Parse EBNF: Difference between revisions
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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]].
<lang perl6>
# A Raku grammar
grammar EBNF {
rule TOP { ^ <title>? '{' [ <production> ]+ '}' <comment>? $ }
rule production { <name> '=' <expression> <[.;]> }
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token comment { <literal> }
token name { <identifier> <?before \h* '='> }
}
class EBNF::Actions {
method TOP($/) {
say "Syntax Tree:\n", $/; # Dump the syntax tree to STDOUT
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method optional($/) { make $<expression>.ast }
method group($/) { make $<expression>.ast }
}
# An array of test cases
my @tests = (
{
ebnf =>
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term = factor { times factor } .
factor = number | '(' expr ')' .
plus = "+" | "-" .
times = "*" | "/" .
number = digit { digit } .
digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" .
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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;
}
Output:
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