Unicode variable names

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Unicode variable names
You are encouraged to solve this task according to the task description, using any language you may know.
  1. 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.
  2. Show how to:
  • Set a variable with a name including the 'Δ', (delta character), to 1
  • Increment it
  • Print its value.


[edit] 8th

Text in 8th is stored in the UTF-8 encoding, which means that the text is always represented correctly, even when due to other issues (e.g. font problems) it may appear incorrect.

To make the programmer’s task easier, 8th not only lets you actually enter any UTF-8 text, it also lets you use special “escapes” in your text to make it easier to enter obscure characters. Thus, for example, this string: "qu\u00e9" results in this: qué.

The words (e.g. “functions”) 8th provides to do string manipulation are also UTF-8 aware, which means you don’t have to worry about creating an invalid bit of UTF-8 encoded text (unless you deliberately do so).

-- Writing localized applications with 8th

1 var, Δ
Δ @ n:1+ Δ !
Δ @ . cr
\ unicode silliness
: 念 ' G:@ w:exec ;
: 店 ' G:! w:exec ;
: ਵਾਧਾ ' n:1+ w:exec ;
: الوداع ' G:bye w:exec ;
: キャリッジリターン ' G:cr w:exec ;
: प्रिंट ' G:. w:exec ;
Δ 念 ਵਾਧਾ Δ 店
Δ 念 प्रिंट キャリッジリターン

[edit] ACL2

Variables in ACL2 cannot be modified in place.

(let ((Δ 1))
(1+ Δ))

[edit] Ada

As of Ada 2005, all source code can be made of up to 32bit characters. Unless you have made it a default, GNAT would require the -gnatW8 flag to understand you are using UTF8 for the code below, other encodings are possible.

with Ada.Text_IO;
procedure main is
Δ : Integer;
Δ := 41;
Δ := Δ + 1;
Ada.Text_IO.Put_Line (Δ'Img);
end main;

[edit] 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
Δ = 1
MsgBox, % Δ

[edit] Bracmat

Bracmat allows any sequence of non-zero bytes as symbol and therefore, as variable name. Even the empty string is a variable, though a special one. If a symbol/variable name contains characters that have special meaning (operators, prefixes, parentheses, braces and the semicolon) it may be necessary to enclose it in quotes. Other special characters must be escaped C-style. See bracmat.html in the git-repo. The example below requires a terminal that supports UTF-8 encoded characters.

( (Δ=1)
& 1+!Δ:?Δ
& out$("Δ:" !Δ)


Δ: 2

[edit] C

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

[edit] C#

Section 2.4.2 of the C# Language Specification gives rules for identifiers. They correspond exactly to those recommended by the Unicode Standard Annex 31, except that underscore is allowed as an initial character (as is traditional in the C programming language), Unicode escape sequences are permitted in identifiers, and the "@" character is allowed as a prefix to enable keywords to be used as identifiers.

class Program
static void Main()
var Δ = 1;

[edit] Clojure

According to the current documentation, one should stick to naming with alphanumeric characters and *, +, !, -, _, and ? to avoid possible problems if future versions of Clojure decide to apply special meaning to a character.

That being said, it is not currently enforced, so while you probably shouldn't, you technically can.

(let [Δ 1]
(inc Δ))

[edit] Common Lisp

(let ((Δ 1))
(incf Δ))

[edit] D

D source files support four character encodings: ASCII, UTF-8, UTF-16 and UTF-32.

import std.stdio;
void main() {
auto Δ = 1;

You can use any of the following:

   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

[edit] Delphi

For more information about naming identifiers (including variables) visit: Identifiers in Delphi

(* Compiled with Delphi XE *)
program UnicodeVariableName;
Δ: Integer;
Δ:= 1;

[edit] Déjà Vu

set :Δ 1
set :Δ ++ Δ
!. Δ

[edit] DWScript

var Δ : Integer;
Δ := 1;

[edit] Emacs Lisp

(setq Δ 1)
(setq Δ (1+ Δ))
(message "Δ is %d" Δ)

Variables are symbols and symbol names can be any string. Source code .el files can have all usual Emacs coding system specifications to give variables in non-ASCII.

The byte compiler writes utf-8 (or past versions wrote emacs-mule) into .elc so that any mixture of non-ASCII is preserved.

[edit] F#

As with C# the F# Language Specification refers to Unicode Standard Annex #31 for identifier syntax, allowing Unicode letter characters.

let mutable Δ = 1
Δ <- Δ + 1
printfn "%d" Δ

[edit] 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
variable ∆
5 ∆ !
∆ @ .

