Unicode Syntax

Elixir implements Unicode Annex #31 for non-quoted atoms and variables as specified in this document.

Version

The specification in this document is included in Elixir v1.5 and requires OTP 20+. To check the Unicode version of your current Elixir installation, please run String.Unicode.version().

R1. Default Identifiers

Elixir identifiers are identified as:

<Identifier> := <Start> <Continue>* <Ending>?

where <Start> is:

characters derived from the Unicode General Category of uppercase letters, lowercase letters, titlecase letters, modifier letters, other letters, letter numbers, plus Other_ID_Start, minus Pattern_Syntax and Pattern_White_Space code points

In set notation: [[:L:][:Nl:][:Other_ID_Start:]--[:Pattern_Syntax:]--[:Pattern_White_Space:]]

and <Continue> is:

ID_Start characters, plus characters having the Unicode General Category of nonspacing marks, spacing combining marks, decimal number, connector punctuation, plus Other_ID_Continue, minus Pattern_Syntax and Pattern_White_Space code points.

In set notation: [[:ID_Start:][:Mn:][:Mc:][:Nd:][:Pc:][:Other_ID_Continue:]--[:Pattern_Syntax:]--[:Pattern_White_Space:]]

<Ending> is an addition specific to Elixir that includes the codepoints ? (003F) and ! (0021).

Elixir does not implement requirement R1a. It does implement requirement R1b.

Atoms

Atoms in Elixir follow the identifier rule above with the following modifications:

<Start> includes the codepoint _ (005F)
<Continue> includes the codepoint @ (0040)

Variables

Variables in Elixir follow the identifier rule above with the following modifications:

<Start> includes the codepoint _ (005F)
<Start> must not include Lu (letter uppercase) and Lt (letter titlecase) characters
<Continue> includes Lu (letter uppercase) and Lt (letter titlecase) characters

R6. Filtered Normalized Identifiers

Identifiers in Elixir are case sensitive.

Elixir requires all atoms and variables to be in NFC form. Any other form will fail with a relevant error message. Quoted-atoms and variables can, however, be in any form and are not verified by the parser.

In other words, the atom :josé can only be written with the codepoints 006A 006F 0073 00E9. On the other hand, :"josé" may be written as 006A 006F 0073 00E9 or 006A 006F 0073 0065 0301.

Other considerations

It is worth noting that Elixir supports only codepoints \t (0009), \n (000A), \r (000D) and \s (0020) as whitespace and therefore does not follow requirement R3.

Elixir