50 lines
2.0 KiB
Racket
50 lines
2.0 KiB
Racket
#lang scribble/manual
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@require[scribble/example
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@for-label[auto-syntax-e
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racket/base
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syntax/parse]]
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@title{auto-syntax-e}
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@author{georges}
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@defmodule[auto-syntax-e]
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This package allows using syntax pattern variables outside of syntax
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templates: when @racket[_x] is bound as a syntax pattern variable, writing
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@racket[_x] then becomes roughly equivalent to
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@racket[(syntax->datum #'_x-ddd)], where @racket[_x-ddd] is @racket[x] wrapped
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under the appropriate number of ellipses. If the pattern variable is bound by
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@racket[syntax-parse] and contains non-syntax parts (e.g. it was bound within
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an @racket[~optional] clause, or using @racket[#:attr]), they are left
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unchanged.
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@defform[(auto-with-syntax ([patᵢ eᵢ] ...) body ...)]{
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Like @racket[(with-syntax ([patᵢ eᵢ] ...) body ...)], but the syntax pattern
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variables bound by the @racket[patᵢ ...] can be used outside of syntax patterns
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(they are implicitly transformed using @racket[syntax->datum]):
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@examples[#:eval ((make-eval-factory '(auto-syntax-e)))
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(auto-with-syntax ([x #'123])
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(list (add1 x) #'x))]}
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@defform[(auto-syntax (pvarᵢ ...) body ...)]{
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Re-binds the syntax pattern variables @racket[pvarᵢ ...], so that can be used
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outside of syntax patterns like in @racket[auto-with-syntax]:
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@examples[#:eval ((make-eval-factory '(auto-syntax-e syntax/parse)))
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(syntax-parse #'(1 2 3)
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[(x:nat y:nat ...)
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(auto-syntax (x y)
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(list (map add1 (cons x y)) #'(x y ...)))])
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(syntax-parse #'(1 2 3)
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[({~seq x:nat {~optional y:nat}} ...)
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(auto-syntax (x y)
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(list (map cons x y)
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(attribute x)
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(attribute y)))])]
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When one of the @racket[pvarᵢ ...] is not a syntax pattern variable, it is
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ignored and the existing binding, if any, is left untouched.
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Note that it is not necessary to specify the ellipsis-depth of each
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@racket[pvarᵢ].} |