30 lines
1.4 KiB
Go
30 lines
1.4 KiB
Go
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// Package lexer defines interfaces and implementations used by Participle to perform lexing.
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//
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// The primary interfaces are Definition and Lexer. There are two concrete implementations
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// included. The first is one based on Go's text/scanner package. The second is Participle's
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// default stateful/modal lexer.
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//
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// The stateful lexer is based heavily on the approach used by Chroma (and Pygments).
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//
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// It is a state machine defined by a map of rules keyed by state. Each rule
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// is a named regex and optional operation to apply when the rule matches.
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//
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// As a convenience, any Rule starting with a lowercase letter will be elided from output.
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//
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// Lexing starts in the "Root" group. Each rule is matched in order, with the first
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// successful match producing a lexeme. If the matching rule has an associated Action
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// it will be executed. The name of each non-root rule is prefixed with the name
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// of its group to yield the token identifier used during matching.
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//
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// A state change can be introduced with the Action `Push(state)`. `Pop()` will
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// return to the previous state.
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//
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// To reuse rules from another state, use `Include(state)`.
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//
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// As a special case, regexes containing backrefs in the form \N (where N is a digit)
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// will match the corresponding capture group from the immediate parent group. This
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// can be used to parse, among other things, heredocs.
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//
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// See the README, example and tests in this package for details.
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package lexer
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