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; Copyright (c) 1993-2008 by Richard Kelsey. See file COPYING.
(define-record-type base-type :base-type
(really-make-base-type name uid)
base-type?
(name base-type-name)
(uid base-type-uid)) ; an integer
(define-record-discloser :base-type
(lambda (base-type)
(list (base-type-name base-type)
(base-type-uid base-type))))
(define *next-base-type-uid* 0)
(define (next-base-type-uid)
(let ((x *next-base-type-uid*))
(set! *next-base-type-uid* (+ x 1))
x))
(define base-type-table (make-table))
(define (make-base-type name)
(let ((type (really-make-base-type name (next-base-type-uid))))
(table-set! base-type-table name type)
type))
(define (lookup-type id)
(cond ((table-ref base-type-table id)
=> identity)
(else #f)))
(define type/integer (make-base-type 'integer))
(define type/unsigned-integer (make-base-type 'unsigned-integer))
(define type/float (make-base-type 'float))
(define type/null (make-base-type 'null)) ; no value
(define type/unit (make-base-type 'unit)) ; single value
(define type/boolean (make-base-type 'boolean))
(define type/undetermined (make-base-type '?))
(define type/input-port (make-base-type 'input-port))
(define type/output-port (make-base-type 'output-port))
(define type/address (make-base-type 'address))
(define type/char (make-base-type 'char))
(define (make-atomic-type name)
(really-make-base-type name (next-base-type-uid)))
(define type/unknown type/undetermined) ; an alias
(define (type-name type)
(if (base-type? type)
(base-type-name type)
(error "type has no name ~S" type)))
(define (make-base-type-table)
(let ((elts (make-vector *next-base-type-uid* #f)))
(values (lambda (type)
(vector-ref elts (base-type-uid type)))
(lambda (type value)
(vector-set! elts (base-type-uid type) value)))))
;--------------------------------------------------
; This won't terminate on recursive types.
(define (type-eq? type1 type2)
(let ((type1 (maybe-follow-uvar type1))
(type2 (maybe-follow-uvar type2)))
(or (eq? type1 type2)
(and (other-type? type1)
(other-type? type2)
(eq? (other-type-kind type1)
(other-type-kind type2))
(let loop ((l1 (other-type-subtypes type1))
(l2 (other-type-subtypes type2)))
(cond ((null? l1) (null? l2))
((null? l2) #f)
((type-eq? (car l1) (car l2))
(loop (cdr l1) (cdr l2)))
(else #f)))))))
;--------------------------------------------------
; Arrow and pointer types (and perhaps others later)
; All done together to simplify the type walking
(define-record-type other-type :other-type
(really-make-other-type kind subtypes finalized?)
other-type?
(kind other-type-kind)
(subtypes other-type-subtypes set-other-type-subtypes!) ; set when finalized
(finalized? other-type-finalized? set-other-type-finalized?!))
(define (make-other-type kind subtypes)
(really-make-other-type kind subtypes #f))
(define-record-discloser :other-type
(lambda (type)
(case (other-type-kind type)
((arrow)
(list 'arrow-type
(arrow-type-args type)
(arrow-type-result type)))
(else
(cons (other-type-kind type)
(other-type-subtypes type))))))
(define (make-other-type-predicate kind)
(lambda (x)
(and (other-type? x)
(eq? kind (other-type-kind x)))))
; Arrow
(define (make-arrow-type args result)
(make-other-type 'arrow (cons result args)))
(define arrow-type? (make-other-type-predicate 'arrow))
(define (arrow-type-args type)
(cdr (other-type-subtypes type)))
(define (arrow-type-result type)
(car (other-type-subtypes type)))
; Pointer
(define (make-pointer-type type)
(make-other-type 'pointer (list type)))
(define pointer-type? (make-other-type-predicate 'pointer))
(define (pointer-type-to pointer-type)
(car (other-type-subtypes pointer-type)))
(define type/string (make-pointer-type type/char))
; Tuple (used for arguments and returning multiple values)
(define (make-tuple-type types)
(if (and (not (null? types))
(null? (cdr types)))
(car types)
(make-other-type 'tuple types)))
(define tuple-type? (make-other-type-predicate 'tuple))
(define (tuple-type-types type)
(other-type-subtypes type))
;--------------------------------------------------
(define (finalize-type type)
(let ((type (maybe-follow-uvar type)))
(cond ((and (other-type? type)
(not (other-type-finalized? type)))
(let ((subs (other-type-subtypes type)))
(set-other-type-finalized?! type #t)
(set-other-type-subtypes! type (map finalize-type subs))))
((and (uvar? type)
(uvar-tuple-okay? type)) ; unused return value
(bind-uvar! type type/unit)))
type))
;--------------------------------------------------
(define (expand-type-spec spec)
(cond ((pair? spec)
(case (car spec)
((=>)
(make-arrow-type (map expand-type-spec (cadr spec))
(make-tuple-type (map expand-type-spec
(cddr spec)))))
((^)
(make-pointer-type (expand-type-spec (cadr spec))))
((tuple)
(make-tuple-type (map expand-type-spec (cdr spec))))
(else
(error "unknown type syntax ~S" spec))))
((not (symbol? spec))
(error "unknown type syntax ~S" spec))
((lookup-type spec)
=> identity)
((lookup-record-type spec)
=> make-pointer-type)
(else
(error "unknown type name ~S" spec))))
;--------------------------------------------------
(define (display-type type port)
(define (do-list list)
(write-char #\( port)
(cond ((not (null? list))
(do-type (car list))
(for-each (lambda (type)
(write-char #\space port)
(do-type type))
(cdr list))))
(write-char #\) port))
(define (do-type type)
(let ((type (maybe-follow-uvar type)))
(cond ((base-type? type)
(display (base-type-name type) port))
((record-type? type)
(display (record-type-name type) port))
((arrow-type? type)
(write-char #\( port)
(do-list (arrow-type-args type))
(display " -> " port)
(do-type (arrow-type-result type))
(write-char #\) port))
((pointer-type? type)
(write-char #\* port)
(do-type (pointer-type-to type)))
((uvar? type)
(write-char #\T port)
(display (uvar-id type) port))
((type-scheme? type)
(display "(for-all " port)
(do-list (type-scheme-free-uvars type))
(display " " port)
(do-type (type-scheme-type type))
(display ")" port))
((tuple-type? type)
(display "(tuple " port)
(do-list (tuple-type-types type))
(display ")" port))
(else
(bug "don't know how to display type ~S" type)))))
(do-type type))
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