249 lines
8.8 KiB
Scheme
249 lines
8.8 KiB
Scheme
#lang scheme/base
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;; owner: ryanc
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(require syntax/kerncase
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syntax/stx
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unstable/struct
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(for-syntax scheme/base
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scheme/private/sc)
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(for-template scheme/base))
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(provide unwrap-syntax
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define-pattern-variable
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define/with-syntax
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with-temporaries
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generate-temporary
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generate-n-temporaries
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current-caught-disappeared-uses
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with-catching-disappeared-uses
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with-disappeared-uses
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syntax-local-value/catch
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record-disappeared-uses
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format-symbol
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format-id
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current-syntax-context
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wrong-syntax
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internal-definition-context-apply
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syntax-local-eval
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with-syntax*
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syntax-map)
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;; Unwrapping syntax
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;; unwrap-syntax : any #:stop-at (any -> boolean) -> any
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(define (unwrap-syntax stx #:stop-at [stop-at (lambda (x) #f)])
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(let loop ([x stx])
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(cond [(stop-at x) x]
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[(syntax? x) (loop (syntax-e x))]
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[(pair? x) (cons (loop (car x)) (loop (cdr x)))]
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[(vector? x) (apply vector-immutable (loop (vector->list x)))]
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[(box? x) (box-immutable (loop (unbox x)))]
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[(prefab-struct-key x)
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=> (lambda (key)
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(apply make-prefab-struct key
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(loop (struct->list x))))]
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[else x])))
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;; Eli: Is there any difference between this (with the default) and
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;; `syntax->datum'? If not, then maybe add the optional (or keyword) to
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;; there instead?
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;; Defining pattern variables
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(define-syntax-rule (define-pattern-variable name expr)
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(begin (define var expr)
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(define-syntax name (make-syntax-mapping '0 (quote-syntax var)))))
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;; Statics and disappeared uses
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(define current-caught-disappeared-uses (make-parameter #f))
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(define-syntax-rule (with-catching-disappeared-uses . body)
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(parameterize ((current-caught-disappeared-uses null))
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(let ([result (let () . body)])
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(values result (current-caught-disappeared-uses)))))
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(define-syntax-rule (with-disappeared-uses stx-expr)
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(let-values ([(stx disappeared-uses)
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(with-catching-disappeared-uses stx-expr)])
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(syntax-property stx
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'disappeared-use
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(append (or (syntax-property stx 'disappeared-use) null)
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disappeared-uses))))
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(define (syntax-local-value/catch id pred)
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(let ([value (syntax-local-value id (lambda () #f))])
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(and (pred value)
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(begin (record-disappeared-uses (list id))
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value))))
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(define (record-disappeared-uses ids)
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(let ([uses (current-caught-disappeared-uses)])
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(when uses
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(current-caught-disappeared-uses (append ids uses)))))
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;; Generating temporaries
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;; with-temporaries
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(define-syntax-rule (with-temporaries (temp-name ...) . body)
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(with-syntax ([(temp-name ...) (generate-temporaries (quote-syntax (temp-name ...)))])
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. body))
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;; Eli: +1 to this, not sure about the next two
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;; generate-temporary : any -> identifier
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(define (generate-temporary [stx 'g])
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(car (generate-temporaries (list stx))))
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;; generate-n-temporaries : exact-nonnegative-integer -> (listof identifier)
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(define (generate-n-temporaries n)
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(generate-temporaries
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(for/list ([i (in-range n)])
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(string->symbol (format "g~sx" i)))))
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;; Symbol Formatting
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(define (format-symbol fmt . args)
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(define (convert x) (->atom x 'format-symbol))
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(check-restricted-format-string 'format-symbol fmt)
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(let ([args (map convert args)])
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(string->symbol (apply format fmt args))))
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(define (format-id lctx
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#:source [src #f]
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#:props [props #f]
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#:cert [cert #f]
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fmt . args)
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(define (convert x) (->atom x 'format-id))
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(check-restricted-format-string 'format-id fmt)
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(let* ([args (map convert args)]
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[str (apply format fmt args)]
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[sym (string->symbol str)])
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(datum->syntax lctx sym src props cert)))
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;; Eli: This looks very *useful*, but I'd like to see it more convenient to
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;; "preserve everything". Maybe add a keyword argument that when #t makes
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;; all the others use values lctx, and when syntax makes the others use that
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;; syntax?