[edit] Go

Go source encoding is specified to be UTF-8. Allowable variable names are specified in the sections identifiers and Exported identifiers.

package main
import "fmt"
func main() {
Δ := 1

[edit] 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.

main = print ψ
where δΔ = 1
ψ = δΔ + 1

[edit] J

Variable names must be comprised of ASCII characters.

From the Dictionary page Alphabet and Words:

"The alphabet is standard ASCII, comprising digits, letters (of the English alphabet), the underline (used in names and numbers), ..."
"Names ... begin with a letter and may continue with letters, underlines, and digits."

[edit] Java

int Δ = 1;
double π = 3.141592;
String 你好 = "hello";

[edit] JavaScript

var= "something";
var ĦĔĽĻŎ = "hello";
var 〱〱〱〱 = "too less";
var जावास्क्रिप्ट = "javascript"; // ok that's JavaScript in hindi
var KingGeorgeⅦ = "Roman numerals.";
console.log([, ĦĔĽĻŎ, 〱〱〱〱, जावास्क्रिप्ट, KingGeorgeⅦ])
["something", "hello", "too less", "javascript", "Roman numerals."]

[edit] Julia

The Julia documentation on allowed variable names explicitly describes the wide variety of Unicode codepoints that are allowed:

julia> Δ = 1 ; Δ += 1 ; Δ

The allowed identifiers also include sub/superscripts and combining characters (e.g. accent marks):

julia> Δ̂₂ = Δ^2

and the Julia interactive shells (and many editors) allow typing these symbols via tab-completion of their LaTeX abbreviations.

[edit] LOLCODE

The spec mandates that identifiers be alphanumeric. However, the fact that YARNs are Unicode-aware permits the use of the SRS operator introduced in 1.3 to utilize variables of arbitrary name.

SRS "Δ" R SUM OF SRS ":(394)" AN 1

[edit] Lua

local unicode = {}
unicode["Für"] = "for"
unicode["garçon"] = "boy"

[edit] Mathematica

Δ = 1;

[edit] Nemerle

From the Nemerle Reference Manual: "Programs are written using the Unicode character set, using the UTF-8 encoding."

using System.Console;
module UnicodeVar
Main() : void
mutable Δ = 1;
WriteLine($"Δ = $Δ");

[edit] NetRexx

The NetRexx Language Definition section of the NetRexx documentation (netrexx.org/files/nrl3.pdf) describes the character set support within the language.

/* NetRexx */
options replace format comments java crossref symbols nobinary
upperΔ = 1
Δupper = upperΔ
lowerδ = 2
δlower = lowerδ
say upperΔ '+' Δupper '= \-'
upperΔ = upperΔ + Δupper
say upperΔ
say lowerδ '+' δlower '= \-'
lowerδ = lowerδ + δlower
say lowerδ
-- Unicode works with the NetRexx built-in functions
Υππερ = '\u0391'.sequence('\u03a1') || '\u03a3'.sequence('\u03a9') -- ΑΒΓΔΕΖΗΘΙΚΛΜΝΞΟΠΡΣΤΥΦΧΨΩ
Λοωερ = '\u03b1'.sequence('\u03c1') || '\u03c3'.sequence('\u03c9') -- αβγδεζηθικλμνξοπρστυφχψω
say Υππερ'.Lower =' Υππερ.lower()
say Λοωερ'.Upper =' Λοωερ.upper()
-- Note: Even with unicode characters NetRexx variables are case-insensitive
numeric digits 12
δ = 20.0
π = Math.PI
θ = Π * Δ
σ = Θ ** 2 / (Π * 4) -- == Π * (Δ / 2) ** 2
say 'Π =' π', diameter =' δ', circumference =' Θ', area =' Σ


1 + 1 = 2
2 + 2 = 4

ΑΒΓΔΕΖΗΘΙΚΛΜΝΞΟΠΡΣΤΥΦΧΨΩ.Lower = αβγδεζηθικλμνξοπρστυφχψω
αβγδεζηθικλμνξοπρστυφχψω.Upper = ΑΒΓΔΕΖΗΘΙΚΛΜΝΞΟΠΡΣΤΥΦΧΨΩ

Π = 3.141592653589793, diameter = 20.0, circumference = 62.8318530718, area = 314.159265359

[edit] Nim

From the spec: http://nim-lang.org/docs/manual.html#identifiers-keywords

var Δ = 1

[edit] Objeck

As of 3.2, Objeck supports UTF-8 encoded I/O and stores characters in the runtime's native Unicode format.

class Test {
function : Main(args : String[]) ~ Nil {
Δ := 1;
π := 3.141592;
你好 := "hello";
Δ += 1;

[edit] PARI/GP

GP accepts only ASCII in strings and variable names.

