avoid being O(n^2) in worst case, improve style

src/julia-parser.scm

@@ -2114,35 +2114,35 @@
 (define (unescape-parsed-string-literal strs)
  (map-at even? unescape-string strs))
 
+;; remove `\` followed by a newline
+(define (strip-escaped-newline s)
+ (let ((in (open-input-string s))
+ (out (open-output-string)))
+ (define (loop preceding-backslash?)
+ (let ((c (read-char in)))
+ (cond ((eof-object? c))
+ (preceding-backslash?
+ (if (not (eqv? c #\newline))
+ (begin (write-char #\\ out) (write-char c out)))
+ (loop #f))
+ ((eqv? c #\\) (loop #t))
+ (else (write-char c out) (loop #f)))))
+ (loop #f)
+ (io.tostring! out)))
+
 (define (parse-string-literal s delim raw)
- (let ((p (ts:port s)))
- ((if raw identity unescape-parsed-string-literal)
- (map (lambda (s)
- (if (and (not raw) (string? s))
- ;; remove `\` followed by a newline
- (let ((spl (string-split s "\\\n")))
- (foldl (lambda (line s)
- ;; if there is an odd number of backslashes before the backslash
- ;; preceding the newline, keep the backslash and newline since
- ;; the backslash is actually escaped
- (define (odd-backslashes? (i (length s)))
- (and (> i 0)
- (let ((i (string.dec s i)))
- (and (eqv? (string.char s i) #\\)
- (not (odd-backslashes? i))))))
- (if (odd-backslashes?)
- (string s "\\\n" line)
- (string s line)))
- ""
- spl))
- s))
- (if (eqv? (peek-char p) delim)
- (if (eqv? (peek-char (take-char p)) delim)
- (map-first strip-leading-newline
- (dedent-triplequoted-string
- (parse-string-literal- 2 (take-char p) s delim raw)))
- (list ""))
- (parse-string-literal- 0 p s delim raw))))))
+ (let* ((p (ts:port s))
+ (str (if (eqv? (peek-char p) delim)
+ (if (eqv? (peek-char (take-char p)) delim)
+ (map-first strip-leading-newline
+ (dedent-triplequoted-string
+ (parse-string-literal- 2 (take-char p) s delim raw)))
+ (list ""))
+ (parse-string-literal- 0 p s delim raw))))
+ (if raw str (unescape-parsed-string-literal
+ (map (lambda (s)
+ (if (string? s) (strip-escaped-newline s) s))
+ str)))))
 
 (define (strip-leading-newline s)
  (let ((n (sizeof s)))