re-implementing their own parsers.
VBA
A comment starts with a quote (') and it ends at end of line <lang vb>' This is a VBA comment </lang>
VBScript
A comment starts with a quote (') and it ends at end of line <lang vb>' This is a VBScript comment </lang>
Verbexx
<lang verbexx> ////////////////////////////////////////////////////////////////////////////////////////////// // // Line Comments: // ============= // @VAR v1 = 10; // Line comments start from the "//" and continue to end of the line. // (normal code can appear on the same line, before the //) // // Line comments can span a complete line, or start in the middle of a line. /// //// Additional // chars and /* /* /[ ]/ and /] are ignored //// Line comments can be appear to be nested, since any additional // is ignored. /// // Note: // can appear in strings without triggering a line comment // // cannot appear inside an operator (or verbname), since a line comment // would start // /////////////////////////////////////////////////////////////////////////////////////////////
/********************************************************************************************
* * Block Comments: * ============== * ********************************************************************************************/
//* //* These start with /* and end with the next */ . They cannot be nested, since the first */ //* will end the block comment. For example, the comment, /* /* */ */ would end after the //* first */. Note that /* is ignored inside a block comment, as are // /[ /] and /]. //* //* Also note that something like the following will cause trouble in a block comment: //* //* /* comments // //* * more comments // */ (the // does not prevent the */ from ending //* * (no longer part of the comment) // block comment) //* */ //* //* Note: /* can appear in strings without triggering the start of a block comment //* /* cannot appear inside an operator (or verbname), since a line comment will //* start, although */ is allowed inside an operator (verbname). Commenting //* out such a verbname may cause problems. //* //* Note: Since string literals are not recognized in block comments, */ appearing //* in a string literal inside a block comment (perhaps commented-out code) //* will cause the block comment to end. //* //* Note: It is an error to start a block comment and not end it, so that it is still //* in progresss when the end-of-file is reached. //* //* Block comments can appear inside lines of code: //* /*1*/@VAR/*2*/v2/*3*/=/*4*/20/*5*/;/*6*/ // a line comment can follow block comments on the
// same line
/[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][] /[] [] /[] Nestable Block Comments: []
[] ======================== []/ [] []/ [][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]/
//[] //[] These start with /[ and end with the next matching ]/ . Additional occurrences //[] of /[ ... ]/ can appear inside a nestable block comment. The nestable block comment //[] will end only when the nest level reaches 0. Note that /* is ignored inside a nestable //[] block comment, as are */ // and /]. //[] //[] Nestable block comments can be used to comment out blocks of code containing line //[] comments or regular comments, and even balanced and well-formed nestable block comments. //[] //[] Note: /[ can appear in strings without triggering the start of a block comment. //[] However, strings literals are not recognized inside a nestable block comment, so //[] any appearances of /[ and /] inside a string literal in a nestable block commment //[] will affect the nest level, and may cause problems. //[] //[] Note: It is an error to start a nestable block comment and not end it, so that it is //[] still in progresss when the end of file is reached. //[] //[] Nestable block comments can appear inside lines of code: //[] /[1]/@VAR/[2]/v3/[3]/=/[4]/30/[5]/;/[6]/ // a line comment can follow nestable block comments
// on the same line
@SAY v1 v2 v3; // should see: 10 20 30
/] /=================================================================================================\ | | | /] starts a block comment that lasts until the end of the current file. Everything after | | the /] is ignored. | | | \=================================================================================================/ </lang>
Verilog
<lang Verilog>// Single line commment.
/*
Multiple line comment.
- /</lang>
VHDL
<lang vhdl>-- Single line commment in VHDL</lang>
Vim Script
All lines starting with " are comments and will be ignored.
In most cases, " will also work after a command (i.e. the rest of the line will be ignored). But some commands like echo treat the whole line as their argument and thus will raise an error (Missing quote).
