Structures

An ItemKey designates a part of the input that has been successfully parsed as a certain symbol with certain parameters.

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public struct ItemKey<Param> : Hashable where Param : Hashable

Represents a rule of the grammar.

A rule is similar to a rule in a context-free grammar, and has the form

L => R1 ... Rn

where L is the left-hand side of the rule, and R1 ... Rn is the right-hand side of the rule.

Unlike the rules of a context-free grammar though, each of the symbols L, R1, …, Rn carries an input and an output parameter with them. The property eval (in tandem with the property initialEnv) is responsible for computing these parameters along the stages of the parsing process.

Furthermore, the symbol L does not have to be a nonterminal, but can also be a terminal symbol. In this case, the invocation of this rule during parsing spawns a separate parsing process with a grammar identical with the current grammar, except that L is now treated as a nonterminal symbol. This enables a form of scannerless parsing.

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public struct Rule<Param>

The result of parsing a terminal (either via a lexer or via rules).

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public struct Token<Param, Result> : Hashable where Param : Hashable

A TerminalKey is used to distinguish which terminal and input parameter are under consideration.

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public struct TerminalKey<Param> : Hashable where Param : Hashable