360 lines
13 KiB
Racket
360 lines
13 KiB
Racket
#lang racket/base
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(require (for-syntax racket/base
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racket/set
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racket/syntax
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racket/match
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racket/private/sc
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unstable/struct)
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racket/match
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racket/vector
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syntax/stx
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syntax/parse/private/residual
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unstable/struct)
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(provide template
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??
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?@)
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#|
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To do:
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- improve error messages
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- support flexible depths, eg
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(with-syntax ([(a ...) #'(1 2 3)]
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[((b ...) ...) #'((1 2 3) (4 5 6) (7 8 9))])
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#'(((a b) ...) ...)) ;; a has depth 1, used at depth 2
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|#
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#|
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A Template (T) is one of:
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- pvar
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- atom (including (), not pvar)
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- (H . T)
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- (H ... . T), (H ... ... . T), etc
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- (?? T T)
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- ... other standard compound forms
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A HeadTemplate (H) is one of:
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- T
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- (?? T)
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- (?@ . T)
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|#
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(define-syntax (template stx)
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(parameterize ((current-syntax-context stx))
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(syntax-case stx ()
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[(template t)
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(let-values ([(guide pvars) (parse-template #'t)])
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;; (eprintf "guide = ~s\n" guide)
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(with-syntax ([guide
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guide]
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[(var ...)
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(for/list ([pvar (in-vector pvars)])
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(let* ([valvar (syntax-mapping-valvar pvar)]
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[attr (syntax-local-value valvar (lambda () #f))])
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(cond [(attribute-mapping? attr)
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(attribute-mapping-var attr)]
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[else valvar])))])
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(syntax-arm #'(substitute (quote-syntax t) 'guide (vector var ...)))))])))
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(define-syntaxes (?? ?@)
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(let ([tx (lambda (stx) (raise-syntax-error #f "not allowed as an expression" stx))])
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(values tx tx)))
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;; ============================================================
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#|
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A Guide (G) is one of:
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- _
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- (G . G)
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- positive-integer
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- negative-integer
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- #s(stxvector G)
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- #s(stxstruct G)
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- #&G
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- #s(dots HG (vector-of integer) nat G)
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- #s(app HG G)
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- #s(escaped G)
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- #s(orelse G (vector-of integer) G)
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A HeadGuide (HG) is one of:
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- G
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- #s(app-opt G (vector-of integer))
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- #s(splice G)
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|#
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(define-syntax-rule (begin-both-phases form ...)
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(begin (begin-for-syntax form ...)
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(begin form ...)))
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(begin-both-phases
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(struct stxvector (g) #:prefab)
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(struct stxstruct (g) #:prefab)
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(struct dots (head hdrivers nesting tail) #:prefab)
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(struct app (head tail) #:prefab)
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(struct escaped (body) #:prefab)
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(struct orelse (g1 drivers1 g2) #:prefab)
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(struct app-opt (g drivers) #:prefab)
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(struct splice (g) #:prefab))
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;; ============================================================
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(begin-for-syntax
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(define (parse-template t)
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(let-values ([(_const? drivers pre-guide) (parse-t t 0 #f)])
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;; (eprintf "pre-guide = ~s\n" pre-guide)
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(define (pvar-set->env drivers)
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(for/hash ([pvar (in-set drivers)]
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[n (in-naturals 1)])
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(values pvar n)))
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(define main-env (pvar-set->env drivers))
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(define (loop g loop-env)
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(define (pvar->index pvar)
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(let ([loop-index (hash-ref loop-env pvar #f)])
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(if loop-index
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(- loop-index)
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(hash-ref main-env pvar))))
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(match g
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['_ '_]
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[(cons g1 g2) (cons (loop g1 loop-env) (loop g2 loop-env))]
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[(? syntax-pattern-variable? pvar) (pvar->index pvar)]
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[(dots head hdrivers nesting tail)
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(let* ([sub-loop-env (pvar-set->env hdrivers)]
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[sub-loop-vector (index-hash->vector sub-loop-env pvar->index)])
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(dots (loop head sub-loop-env)
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sub-loop-vector
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nesting
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(loop tail loop-env)))]
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[(app head tail)
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(app (loop head loop-env) (loop tail loop-env))]
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[(escaped g1)
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(escaped (loop g1 loop-env))]
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[(orelse g1 drivers1 g2)
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(orelse (loop g1 loop-env)
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(for/vector ([pvar (in-set drivers1)])
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(pvar->index pvar))
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(loop g2 loop-env))]
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[(stxvector g1)
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(stxvector (loop g1 loop-env))]
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[(stxstruct g1)
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(stxstruct (loop g1 loop-env))]
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[(? box?)