<lang vim>let a = 4 " A valid comment echo "foo" " Not a comment but an argument that misses the closing quote</lang>
Visual Basic
In addition to the methods mentioned in BASIC above, it is also somewhat common to effectively comment out code by including the unwanted code inside an #If 0 ... #End If block. (This works because 0 evaluates to False in VB.) Note, however, that the IDE will complain about actual comments inside an #If 0 block unless it's also commented normally (i.e., using Rem or ').
<lang vb>'comment Rem comment
- If 0
Technically not a comment; the compiler may or may not ignore this, but the IDE won't. Note the somewhat odd formatting seen here; the IDE will likely just mark the entire line(s) as errors.
- End If</lang>
Visual Basic .NET
Visual Basic .NET uses the "'" symbol or "REM" to mark it's comments. After placing a "'", or "REM", everything in that line will be ignored.
<lang vbnet>' This is a comment REM This is also a comment Dim comment as string ' You can also append comments to statements Dim comment2 as string REM You can append comments to statements</lang>
Visual Objects
<lang visualfoxpro> // This is a comment /* This is a comment */
- This is a comment
&& This is a comment NOTE This is a commen
</lang>
Vlang
// This is a single line comment. /* This is a multiline comment. /* It can be nested. */ */
Vorpal
<lang vorpal># single line comment</lang>
Wart
<lang wart># single-line comment</lang>
Wren
<lang ecmascript>// This is a line comment. /* This is a single line block comment.*/ /* This is
a multi-line block comment.*/
/* This is/* a nested */block comment.*/</lang>
X10
All text included within the ASCII characters “/*” and “*/” is considered a comment and ignored; nested comments are not allowed.
All text from the ASCII characters “//” to the end of line is considered a comment and is ignored. <lang X10>// This is a single line comment
/*
This comment spans multiple lines
- /</lang>
XLISP
<lang xlisp>; this is a comment</lang>
Xojo
<lang VB> // Comments are denoted by a preceding double slash or or single quote ' and continue to the end of the line. There are no multi-line comment blocks Dim foo As Integer // Comments can also occupy the ends of code lines</lang>
XPL0
Comments are enclosed in backslash characters, but the end of a line always terminates a comment. Consequently there is no multi-line comment. For example: <lang XPL0>Text(0, \comment\ "Hello \not a comment\ World!"); \comment</lang>
Since backslashes toggle comments on and off, it could be inconvenient to comment out a line of code that contains a comment. For example, two additional backslashes could be used to comment out this line, as shown here: <lang XPL0> Text(0, "Hello World"); \comment \Text(0, "Hello World"); \\comment</lang>
However, two backslashes together comment out everything to the end of the line regardless of any backslashes the line might contain. So the first example could be commented out like this: <lang XPL0>\\Text(0, \comment\ "Hello \not a comment\ World"); \comment</lang>
Conditional compilation can be used to effectively comment out multiple lines of code. For example: <lang XPL0>cond false; Text(0, "Hello World"); \comment CrLf(0); cond true;</lang>
XQuery
<lang xquery>(: This is a XQuery comment :)</lang>
XSLT
<lang xml></lang>
XUL
<lang xul></lang>
Yacas
Yacas supports C++ style comments: <lang Yacas>// This is a single line comment /*
This comment spans multiple lines
- /</lang>
Z80 Assembly
Note: syntax depends on the assembler software but use of a semicolon is fairly standard. VASM and WinAPE use the semicolon. <lang z80> ld hl,&8000 ;This is a comment</lang>
zig
<lang zig>// This is a normal comment in Zig /// This is a documentation comment in Zig (for the following line)</lang>
zkl
<lang zkl>x=1; // comment ala C++ x=2; # ala scripts /* ala C, these comments are parsed (also ala C) */ /* can /* be */ nested */
- if 0
also ala C (and parsed)
- endif
- <<<#
"here" comment, unparsed
- <<<#</lang>
Zoea
<lang Zoea> program comments # this program does nothing
- zoea supports single line comments starting with a '#' char
/*
zoea also supports multi line comments
- /
</lang>
Zoea Visual
zonnon
<lang zonnon> (* this is a comment *) (*
and this is a multiline comment (* with a nested comment *)
- )
</lang>
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