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Gracefully handle the case where the token stream just contains the END token and an error occurs.

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This commit is contained in:
Danny Yoo 2013-01-11 13:59:18 -07:00
parent f93c620814
commit 69ae77a253
1 changed files with 21 additions and 9 deletions
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30
collects/algol60/cfg-parser.rkt
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@ -744,19 +744,31 @@
val val
(next success-k fail-k max-depth tasks)))] (next success-k fail-k max-depth tasks)))]
[fail-k (lambda (max-depth tasks) [fail-k (lambda (max-depth tasks)
(let ([bad-tok (list-ref tok-list (cond
(min (sub1 (length tok-list)) [(null? tok-list)
max-depth))])
(if error-proc (if error-proc
(error-proc #t (error-proc #t
(tok-orig-name bad-tok) 'no-tokens
(tok-val bad-tok) #f
(tok-start bad-tok) (make-position #f #f #f)
(tok-end bad-tok)) (make-position #f #f #f))
(error (error
'cfg-parse 'cfg-parse
"failed at ~a" "no tokens"))]
(tok-val bad-tok)))))]) [else
(let ([bad-tok (list-ref tok-list
(min (sub1 (length tok-list))
max-depth))])
(if error-proc
(error-proc #t
(tok-orig-name bad-tok)
(tok-val bad-tok)
(tok-start bad-tok)
(tok-end bad-tok))
(error
'cfg-parse
"failed at ~a"
(tok-val bad-tok))))]))])
(#,start tok-list (#,start tok-list
;; we simulate a token at the very beginning with zero width ;; we simulate a token at the very beginning with zero width
;; for use with the position-generating code (*-start-pos, *-end-pos). ;; for use with the position-generating code (*-start-pos, *-end-pos).