Eliminate some spurious consing.

diff --git a/v7/src/runtime/dosdir.scm b/v7/src/runtime/dosdir.scm
index 21ad73f69882f3c3ed67320a68e2b3043dccad00..03d5dd82e48b0535bbe22ff3383630febf1e020f 100644 (file)
--- a/v7/src/runtime/dosdir.scm
+++ b/v7/src/runtime/dosdir.scm
@@ -1,6 +1,6 @@
 #| -*-Scheme-*-
 
-$Header: /Users/cph/tmp/foo/mit-scheme/mit-scheme/v7/src/runtime/dosdir.scm,v 1.2 1992/08/06 13:40:16 jinx Exp $
+$Header: /Users/cph/tmp/foo/mit-scheme/mit-scheme/v7/src/runtime/dosdir.scm,v 1.3 1992/08/06 13:45:41 jinx Exp $
 
 Copyright (c) 1992 Massachusetts Institute of Technology
 
@@ -96,38 +96,35 @@ MIT in each case. |#
           (let* ((len (string-length pattern))
                  (min-len (-1+ len)))
             (cond ((zero? posn)
-                   (let ((suffix (substring pattern 1 len)))
-                     (lambda (instance)
-                       (and (string? instance)
-                            (let ((len* (string-length instance)))
-                              (and (>= len* min-len)
-                                   (string=? suffix
-                                             (substring instance
-                                                        (- len* min-len)
-                                                        len*))))))))
+                   (lambda (instance)
+                     (and (string? instance)
+                          (let ((len* (string-length instance)))
+                            (and (>= len* min-len)
+                                 (substring=?
+                                  pattern 1 len
+                                  instance (- len* min-len) len*))))))
                   ((= posn (-1+ len))
-                   (let ((prefix (substring pattern 0 min-len)))
-                     (lambda (instance)
-                       (and (string? instance)
-                            (let ((len* (string-length instance)))
-                              (and (>= len* min-len)
-                                   (string=? prefix
-                                             (substring instance 0
-                                                        min-len))))))))
+                   (lambda (instance)
+                     (and (string? instance)
+                          (let ((len* (string-length instance)))
+                            (and (>= len* min-len)
+                                 (substring=?
+                                  pattern 0 min-len
+                                  instance 0 min-len))))))
                   (else
-                   (let ((prefix (substring pattern 0 posn))
-                         (suffix (substring pattern (1+ posn) len))
-                         (suffix-len (- len (1+ posn))))
+                   (let* ((suffix-start (1+ posn))
+                          (suffix-len (- len suffix-start)))
                      (lambda (instance)
                        (and (string? instance)
                             (let ((len* (string-length instance)))
-                              (and (>= len* min-len)
-                                   (string=? prefix
-                                             (substring instance 0 posn))
-                                   (string=? suffix
-                                             (substring instance
-                                                        (- len* suffix-len)
-                                                        len*))))))))))))
+                              (and
+                               (>= len* min-len)
+                               (substring=?
+                                pattern 0 posn
+                                instance 0 posn)
+                               (substring=?
+                                pattern suffix-start len
+                                instance (- len* suffix-len) len*)))))))))))
        (else
         (lambda (instance)
           (equal? pattern instance)))))