3 Production expressions🔗ℹ

A production expression is a pattern of symbols and tokens in a grammar. Production expressions are used by production rules to describe what pattern of tokens a symbol corresponds to. Production expressions come in a few variants:

• A group expression matches a group of subexpressions in series.

• A choice expression tries subexpressions one at a time and selects the first matching subexpression.

• A repetition expression matches a single subexpression multiple times in series.

• A cut expression matches a subexpression but omits the match from the parse tree.

• A terminal symbol, which matches a single token in the input stream.

• A nonterminal symbol, which refers to other production expressions as defined by the production rules of the grammar.

procedure (atom-symbol? v) → boolean?

v : any/c

procedure (atom-symbol type) → atom-symbol?

type : symbol?

procedure (punctuation-symbol? v) → boolean?

v : any/c

procedure (punctuation-symbol str) → punctuation-symbol?

str : string?

procedure (nonterminal-symbol? v) → boolean?

v : any/c

procedure (nonterminal-symbol key) → nonterminal-symbol?

key : any/c