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16 lines
415 B
Racket
16 lines
415 B
Racket
#lang brag
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top : (/NEWLINE+ [line])* /NEWLINE*
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line : [lookbehind] pat [lookahead]
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pat : repeat+ | choice
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lookbehind : /"(" /"?" /"<" /"=" pat /")"
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lookahead : /"(" /"?" /"=" pat /")"
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choice : pat (/"|" pat)+
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repeat : repeatable [("*" | "+") ["?"] | "?"]
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@repeatable : group | any | start | end | literal | chars
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group : /"(" pat /")"
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any : /"."
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start : /"^"
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end : /"$"
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literal : LITERAL
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chars : /"[" literal* /"]" |