Parse EBNF: Difference between revisions
Added Algol 68
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See [[Parse EBNF/Tests|the tests]].
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=={{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]].
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<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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