PARI supports Unicode variable names only insofar as C does.

[edit] Perl

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

use utf8;
my= 1;
print, "\n";

$ sigil can be omitted by using lvalue subroutine:

use utf8;
my $val;
sub Δ () : lvalue {
Δ = 1;
print Δ, "\n";

or with Perl 5.10 and state modifier:

use utf8;
use v5.10;
sub Δ () : lvalue {
state $val;
Δ = 1;
say Δ;

One can have Unicode in identifier or subroutine names and also in package or class names. Use of Unicode for the last two purposes is, due to file and directory names, dependent on the filesystem.

[edit] 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

my= 1;

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

my @= (0, 45, 60, 90);
sub π { pi };
sub postfix:<°>($degrees) { $degrees * π / 180 };
for @-> $ಠ_ಠ { say sin $ಠ_ಠ° };

[edit] 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.

: (setq Δ 1)
-> 1
: Δ
-> 1
: (inc 'Δ)
-> 2
: Δ
-> 2

[edit] 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: mbstring.php4.req, language.variables.basics

= 1;

[edit] Prolog

% Unicode in predicate names:
. % be: means, approximately, "True".
不是 :- \+. % not be: means, approximately, "False". Defined as not 是.
% Unicode in variable names:
test(Garçon, Δ) :-
Garçon = boy,
Δ = delta.
% Call test2(1, Result) to have 2 assigned to Result.
test2(Δ, R) :- R is Δ + 1.

Putting this into use:

?- 不是.
?- test(X,Y).
X = boy,
Y = delta.
?- test2(1,Result).
Result = 2.

[edit] Protium

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

1. (working on it)


<@ LETVARLIT>Δ|1</@>
<@ SAYVAR>Δ</@>

Using what Google Translate says is the Traditional Chinese for 'delta'

<@ LETVARLIT>三角洲|1</@>
<@ ACTICRVAR>三角洲</@>
<@ SAYVAR>三角洲</@>

[edit] 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.

>>> Δx = 1
>>> Δx += 1
>>> print(Δx)

[edit] R

See ?assign for details.

f <- function(`∆`=1) `∆`+1
[1] 2

[edit] Racket

Racket has virtually no restrictions on valid characters for identifiers. In particular, Unicode identifiers are supported.

#lang racket
;; Racket can use Unicode in identifier names
(define √ sqrt)
(√ 256) ; -> 16
;; and in fact the standard language makes use of some of these
(λ(x) x) ; -> an identity function
;; The required binding:
(define Δ 1)
(set! Δ (add1 Δ))
(printf "Δ = ~s\n" Δ) ; prints "Δ = 2"

[edit] Retro

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

variable Δ
1 !Δ
@Δ putn
1 +Δ
@Δ putn

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

[edit] 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.

  1. Any non-ASCII characters require a magic comment to select the encoding.
  2. 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
# -*- coding: big5 -*-
Δ = 1
Δ += 1
puts Δ
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.|

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
# -*- coding: euc-jp -*-
class Numeric
self <= ♯♭♪
∞ = Float::INFINITY
±5 = [-5, 5]
p [(±5.first.≦ ∞),
(±5.last.≦ ∞),
(∞.≦ ∞)]
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                                       |)].|

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

[edit] Rust

Rust source encoding is specified to be UTF-8. Variable names must begin with a character that has Unicode XID_start property and remaining characters must have the XID_Continue property. (Note that flipping tables is not permitted under current specification)

Non-ASCII identifiers are feature gated since version 0.9

// rustc 0.9 (7613b15 2014-01-08 18:04:43 -0800)
fn main() {
let mut Δ:int = 1;
Δ += 1;
println!("{}", Δ);

[edit] Scala

var Δ = 1
val π = 3.141592
val 你好 = "hello"
Δ += 1

[edit] Sidef

var Δ = 1;
Δ += 1;
say Δ;

[edit] Swift

var Δ = 1
let π = 3.141592
let 你好 = "hello"

[edit] Tcl

Tcl variable names can include any character (the $var syntax can't, but that's just a shorthand for the operationally-equivalent [set var]). Thus, this script is entirely legal:

set Δx 1
incr Δx
puts [set Δx]

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.

It is also possible to encode characters using a \uXXXX substitution (each X is a hexadecimal digit), thus the Δx could be replaced throughout above by \u0394x; the result is a variable with exactly the same name as before. Doing this allows a script to be written with just ASCII characters, which tends to maximize portability across platforms.

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