asciigoat's core library
https://asciigoat.org/core
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83 lines
1.9 KiB
83 lines
1.9 KiB
// Package lexer provides basic helpers to implement parsers |
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package lexer |
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import "io" |
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// Lexer adds Accept and AcceptAll support to a |
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// [io.RuneScanner] |
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type Lexer struct { |
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io.RuneScanner |
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} |
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// Accept consumes a rune from the source if it meets the condition. |
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// it returns true if the condition was met and false if it wasn't. |
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func (p Lexer) Accept(cond func(rune) bool) bool { |
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return Accept(p, cond) |
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} |
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// AcceptAll consumes runes from the source as long as they meet the |
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// condition. it returns true if the condition was met for at least one rune, |
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// and false if it wasn't. |
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func (p Lexer) AcceptAll(cond func(rune) bool) bool { |
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return AcceptAll(p, cond) |
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} |
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// NewLexer extends a [io.RuneScanner] with Accept()/AcceptAll() |
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// functionality |
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func NewLexer(src io.RuneScanner) *Lexer { |
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if src == nil { |
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return nil |
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} |
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return &Lexer{src} |
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} |
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// StateFn is a State Function of the parser |
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type StateFn func() (StateFn, error) |
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// Run runs a state machine until the state function either |
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// returns nil or an error |
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func Run(fn StateFn) error { |
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var err error |
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for fn != nil && err == nil { |
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fn, err = fn() |
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} |
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return err |
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} |
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// Accept consumes a rune from the source if it meets the condition. |
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// it returns true if the condition was met and false if it wasn't. |
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func Accept(src io.RuneScanner, cond func(r rune) bool) bool { |
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r, _, err := src.ReadRune() |
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switch { |
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case err != nil: |
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return false |
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case cond(r): |
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return true |
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default: |
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_ = src.UnreadRune() |
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return false |
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} |
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} |
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// AcceptAll consumes runes from the source as long as they meet the |
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// condition. it returns true if the condition was met for at least one rune, |
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// and false if it wasn't. |
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func AcceptAll(src io.RuneScanner, cond func(r rune) bool) bool { |
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var accepted bool |
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for { |
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r, _, err := src.ReadRune() |
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switch { |
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case err != nil: |
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return accepted |
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case cond(r): |
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accepted = true |
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default: |
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_ = src.UnreadRune() |
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return accepted |
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} |
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} |
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}
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