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Parse EBNF (view source)

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See [[Parse EBNF/Tests|the tests]].
<br><br>
 
=={{header|ALGOL 68}}==
 
The source of the Algol 68 sample is somewhat largish, so is on a separate page on Rosetta Code here: [[Parse EBNF/ALGOL 68]].
{{out}}
<pre>
Valid EBNF: a/z: 'a' { a = 'a1' ( 'a2' | 'a3' ) { 'a4' } [ 'a5' ] 'a6' ; } 'z'
a: seq
literal "a1"
oneof
seq
literal "a2"
seq
literal "a3"
list
literal "a4"
opt
literal "a5"
literal "a6"
 
 
"a1a3a4a4a5a6" is valid according to a
 
"a1 a2a6" is valid according to a
 
"a1 a3 a4 a6" is valid according to a
 
**** Syntax error near "a1 a4 a5 a6"
"a1 a4 a5 a6" is not valid according to a
 
**** Syntax error near "a5 a5 a6"
"a1 a2 a4 a5 a5 a6" is not valid according to a
 
**** Unexpected text: "a7" at the end of source
"a1 a2 a4 a5 a6 a7" is not valid according to a
 
**** Syntax error near "your ad here"
"your ad here" is not valid according to a
 
 
Valid EBNF: Arithmetic expressions:
'Arithmetic expressions'
{
expr = term { plus term } .
term = factor { times factor } .
factor = number | '(' expr ')' .
plus = '+' | '-' .
times = '*' | '/' .
number = digit { digit } .
digit = '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' .
}
expr: seq
rule term
list
rule plus
rule term
term: seq
rule factor
list
rule times
rule factor
factor: oneof
seq
rule number
seq
literal "("
rule expr
literal ")"
plus: oneof
seq
literal "+"
seq
literal "-"
times: oneof
seq
literal "*"
seq
literal "/"
number: seq
rule digit
list
rule digit
digit: oneof
seq
literal "0"
seq
literal "1"
seq
literal "2"
seq
literal "3"
seq
literal "4"
seq
literal "5"
seq
literal "6"
seq
literal "7"
seq
literal "8"
seq
literal "9"
 
 
"2" is valid according to Arithmetic expressions
 
"2*3 + 4/23 - 7" is valid according to Arithmetic expressions
 
"(3 + 4) * 6-2+(4*(4))" is valid according to Arithmetic expressions
 
**** Syntax error near "-2"
"-2" is not valid according to Arithmetic expressions
 
**** Unexpected text: "+" at the end of source
"3 +" is not valid according to Arithmetic expressions
 
**** Syntax error near " 3"
"(4 + 3" is not valid according to Arithmetic expressions
 
 
**** Expected "{", not "a"
Invalid EBNF: a = '1';
 
**** Expected "}", not "(eof)"
Invalid EBNF: { a = '1' ;
 
**** Expected "=", not "world"
Invalid EBNF: { hello world = '1'; }
 
**** Rule "bar" not defined
Invalid EBNF: { foo = bar . }
</pre>
 
=={{header|Go}}==
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<br>
A more or less faithful translation except that indices are 0-based rather than 1-based and so 1 less than in the Phix results.
<langsyntaxhighlight lang="go">package main
 
import (
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fmt.Println()
}
}</langsyntaxhighlight>
 
{{out}}
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We use Parsec to generate Parsec.
 
<langsyntaxhighlight lang="haskell">import Control.Applicative
import Control.Monad
import Data.Maybe
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lc c = char c <* ws
 
ws = many $ oneOf " \n\t"</langsyntaxhighlight>
 
=={{header|Julia}}==
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Tested with Julia v1.7.2
 
<langsyntaxhighlight lang="julia">
struct Grammar
regex::Regex
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end
 
</syntaxhighlight>
</lang>
 
 
=={{header|Modula-2}}==
<langsyntaxhighlight lang="modula2">MODULE EBNF;
 
FROM ASCII IMPORT EOL;
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Tabulate (T0);
Tabulate (T1);
END EBNF.</langsyntaxhighlight>
And the source for the EBNF scanner. I hope you like nested procedures.
<langsyntaxhighlight lang="modula2">IMPLEMENTATION MODULE EBNFScanner;
 
FROM ASCII IMPORT LF;
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Ino := 0;
ch := ' '
END EBNFScanner.</langsyntaxhighlight>
 