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(box (loop (unbox g) loop-env))]
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[(app-opt g1 drivers1)
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(app-opt (loop g1 loop-env)
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(for/vector ([pvar (in-set drivers1)])
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(pvar->index pvar)))]
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[(splice g1)
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(splice (loop g1 loop-env))]
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[else (error 'parse:convert "bad pre-guide: ~e" g)]))
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(define guide (loop pre-guide #hash()))
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(values guide
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(index-hash->vector main-env))))
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;; ----------------------------------------
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(define (parse-t t depth esc?)
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(syntax-case t (?? ?@)
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[id
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(identifier? #'id)
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(cond [(and (not esc?)
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(or (free-identifier=? #'id (quote-syntax ...))
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(free-identifier=? #'id (quote-syntax ??))
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(free-identifier=? #'id (quote-syntax ?@))))
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(wrong-syntax #'id "illegal use")]
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[else
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(let ([pvar (lookup-pvar #'id depth)])
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(cond [pvar (values #f (set pvar) pvar)]
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[else (values #t (set) '_)]))])]
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[atom
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(atom? (syntax-e #'atom))
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(values #t (set) '_)]
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[(head DOTS . tail)
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(and (not esc?)
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(identifier? #'DOTS) (free-identifier=? #'DOTS (quote-syntax ...)))
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(let-values ([(nesting tail)
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(let loop ([nesting 1] [tail #'tail])
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(syntax-case tail ()
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[(DOTS . tail)
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(and (identifier? #'DOTS) (free-identifier=? #'DOTS (quote-syntax ...)))
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(loop (add1 nesting) #'tail)]
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[else (values nesting tail)]))])
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(let-values ([(hconst? hdrivers _hsplice? hguide) (parse-h #'head (+ depth nesting) esc?)]
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[(tconst? tdrivers tguide) (parse-t tail depth esc?)])
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(values #f
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(set-union hdrivers tdrivers)
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(dots hguide hdrivers nesting tguide))))]
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[(DOTS template)
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(and (not esc?)
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(identifier? #'DOTS) (free-identifier=? #'DOTS (quote-syntax ...)))
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(let-values ([(const? drivers guide) (parse-t #'template depth #t)])
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(values #f drivers (escaped guide)))]
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[(?? t1 t2)
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(not esc?)
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(let-values ([(const1? drivers1 guide1) (parse-t #'t1 depth esc?)]
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[(const2? drivers2 guide2) (parse-t #'t2 depth esc?)])
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(values #f
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(set-union drivers1 drivers2)
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(orelse guide1 drivers1 guide2)))]
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[(?? . _)
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(not esc?)
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(wrong-syntax t "bad pattern")]
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[(head . tail)
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(let-values ([(hconst? hdrivers hsplice? hguide) (parse-h #'head depth esc?)]
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[(tconst? tdrivers tguide) (parse-t #'tail depth esc?)])
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(let ([const? (and hconst? tconst?)])
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(values const?
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(set-union hdrivers tdrivers)
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(cond [const? '_]
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[hsplice? (app hguide tguide)]
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[else (cons hguide tguide)]))))]
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[vec
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(vector? (syntax-e #'vec))
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(let-values ([(const? drivers guide) (parse-t (vector->list (syntax-e #'vec)) depth esc?)])
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(values const? drivers (if const? '_ (stxvector guide))))]
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[pstruct
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(prefab-struct-key (syntax-e #'pstruct))
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(let-values ([(const? drivers guide) (parse-t (struct->list (syntax-e #'pstruct)) depth esc?)])
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(values const? drivers (if const? '_ (stxstruct guide))))]
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[#&template
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(let-values ([(const? drivers guide) (parse-t #'template depth esc?)])
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(values const? drivers (if const? '_ (box guide))))]
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[_ (wrong-syntax t "bad pattern")]))
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(define (parse-h h depth esc?)
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(syntax-case h (?? ?@)
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[(?? t)
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(not esc?)
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(let-values ([(const? drivers guide) (parse-t #'t depth esc?)])
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(values #f drivers #t (app-opt guide drivers)))]
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[(?@ . t)
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(not esc?)
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(let-values ([(const? drivers guide) (parse-t #'t depth esc?)])
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(values #f drivers #t (splice guide)))]
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[t
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(let-values ([(const? drivers guide) (parse-t #'t depth esc?)])
