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beautiful-racket/beautiful-racket-demo/basic-demo-2/expander.rkt

49 lines
1.6 KiB
Racket

#lang br/quicklang
(require "struct.rkt"
"elements.rkt")
(provide (rename-out [b-module-begin #%module-begin])
(all-from-out "elements.rkt"))
(define-macro (b-module-begin (b-program LINE ...))
(with-pattern
([((b-line NUM STMT ...) ...) #'(LINE ...)]
[(LINE-FUNC ...) (prefix-id "line-" #'(NUM ...))]
[(VAR-NAME ...) (find-unique-var-names #'(LINE ...))])
#'(#%module-begin
(define VAR-NAME 0) ...
LINE ...
(define line-table
(apply hasheqv (append (list NUM LINE-FUNC) ...)))
(void (run line-table)))))
(begin-for-syntax
(require racket/list)
(define (find-unique-var-names stx)
(remove-duplicates
(for/list ([var-stx (in-list (syntax-flatten stx))]
#:when (syntax-property var-stx 'b-id))
var-stx)
#:key syntax->datum)))
(define (run line-table)
(define line-vec
(list->vector (sort (hash-keys line-table) <)))
(with-handlers ([end-program-signal? (λ (exn-val) (void))])
(for/fold ([line-idx 0])
([i (in-naturals)]
#:break (>= line-idx (vector-length line-vec)))
(define line-num (vector-ref line-vec line-idx))
(define line-func (hash-ref line-table line-num))
(with-handlers
([change-line-signal?
(λ (cls)
(define clsv (change-line-signal-val cls))
(or
(and (exact-positive-integer? clsv)
(vector-member clsv line-vec))
(line-func #:error (format "line ~a not found" clsv))))])
(line-func)
(add1 line-idx)))))