=={{header|Perl}}==
<langsyntaxhighlight lang="perl">#!/usr/bin/perl
 
use strict; # http://www.rosettacode.org/wiki/Parse_EBNF
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----------------------------------------------------------------------
{ foo = bar . } "undefined production check"
----------------------------------------------------------------------</langsyntaxhighlight>
{{out}}
<pre>
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=={{header|Phix}}==
<!--<langsyntaxhighlight Phixlang="phix">(phixonline)-->
<span style="color: #008080;">with</span> <span style="color: #008080;">javascript_semantics</span>
<span style="color: #004080;">string</span> <span style="color: #000000;">src</span>
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<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
<!--</langsyntaxhighlight>-->
In real use, I would be tempted to use numeric literals rather than string tags in such structures, but the latter certainly make things ten times easier to debug, plus I got an instantly legible syntax tree dump (the bit just after "===>" below) practically for free.
{{out}}
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=={{header|PicoLisp}}==
<langsyntaxhighlight PicoLisplang="picolisp">(de EBNF
"expr : term ( ( PLUS | MINUS ) term )* ;"
"term : factor ( ( MULT | DIV ) factor )* ;"
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(unless (and (match '(@S : @E ;) (str E)) (not (cdr @S)))
(quit "Invalid EBNF" E) )
(put (car @S) 'ebnf @E) ) )</langsyntaxhighlight>
<langsyntaxhighlight PicoLisplang="picolisp">(de matchEbnf (Pat)
(cond
((asoq Pat '((PLUS . +) (MINUS . -) (MULT . *) (DIV . /)))
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(let *Lst (str Str "")
(catch NIL
(parseLst (get 'expr 'ebnf)) ) ) )</langsyntaxhighlight>
Output:
<pre>: (parseEbnf "1 + 2 * -3 / 7 - 3 * 4")
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It is implemented and exercised using the flavor of EBNF and test cases specified on the [[Parse EBNF/Tests|test page]].
 
<syntaxhighlight lang="raku" line># A Raku grammar to parse EBNF
<lang perl6>
# A Raku grammar toEBNF parse EBNF{
rule TOP { ^ <title>? '{' [ <production> ]+ '}' <comment>? $ }
grammar EBNF {
rule rule TOPproduction { ^ <titlename>? '{=' [ <productionexpression> <[.;]+ '}' <comment>? $ }
rule productionexpression { <nameterm> '='+% <expression> <[.;]>"|" }
rule expression term { <termfactor> +% "|" }
rule factor { <group> | <repeat> | <optional> | <identifier> | <literal> }
rule term { <factor>+ }
rule factor { <group> |{ <repeat> |'(' <optionalexpression> | <identifier> | <literal>')' }
rule rule group repeat { '({' <expression> ')}' }
rule rule repeatoptional { '{[' <expression> '}]' }
token identifier { <-[\|\(\)\{\}\[\]\.\;\"\'\s]>+ } #"
rule optional { '[' <expression> ']' }
token identifier literal { ["'" <-[\|\(\)\{\}\[\']\.\;\>+ "\'\s" | '"' <-["]>+ '"'] } #"
token token literal { ["'" <-[']>+ "'"title | '"'{ <-["]literal>+ '"'] } #"
token token titlecomment { <literal> }
token comment name { <literalidentifier> <?before \h* '='> }
}
token name { <identifier> <?before \h* '='> }
 
}
class EBNF::Actions {
class EBNF::Actions {
method TOP($/) {
say "Syntax Tree:\n", $/; # Dump the syntax tree to STDOUT
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">]+\$\}\n " ~ $<production>>>.ast ~ "\}"
}
method production($/) {
make 'token ' ~ $<name> ~ ' {' ~
$<expression>.ast ~ "}\n"
}
method expression($/) { make join '|', $<term>>>.ast }
method term($/) { make join '\h*', $<factor>>>.ast }
method factor($/) {
make $<literal> ?? $<literal> !!
$<group> ?? '[' ~ $<group>.ast ~ ']' !!
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'<' ~ $<identifier> ~ '>'
}
method repeat($/) { make $<expression>.ast }
method optional($/) { make $<expression>.ast }
method group($/) { make $<expression>.ast }
}
 
# An array of test cases
my @tests = (
{
ebnf =>
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teststrings => ['foobar']
}
);
 
# Test the parser.
my $i = 1;
for @tests -> $test {
unless EBNF.parse($test<ebnf>) {
say "Parsing EBNF grammar:\n";
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say '*' x 79, "\n";
unlink $fn;
}</syntaxhighlight>
}
</lang>
 
Output:
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{{in progress|lang=Ruby|day=12|month=May|year=2011}}
{{incomplete|Ruby|The tokenizer is here, but the parser is very incomplete.}}
<langsyntaxhighlight lang="ruby">#--
# The tokenizer splits the input into Tokens like "identifier",
# ":", ")*" and so on. This design uses a StringScanner on each line of
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parse
end
</syntaxhighlight>
</lang>
 
=={{header|Tcl}}==
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Demonstration lexer and parser. Note that this parser supports parenthesized expressions, making the grammar recursive.
<langsyntaxhighlight lang="tcl">package require Tcl 8.6
 
# Utilities to make the coroutine easier to use
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}
throw SYNTAX "\"$payload\" at position $index"
}</langsyntaxhighlight>
 
<langsyntaxhighlight lang="tcl"># Demonstration code
puts [parse "1 - 2 - -3 * 4 + 5"]
puts [parse "1 - 2 - -3 * (4 + 5)"]</langsyntaxhighlight>
Output:
<pre>
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{{trans|Phix}}
{{libheader|Wren-fmt}}
{{libheader|Wren-traititerate}}
{{libheader|Wren-str}}
{{libheader|Wren-seq}}
Translated via the Go entry.
<langsyntaxhighlight ecmascriptlang="wren">import "./fmt" for Conv, Fmt
import "./traititerate" for Stepped
import "./str" for Char
import "./seq" for Lst
 
var src = ""
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System.print()
i = i + 1
}</langsyntaxhighlight>
 
{{out}}
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