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• Std/io

Read-file-characters-rev

Read an entire file into a character-listp, but in reverse order!

Signature

(read-file-characters-rev filename state) 
  → 
(mv errmsg/contents state)

Arguments

filename — Guard (stringp filename).

This goofy function is just like read-file-characters except that the characters are returned in reverse.

This is faster than read-file-characters because we avoid the cost of reversing the accumulator, and thus require half as many conses.

Note: that we just leave this function enabled. Logically it's just the reverse of read-file-characters.

Definitions and Theorems

Function: read-file-characters-rev

(defun
 read-file-characters-rev
 (filename state)
 (declare (xargs :stobjs (state)))
 (declare (xargs :guard (stringp filename)))
 (let
   ((__function__ 'read-file-characters-rev))
   (declare (ignorable __function__))
   (mbe :logic (b* (((mv contents state)
                     (read-file-characters filename state)))
                   (if (stringp contents)
                       (mv contents state)
                       (mv (rev contents) state)))
        :exec (b* (((mv channel state)
                    (open-input-channel filename
                                        :character state))
                   ((unless channel)
                    (mv (concatenate 'string
                                     "Error opening file " filename)
                        state))
                   ((mv contents state)
                    (tr-read-char$-all channel state nil))
                   (state (close-input-channel channel state)))
                  (mv contents state)))))