Unicode variable names: Difference between revisions

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Describe, and give a pointer to documentation on your languages use of characters beyond those of the ASCII character set in the naming of variables.
Show how to:

Set a variable with a name including the 'Δ', (delta character), to 1
Increment it
Print its value.

Cf.

Case-sensitivity of identifiers

AutoHotkey

The earlier version of AutoHotkey (AutoHotkey Basic) will produce an error since it doesn't support Unicode. It is perfectly working in AutoHotkey_L Unicode (Lexikos Custom Build). Documentation: http://www.autohotkey.net/~Lexikos/AutoHotkey_L/docs/Variables.htm

Works with: AutoHotkey_L

<lang ahk>Δ = 1 Δ++ MsgBox, % Δ</lang>

C

C has limited support for Unicode in variable names, see Annex D of the C standard.

D

D source files support four character encodings: ASCII, UTF-8, UTF-16 and UTF-32. <lang d>import std.stdio;

void main() {

   auto Δ = 1;
   Δ++;
   writeln(Δ);

}</lang> You can use any of the following:

   Letters,
   digits,
   underscore (_),
   code points >= \u00A0 and < \uD800,
   code points > \uDFFF.

However, the following cannot be used:

   \u0024 ($),
   \u0040 (@) and
   \u0060 (`).

See: http://www.prowiki.org/wiki4d/wiki.cgi?DanielKeep/TextInD

Delphi

For more information about naming identifiers (including variables) visit: Identifiers in Delphi <lang Delphi>(* Compiled with Delphi XE *) program UnicodeVariableName;

{$APPTYPE CONSOLE}

uses

 SysUtils;

var

 Δ: Integer;

begin

 Δ:= 1;
 Inc(Δ);
 Writeln(Δ);
 Readln;

end.</lang>

DWScript

<lang Delphi>var Δ : Integer;

Δ := 1; Inc(Δ); PrintLn(Δ);</lang>

Forth

Historically, Forth has worked only in ASCII (going so far as to reserve the eighth bit for symbol smudging), but some more modern implementations have extended character set support such as UTF-8.

Works with: GNU Forth

0.7.0

<lang forth>variable ∆ 5 ∆ ! ∆ @ .</lang>

Go

Go source encoding is specified to be UTF-8. Allowable variable names are specified in the sections identifiers and Exported identifiers. <lang go>package main

import "fmt"

func main() {

   Δ := 1
   Δ++
   fmt.Println(Δ)

}</lang> Output:

Haskell

Haskell variables must start with a lower case character, however Δ is an upper case delta. As such, lower case delta (δ) was used as the first character instead, followed by an upper case delta as the second character in the variable name.

Also, Haskell does not allow mutable variables, so incrementing delta isn't possible. Instead lower case psi was used to store the incremented value of delta since tridents are cool.

<lang Haskell>main = print ψ

   where δΔ = 1
         ψ = δΔ + 1</lang>

Java

<lang java>int Δ = 1; double π = 3.141592; String 你好 = "hello"; Δ++; System.out.println(Δ);</lang> Output:

Mathematica

<lang Mathematica>Δ = 1; Δ++; Print[Δ]</lang>

PARI/GP

GP accepts only ASCII in strings and variable names.

PARI supports Unicode variable names only insofar as C does.

Perl

Requires Perl 5.8.1 at the minimum. See http://perldoc.perl.org/utf8.html

<lang perl>use utf8; my $Δ = 1; $Δ++; print $Δ;</lang>

One can have Unicode in identifier names, but not in package/class or subroutine names. While some limited functionality towards this does exist as of Perl 5.8.0, that is more accidental than designed; use of Unicode for the said purposes is unsupported.

One reason of this unfinishedness is its (currently) inherent unportability: since both package names and subroutine names may need to be mapped to file and directory names, the Unicode capability of the filesystem becomes important-- and there unfortunately aren't portable answers.

Perl 6

Perl 6 is written in Unicode so, with narrow restrictions, nearly any Unicode letter can be used in identifiers.

See Perl 6 Synopsis 02. - http://perlcabal.org/syn/S02.html#Names

Function and subroutine names can also use Unicode characters: (as can methods, classes, packages, whatever...)

<lang perl6>my @ᐁ = (0, 45, 60, 90);

sub π { pi };

sub postfix:<°>($degrees) { $degrees * π / 180 };

for @ᐁ -> $ಠ_ಠ { say sin $ಠ_ಠ° };</lang>

PicoLisp

Variables are usually Internal Symbols, and their names may contain any UTF-8 character except null-bytes. White space, and 11 special characters (see the reference) must be escaped with a backslash. Transient Symbols are often used as variables too, they follow the syntax of strings in other languages. <lang PicoLisp>: (setq Δ 1) -> 1

Δ

-> 1

(inc 'Δ)

-> 2

Δ

-> 2</lang>

PHP

PHP is not made to support Unicode. UTF-16 (UCS-2) will not work because it adds null bytes before or after ASCII characters (depending on endianness of UTF-16). As every code has to start with <?php (ASCII) exactly, the parser doesn't find the match and just prints <?php mark.

UTF-8 uses ASCII values for bytes which can be represented as ASCII and as result it's possible to insert <?php mark at beginning. PHP sees your document as some 8-bit encoding (like ISO-8859-1), but it doesn't matter because UTF-8 doesn't use ASCII ranges for its values and calls to the variable are consistent.

