Add break-lines to unstable/pretty.

collects/unstable/pretty.rkt

@@ -18,3 +18,22 @@
 ;; Ryan: There doesn't seem to be any 'format' going on. Perhaps call
 ;; them pretty-write-to-string, etc?
 ;; Bleh, just saw pretty-format in racket/pretty :(
+
+
+;; by stamourv
+
+(provide break-lines)
+
+;; Takes a string, and breaks it into lines.
+(define (break-lines s [columns (pretty-print-columns)])
+  (define res (open-output-string))
+  (for/fold ([len 0])
+      ([word (in-list (regexp-split #px"[[:blank:]]+" s))])
+    (let ([new-len (+ len (string-length word) 1)])
+      (cond [(< new-len columns)
+             (display (format "~a~a" (if (= len 0) "" " ") word) res)
+             new-len]
+            [else ; break the line
+             (display (format "\n~a" word) res)
+             (string-length word)])))
+  (get-output-string res))

collects/unstable/scribblings/pretty.scrbl

@@ -61,4 +61,15 @@ symmetry with @racket[pretty-format/write] and @racket[pretty-format/display].
 
 }
 
+@addition{@author+email["Vincent St-Amour" "stamourv@racket-lang.org"]}
+@defproc[(break-lines [s string?] [columns exact-nonnegative-integer? (pretty-print-columns)])
+         string?]{
+Splits the string @racket[s] into multiple lines, each of width at most
+@racket[columns], splitting only at whitespace boundaries.
+@examples[#:eval the-eval
+(display (break-lines "This string is more than 80 characters long. It is 98 characters long, nothing more, nothing less."))
+]
+}
+
+
 @(close-eval the-eval)