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;; Finally, if you get to add this, then another useful utility in the same
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;; spirit is one that concatenates symbols and/or strings and/or identifiers
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;; into a new identifier. I considered something like that, which expects a
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;; single syntax among its inputs, and will use it for the context etc, or
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;; throw an error if there's more or less than 1.
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#|
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(define (id-append #:source [src #f]
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#:props [props #f]
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#:cert [cert #f]
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. args)
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(define stxs (filter syntax? args))
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(define lctx
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(cond [(and (pair? stxs) (null? (cdr stxs)))
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(car stxs)]
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[(error 'id-append "expected exactly one identifier in arguments: ~e" args)]))
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(define (convert x) (->atom x 'id-append))
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(define sym (string->symbol (apply string-append (map convert args))))
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(datum->syntax lctx sym src props cert))
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;; Eli: Yes, that looks nice (with the same comments as above on the keyword
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;; args). It makes more sense with the restriction on the format string.
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|#
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(define (restricted-format-string? fmt)
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(regexp-match? #rx"^(?:[^~]|~[aAn~%])*$" fmt))
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(define (check-restricted-format-string who fmt)
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(unless (restricted-format-string? fmt)
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(raise-type-error who
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"format string using only ~a placeholders"
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fmt)))
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(define (->atom x err)
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(cond [(string? x) x]
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[(symbol? x) x]
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[(identifier? x) (syntax-e x)]
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[(keyword? x) (keyword->string x)]
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[(number? x) x]
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[(char? x) x]
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[else (raise-type-error err
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"string, symbol, identifier, keyword, character, or number"
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x)]))
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;; Error reporting
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(define current-syntax-context (make-parameter #f))
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(define (wrong-syntax stx #:extra [extras null] format-string . args)
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(unless (or (eq? stx #f) (syntax? stx))
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(raise-type-error 'wrong-syntax "syntax or #f" 0 (list* stx format-string args)))
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(let* ([ctx (current-syntax-context)]
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[blame (and (syntax? ctx) (syntax-property ctx 'report-error-as))])
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(raise-syntax-error (if (symbol? blame) blame #f)
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(apply format format-string args)
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ctx
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stx
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extras)))
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;; Eli: The `report-error-as' thing seems arbitrary to me.
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(define (internal-definition-context-apply intdefs stx)
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(let ([qastx (local-expand #`(quote #,stx) 'expression (list #'quote) intdefs)])
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(with-syntax ([(q astx) qastx]) #'astx)))
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(define (syntax-local-eval stx [intdef0 #f])
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(let* ([name (generate-temporary)]
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[intdefs (syntax-local-make-definition-context intdef0)])
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(syntax-local-bind-syntaxes (list name)
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#`(call-with-values (lambda () #,stx) list)
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intdefs)
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(internal-definition-context-seal intdefs)
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(apply values
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(syntax-local-value (internal-definition-context-apply intdefs name)
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#f intdefs))))
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(define-syntax (define/with-syntax stx)
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(syntax-case stx ()
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[(define/with-syntax pattern rhs)
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(let* ([pvar-env (get-match-vars #'define/with-syntax
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stx
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#'pattern
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'())]
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[depthmap (for/list ([x pvar-env])
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(let loop ([x x] [d 0])
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(if (pair? x)
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(loop (car x) (add1 d))
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(cons x d))))]
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[pvars (map car depthmap)]
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[depths (map cdr depthmap)]
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[mark (make-syntax-introducer)])
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(with-syntax ([(pvar ...) pvars]
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[(depth ...) depths]
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[(valvar ...) (generate-temporaries pvars)])
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#'(begin (define-values (valvar ...)
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(with-syntax ([pattern rhs])
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(values (pvar-value pvar) ...)))
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(define-syntax pvar
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(make-syntax-mapping 'depth (quote-syntax valvar)))
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...)))]))
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;; auxiliary macro
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(define-syntax (pvar-value stx)
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(syntax-case stx ()
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[(_ pvar)
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(identifier? #'pvar)
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(let ([mapping (syntax-local-value #'pvar)])
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(unless (syntax-pattern-variable? mapping)
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(raise-syntax-error #f "not a pattern variable" #'pvar))
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(syntax-mapping-valvar mapping))]))
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(define-syntax (with-syntax* stx)
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(syntax-case stx ()
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[(_ (cl) body ...) #'(with-syntax (cl) body ...)]
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[(_ (cl cls ...) body ...)
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#'(with-syntax (cl) (with-syntax* (cls ...) body ...))]))
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(define (syntax-map f . stxls)
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(apply map f (map syntax->list stxls)))
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