Documentation: http://php.net/manual/en/mbstring.php4.req.php, http://php.net/manual/en/language.variables.basics.php

Protium

This example is incomplete. Please ensure that it meets all task requirements and remove this message.

1. (working on it)

2. <lang protium><@ LETVARLIT>Δ|1</@> <@ ACTICRVAR>Δ</@> <@ SAYVAR>Δ</@></lang>

Using what Google Translate says is the Traditional Chinese for 'delta' <lang protium><@ LETVARLIT>三角洲|1</@> <@ ACTICRVAR>三角洲</@> <@ SAYVAR>三角洲</@></lang>

Python

Within the ASCII range (U+0001..U+007F), the valid characters for identifiers are the same as in Python 2.x: the uppercase and lowercase letters A through Z, the underscore _ and, except for the first character, the digits 0 through 9.

Python 3.0 introduces additional characters from outside the ASCII range (see PEP 3131). For these characters, the classification uses the version of the Unicode Character Database as included in the unicodedata module.

Identifiers are unlimited in length. Case is significant.

<lang python>>>> Δx = 1 >>> Δx += 1 >>> print(Δx) 2 >>> </lang>

Retro

This has been tested on Retro 11.0 running under OS X.

<lang Retro>variable Δ 1 !Δ @Δ putn 1 +Δ @Δ putn</lang>

Function and variable names are stored as strings, and UTF-8 is usable, as long as the host system allows it.

Ruby

This task requires Ruby 1.9. Multilingualization, or m17n, is a major new feature of Ruby 1.9. With m17n, the identifiers can use the non-ASCII characters. Ruby is a Code Set Independent (CSI) language, so there are many different character encodings, not only Unicode.

Any non-ASCII characters require a magic comment to select the encoding.
Ruby source code must be ASCII compatible. For example, SJIS and UTF-8 are ASCII compatible, but ISO-2022-JP and UTF-16LE are not compatible. So one can write the source file in UTF-8, but not in UTF-16LE.

A more complete reference is The design and implementation of Ruby M17N.

The next example uses a magic comment to select the Big5 encoding. Then it creates a local variable named Δ.

Works with: Ruby version 1.9

<lang ruby># -*- coding: big5 -*- Δ = 1 Δ += 1 puts Δ</lang>

00000000  23 20 2d 2a 2d 20 63 6f  64 69 6e 67 3a 20 62 69  |# -*- coding: bi|
00000010  67 35 20 2d 2a 2d 0a a3  47 20 3d 20 31 0a a3 47  |g5 -*-.Δ = 1.Δ|
00000020  20 2b 3d 20 31 0a 70 75  74 73 20 a3 47 0a        | += 1.puts Δ.|
0000002e

The output is 2.

One can also use the non-ASCII characters in a method name. The next example selects the EUC-JP encoding, and creates a method named ≦, with a parameter named ♯♭♪. Because ≦ is an ordinary method, not an operator, so the program must use a dot to call the method.

Works with: Ruby version 1.9

<lang ruby># -*- coding: euc-jp -*-

class Numeric

 def ≦(♯♭♪)
   self <= ♯♭♪
 end

end

∞ = Float::INFINITY ±5 = [-5, 5] p [(±5.first.≦ ∞),

  (±5.last.≦ ∞),
  (∞.≦ ∞)]</lang>

00000000  23 20 2d 2a 2d 20 63 6f  64 69 6e 67 3a 20 65 75  |# -*- coding: eu|
00000010  63 2d 6a 70 20 2d 2a 2d  0a 0a 63 6c 61 73 73 20  |c-jp -*-..class |
00000020  4e 75 6d 65 72 69 63 0a  20 20 64 65 66 20 a1 e5  |Numeric.  def ≦|
00000030  28 a2 f4 a2 f5 a2 f6 29  0a 20 20 20 20 73 65 6c  |(♯♭♪).    sel|
00000040  66 20 3c 3d 20 a2 f4 a2  f5 a2 f6 0a 20 20 65 6e  |f <= ♯♭♪.  en|
00000050  64 0a 65 6e 64 0a 0a a1  e7 20 3d 20 46 6c 6f 61  |d.end..∞ = Floa|
00000060  74 3a 3a 49 4e 46 49 4e  49 54 59 0a a1 de 35 20  |t::INFINITY.±5 |
00000070  3d 20 5b 2d 35 2c 20 35  5d 0a 70 20 5b 28 a1 de  |= [-5, 5].p [(±|
00000080  35 2e 66 69 72 73 74 2e  a1 e5 20 a1 e7 29 2c 0a  |5.first.≦ ∞),.|
00000090  20 20 20 28 a1 de 35 2e  6c 61 73 74 2e a1 e5 20  |   (±5.last.≦ |
000000a0  a1 e7 29 2c 0a 20 20 20  28 a1 e7 2e a1 e5 20 a1  |∞),.   (∞.≦ |
000000b0  e7 29 5d 0a                                       |)].|
000000b4

The output is [true, true, true] because the numbers -5, 5 and infinity are all less than or equal to infinity.

Tcl

Tcl variable names can include any character (the $var syntax can't, but that's just a shorthand). Thus, this script is entirely legal: <lang tcl>set Δx 1 incr Δx puts [set Δx]</lang> However, this script only works smoothly if the “Δ” character is in the system's default encoding (thankfully more common than it used to be, as more and more systems use UTF-8 or UTF-16 as their default encodings) so normal Tcl practice is to stick to ASCII for identifier names.