Recursive descent parser: Difference between revisions

Revision as of 12:48, 8 May 2020

Revision as of 18:25, 11 May 2020

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The following [[Extended Backus–Naur Form|EBNF]]-like [[formal grammar|grammar]] (for [[Niklaus Wirth]]'s [[PL/0]] programming language, from ''[[Algorithms + Data Structures = Programs]]'') is in [[LL parser|LL(1)]] form:

<sourcesyntaxhighlight lang="ebnf">

program = block "." .

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| number

| "(" expression ")" .

</syntaxhighlight>

</source>

[[terminal symbol|Terminals]] are expressed in quotes. Each [[nonterminal symbol|nonterminal]] is defined by a rule in the grammar, except for ''ident'' and ''number'', which are assumed to be implicitly defined.

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The implementations of the functions ''nextsym'' and ''error'' are omitted for simplicity.

<sourcesyntaxhighlight lang="c">

typedef enum {ident, number, lparen, rparen, times, slash, plus,

minus, eql, neq, lss, leq, gtr, geq, callsym, beginsym, semicolon,

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expect(period);

}

</syntaxhighlight>

</source>

== Examples ==