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(values const? drivers #f guide))]))
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(define (atom? x)
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(or (null? x)
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(number? x)
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(boolean? x)
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(string? x)
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(bytes? x)
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(keyword? x)
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(regexp? x)
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(char? x)))
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(define (lookup-pvar id depth)
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(let ([v (syntax-local-value id (lambda () #f))])
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(cond [(syntax-pattern-variable? v)
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(unless (or (= (syntax-mapping-depth v) depth)
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(= (syntax-mapping-depth v) 0))
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(wrong-syntax id
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"pattern variable used at wrong ellipsis depth (expected ~s, used at ~s)"
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(syntax-mapping-depth v)
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depth))
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v]
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[else #f])))
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(define (index-hash->vector hash [f values])
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(let ([vec (make-vector (hash-count hash))])
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(for ([(value index) (in-hash hash)])
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(vector-set! vec (sub1 index) (f value)))
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vec))
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)
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;; ============================================================
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(define (substitute stx g main-env)
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;; (eprintf "main-env = ~s\n" main-env)
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(define (get index lenv)
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(cond [(positive? index)
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(vector-ref main-env (sub1 index))]
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[else
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(vector-ref lenv (- -1 index))]))
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(define (loop stx g lenv)
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(match g
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['_ stx]
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[(cons g1 g2)
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(restx stx (cons (loop (stx-car stx) g1 lenv) (loop (stx-cdr stx) g2 lenv)))]
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[(? exact-integer? index)
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(let ([v (get index lenv)])
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(unless (syntax? v)
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(error 'template "syntax pattern variable is not syntax-valued"))
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v)]
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[(dots ghead henv nesting gtail)
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(define head-stx (stx-car stx))
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(define (nestloop lenv* nesting)
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(cond [(zero? nesting)
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(loop-h head-stx ghead lenv*)]
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[else
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(for ([v (in-vector lenv*)])
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(unless v (error 'template "loop variable is not defined")))
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(let ([len0 (length (vector-ref lenv* 0))])
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(for ([v (in-vector lenv*)])
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(unless (= len0 (length v))
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(error 'template "loop variable count mismatch")))
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(let dotsloop ([len0 len0] [lenv* lenv*])
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(if (zero? len0)
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null
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(let ([lenv** (vector-map car lenv*)])
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(cons (nestloop lenv** (sub1 nesting))
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(dotsloop (sub1 len0) (vector-map! cdr lenv*)))))))]))
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(let ([head-results ;; (listof^nesting (listof stx)) -- extra listof for loop-h
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(nestloop (vector-map (lambda (index) (get index lenv)) henv) nesting)]
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[tail-result (loop (stx-drop nesting (stx-cdr stx)) gtail lenv)])
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(restx stx (deep-append head-results nesting tail-result)))]
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[(app ghead gtail)
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(restx stx (append (loop-h (stx-car stx) ghead lenv)
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(loop (stx-cdr stx) gtail lenv)))]
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[(escaped g1)
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(loop (stx-cadr stx) g1 lenv)]
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[(orelse g1 drivers1 g2)
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(if (for/and ([index (in-vector drivers1)]) (get index lenv))
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(loop (stx-cadr stx) g1 lenv)
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(loop (stx-caddr stx) g2 lenv))]
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[(stxvector g1)
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(restx stx (list->vector (loop (vector->list (syntax-e stx)) g1 lenv)))]
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[(stxstruct g1)
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(let ([s (syntax-e stx)])
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(restx stx (apply make-prefab-struct
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(prefab-struct-key s)
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(loop (struct->list s) g1 lenv))))]
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[(box g1)
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(restx stx (box (loop (unbox (syntax-e stx)) g1 lenv)))]))
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(define (loop-h stx hg lenv)
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(match hg
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[(app-opt g1 drivers1)
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(if (for/and ([index (in-vector drivers1)]) (get index lenv))
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(list (loop (stx-cadr stx) g1 lenv))
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null)]
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[(splice g1)
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(let* ([v (loop (stx-cdr stx) g1 lenv)]
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[v* (stx->list v)])
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(unless v*
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(error 'template "not a syntax list: ~e" v))
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v*)]
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[else (list (loop stx hg lenv))]))
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(loop stx g #f))
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(define (stx-cadr x) (stx-car (stx-cdr x)))
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(define (stx-cddr x) (stx-cdr (stx-cdr x)))
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(define (stx-caddr x) (stx-car (stx-cdr (stx-cdr x))))
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(define (stx-drop n x)
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(cond [(zero? n) x]
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[else (stx-drop (sub1 n) (stx-cdr x))]))
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(define (restx basis val)
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(if (syntax? basis)
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(datum->syntax basis val basis basis)
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val))
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;; deep-append : (listof^(nesting+1) A) nat (listof A) -> (listof A)
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;; (Actually, in practice onto is stx, so this is an improper append.)
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(define (deep-append lst nesting onto)
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(cond [(null? lst) onto]
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[(zero? nesting) (append lst onto)]
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[else (deep-append (car lst) (sub1 nesting)
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(deep-append (cdr lst) nesting onto))]))
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