158 lines
5.4 KiB
Racket
158 lines
5.4 KiB
Racket
#lang scheme
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(provide define-keywords
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;; (define-keywords (name1:identifier ... spec:expr) ...)
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;; constraint: the first name is the original name
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;; and it is also the name of the field in the class
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function-with-arity expr-with-check except err
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->args
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->kwds-in
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clauses-use-kwd)
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(require
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(for-template "syn-aux-aux.ss"
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scheme
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(rename-in lang/prim (first-order->higher-order f2h))))
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(require (for-syntax syntax/parse))
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(define-syntax (define-keywords stx)
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(syntax-parse stx
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[(define-keywords the-list (kw:identifier ... coerce:expr) ...)
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#'(begin
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(provide kw ...) ...
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(define-syntaxes (kw ...)
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(values (lambda (x)
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(raise-syntax-error 'kw "used out of context" x))
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...))
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...
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(define-for-syntax the-list
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(apply append
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(list
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(let* ([x (list (list #'kw ''kw) ...)]
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[f (caar x)])
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(map (lambda (x)
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(define clause-name (car x))
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(define clause-spec (cadr x))
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(list clause-name f (coerce clause-spec)))
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x))
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...))))]))
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#;
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(define-syntax-rule
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(define-keywords the-list (kw coerce) ...)
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(begin
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(provide kw ...)
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(define-syntax kw
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(lambda (x)
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(raise-syntax-error 'kw "used out of context" x)))
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...
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(define-for-syntax the-list
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(list (list #'kw (coerce ''kw)) ...))))
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#|
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transform the clauses into the initial arguments specification
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for a new expression that instantiates the appropriate class
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ensure that the initial state (state0) is not in the shape of a clause
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ensure that all clauses mention only keywords specified in AllSpec or PartSpec
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move the contracts from AppSpecl and PartSpec to the clauses
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run ->rec? over all used keywords to discover the presence of special clauses
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if anything fails, use the legal keyword to specialize the error message
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|#
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(define (->args tag stx state0 clauses AllSpec PartSpec ->rec? legal)
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(define msg (format "not a legal clause in a ~a description" legal))
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(define Spec (append AllSpec PartSpec))
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(define kwds (map (compose (curry datum->syntax stx) car) Spec))
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(define spec (clauses-use-kwd (syntax->list clauses) ->rec? msg kwds))
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(duplicates? tag spec)
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(not-a-clause tag stx state0 kwds)
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(map (lambda (x)
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(define kw (car x))
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(define-values (key coercion)
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(let loop ([kwds kwds][Spec Spec])
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(if (free-identifier=? (car kwds) kw)
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;; -- the original keyword, which is also the init-field name
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;; -- the coercion that comes with it
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(values (cadar Spec) (caddar Spec))
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(loop (cdr kwds) (cdr Spec)))))
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(list key (coercion (cdr x))))
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spec))
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;; Symbol Syntax Syntax [Listof Kw] -> true
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;; effect: if state0 looks like a clause, raise special error
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(define (not-a-clause tag stx state0 kwds)
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(syntax-case state0 ()
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[(kw . E)
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((->kwds-in kwds) #'kw)
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(raise-syntax-error tag "missing initial state" stx)]
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[_ #t]))
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;; Symbol [Listof kw] -> true
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;; effect: raise syntax error about duplicated clause
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(define (duplicates? tag lox)
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(let duplicates? ([lox lox])
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(cond
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[(empty? lox) false]
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[else
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(let* ([f (caar lox)]
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[id (syntax-e f)]
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[x (memf (lambda (x) (free-identifier=? (car x) f)) (rest lox))])
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(if x
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(raise-syntax-error tag (format "duplicate ~a clause" id) (cdar x))
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(duplicates? (rest lox))))])))
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;; check whether rec? occurs, produce list of keywords
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(define (clauses-use-kwd stx:list ->rec? legal-clause kwds)
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(define kwd-in? (->kwds-in kwds))
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(define double (string-append legal-clause ", ~a has been redefined"))
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(map (lambda (stx)
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(syntax-case stx ()
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[(kw . E) (kwd-in? #'kw) (begin (->rec? #'kw #'E) (cons #'kw stx))]
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[(kw . E)
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(let ([kw (syntax-e #'kw)])
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(if (member kw (map syntax-e kwds))
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(raise-syntax-error #f (format double kw) stx)
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(raise-syntax-error #f legal-clause stx)))]
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[_ (raise-syntax-error #f legal-clause stx)]))
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stx:list))
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;; [Listof SyntaxIdentifier] -> (Syntax -> Boolean)
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(define (->kwds-in kwds)
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(lambda (k)
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(and (identifier? k) (for/or ([n kwds]) (free-identifier=? k n)))))
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(define-syntax (expr-with-check stx)
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(syntax-case stx ()
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[(_ check> msg)
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#`(lambda (tag)
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(lambda (p)
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(syntax-case p ()
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[(_ x) #`(check> #,tag x)]
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[_ (err tag p msg)])))]))
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(define-syntax function-with-arity
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(syntax-rules (except)
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[(_ arity)
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(lambda (tag)
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(lambda (p)
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(syntax-case p ()
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[(_ x) #`(proc> #,tag (f2h x) arity)]
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[_ (err tag p)])))]
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[(_ arity except extra)
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(lambda (tag)
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(lambda (p)
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(syntax-case p ()
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[(_ x) #`(proc> #,tag (f2h x) arity)]
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extra
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[_ (err tag p)])))]))
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(define (err spec p . xtras)
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(raise-syntax-error (cadr spec)
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(if (null? xtras)
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"illegal specification"
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(string-append "illegal specification: " (car xtras)))
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p))
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