88 lines
3.2 KiB
Racket
88 lines
3.2 KiB
Racket
#lang racket/base
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(require syntax/parse
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;syntax/parse/experimental/eh
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generic-syntax-expanders
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phc-toolkit/untyped
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(for-syntax racket/base
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syntax/parse
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racket/syntax
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phc-toolkit/untyped
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racket/list
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racket/pretty)
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"parameters.rkt")
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(provide define-eh-alternative-mixin
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~seq-no-order
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~no-order
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(expander-out eh-mixin))
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(define-expander-type eh-mixin)
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(define-syntax define-eh-alternative-mixin
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(syntax-parser
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[(_ name ((~literal pattern) pat) ...)
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(let ()
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(define-temp-ids "~a/clause" (pat ...))
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#'(define-eh-mixin-expander name
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(λ (_)
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(quote-syntax (~or pat ...)))))]))
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(define-for-syntax (inline-or stx)
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(syntax-case stx ()
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[(o . rest)
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(and (identifier? #'o) (free-identifier=? #'o #'~or))
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(apply append (stx-map inline-or #'rest))]
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[x (list #'x)]))
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;; TODO: ~seq-no-order should also be a eh-mixin-expander, so that when there
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;; are nested ~seq-no-order, the ~post-fail is caught by the nearest
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;; ~seq-no-order.
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(define-syntax ~seq-no-order
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(pattern-expander
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(λ (stx)
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(syntax-case stx ()
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[(self pat ...)
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((λ (x) #;(pretty-write (syntax->datum x)) x)
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(let ()
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(define counter 0)
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(define (increment-counter)
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(begin0 counter
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(set! counter (add1 counter))))
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;; post-acc gathers some a-patterns which will be added after the
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;; (~seq (~or ) ...)
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(define post-acc '())
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(define (add-to-post! v) (set! post-acc (cons v post-acc)))
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;; post-groups-acc gathers some attributes that have to be grouped
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(define post-groups-acc '())
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(define (add-to-post-groups! . v)
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(set! post-groups-acc (cons v post-groups-acc)))
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;; expand EH alternatives:
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(define alts
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(parameterize ([eh-post-accumulate add-to-post!]
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[eh-post-group add-to-post-groups!]
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[clause-counter increment-counter])
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(inline-or (expand-all-eh-mixin-expanders #'(~or pat ...)))))
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(define post-group-bindings
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(for/list ([group (group-by car
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post-groups-acc
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free-identifier=?)])
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;; each item in `group` is a four-element list:
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;; (list result-id aggregate-function attribute)
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(define/with-syntax name (first (car group))
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#;(syntax-local-introduce
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(datum->syntax #'here
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(first (car group)))))
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(define/with-syntax f (second (car group)))
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#`[name (f . #,(map (λ (i) #`(attribute #,(third i)))
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group))]))
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#`(~delimit-cut
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(~and (~seq (~or . #,alts) (... ...))
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~!
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(~bind #,@post-group-bindings)
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#,@post-acc))))]))))
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(define-syntax ~no-order
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(pattern-expander
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(λ/syntax-case (_ . rest) ()
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#'({~seq-no-order . rest})))) |