Matches any single character.

ℹ️ Equivalent regular expression: .

import Parser exposing (parse)


-- We can match any character.
parse "abc" anyChar --> Ok 'a'
parse "#hashtag" anyChar --> Ok '#'


-- This can only fail if we run out of inputs.
import Parser.Error


anyChar
    |> parse ""
    |> Result.mapError Parser.Error.message
--> Err "1:0: I was expecting a character. I reached the end of the input text."

Matches a specific single character. This is case sensitive.

import Parser exposing (parse)


-- Match a specific character, case sensitive.
parse "abc" (char 'a') --> Ok 'a'


-- It fails if it's not _exactly_ the same.
import Parser.Error


char 'a'
    |> parse "ABC"
    |> Result.mapError Parser.Error.message
--> Err "1:1: I was expecting the character 'a'. I got stuck when I got the character 'A'."

Matches a specific single character. This is case insensitive.

import Parser exposing (parse)


-- Match a specific character, case insensitive.
parse "abc" (charNoCase 'a') --> Ok 'a'
parse "ABC" (charNoCase 'a') --> Ok 'A'


-- But anything else makes it fail.
import Parser.Error


charNoCase 'a'
    |> parse "123"
    |> Result.mapError Parser.Error.message
--> Err "1:1: I was expecting the character 'a' (case insensitive). I got stuck when I got the character '1'."

Matches exactly one digit character.

ℹ️ Equivalent regular expression: [0-9] or \d

import Parser exposing (parse)


-- Match a digit.
parse "123" digit --> Ok '1'
parse "3.14" digit --> Ok '3'


-- But anything else makes it fail.
import Parser.Error


digit
    |> parse "abc"
    |> Result.mapError Parser.Error.message
--> Err "1:1: I was expecting a digit [0-9]. I got stuck when I got the character 'a'."

Matches exactly one letter character. This is case insensitive.

ℹ️ Equivalent regular expression: [a-zA-Z]

import Parser exposing (parse)


-- Match any letter, case insensitive.
parse "abc" letter --> Ok 'a'
parse "ABC" letter --> Ok 'A'


-- But anything else makes it fail.
import Parser.Error


letter
    |> parse "123"
    |> Result.mapError Parser.Error.message
--> Err "1:1: I was expecting a letter [a-zA-Z]. I got stuck when I got the character '1'."

Matches exactly one lowercase letter character. This is case sensitive.

ℹ️ Equivalent regular expression: [a-z]

import Parser exposing (parse)


-- Match a lowercase letter.
parse "abc" lowercase --> Ok 'a'


-- But anything else makes it fail.
import Parser.Error


lowercase
    |> parse "ABC"
    |> Result.mapError Parser.Error.message
--> Err "1:1: I was expecting a lowercase letter [a-z]. I got stuck when I got the character 'A'."

Matches exactly one uppercase letter character. This is case sensitive.

ℹ️ Equivalent regular expression: [A-Z]

import Parser exposing (parse)


-- Match an uppercase letter.
parse "ABC" uppercase --> Ok 'A'


-- But anything else makes it fail.
import Parser.Error


uppercase
    |> parse "abc"
    |> Result.mapError Parser.Error.message
--> Err "1:1: I was expecting an uppercase letter [A-Z]. I got stuck when I got the character 'a'."

Matches exactly one letter or digit character. This is case insensitive.

ℹ️ Equivalent regular expression: [a-zA-Z0-9]

import Parser exposing (parse)


-- Match a letter or number.
parse "abc" alphaNum --> Ok 'a'
parse "ABC" alphaNum --> Ok 'A'
parse "123" alphaNum --> Ok '1'


-- But anything else makes it fail.
import Parser.Error


alphaNum
    |> parse "_abc"
    |> Result.mapError Parser.Error.message
--> Err "1:1: I was expecting a letter or a digit [a-zA-Z0-9]. I got stuck when I got the character '_'."

Matches a Unicode blank space character, including new lines. A blank space can be a regular space ' ', tab '\t', new line '\n', carriage return '\r', or form feed '\f'.

ℹ️ Equivalent regular expression: [ \t\n\r\f] or \s

import Parser exposing (parse)


-- Match a space space.
parse "    abc" space --> Ok ' '
parse "\n\t abc" space --> Ok '\n'


-- But anything else makes it fail.
import Parser.Error


parse "abc" space
    |> Result.mapError Parser.Error.message
--> Err "1:1: I was expecting a blank space or new line. I got stuck when I got the character 'a'."

Matches an ASCII punctuation character. A punctuation character can be any of !, ", #, $, %, &, ', (, ), *, +, ,, -, ., /, :, ;, <, =, >, ?, @, [, ], ^, _, \``,`{,}, or~\.

ℹ️ Equivalent regular expression: [!"#$%&'()*+,-./:;<=>?@[\]^_\\{}~]

import Parser exposing (parse)


-- Match a punctuation character.
parse "#hashtag" punctuation --> Ok '#'
parse "=123" punctuation --> Ok '='


-- But anything else makes it fail.
import Parser.Error


punctuation
    |> parse "abc"
    |> Result.mapError Parser.Error.message
--> Err "1:1: I was expecting a punctuation character. I got stuck when I got the character 'a'."

Matches any character except the parser provided.

ℹ️ It's a good idea to use expecting alongside this function to improve the error messages.

import Parser exposing (parse)
import Parser.Error


-- Anything except a letter is okay.
parse "123" (except letter) --> Ok '1'
parse "-123" (except letter) --> Ok '-'


-- But a letter is not.
except letter
    |> parse "abc"
    |> Result.mapError Parser.Error.message
--> Err "1:1: I was expecting a different character. I got stuck when I got the character 'a'."