Data update

Task/Longest-common-substring/REXX/longest-common-substring.rexx

@@ -1,20 +1,53 @@
-/*REXX program determines the   LCSUBSTR   (Longest Common Substring)  via a function.  */
-parse arg a b .                                  /*obtain optional arguments from the CL*/
-if a==''  then a= "thisisatest"                  /*Not specified?  Then use the default.*/
-if b==''  then b= "testing123testing"            /* "      "         "   "     "    "   */
-say '   string A ='            a                 /*echo string A to the terminal screen.*/
-say '   string B ='               b              /*  "     "   B  "  "      "       "   */
-say '   LCsubstr ='   LCsubstr(a, b)             /*display the Longest Common Substring.*/
-exit 0                                           /*stick a fork in it,  we're all done. */
-/*──────────────────────────────────────────────────────────────────────────────────────*/
-LCsubstr: procedure;  parse arg x,y,,$;     #= 0 /*LCsubstr:  Longest Common Substring. */
-          L= length(x);     w= length(y)         /*placeholders for string length of X,Y*/
-          if w<L  then do;  parse arg y,x;  L= w /*switch X & Y   if Y is shorter than X*/
-                       end
-             do j=1  for L  while j<=L-#         /*step through start points in string X*/
-                do k=L-j+1   to #   by -1        /*step through string lengths.         */
-                _= substr(x, j, k)               /*extract a possible common substring. */
-                if pos(_, y)\==0  then  if k>#  then do;     $= _;     #= k;      end
-                end   /*k*/                      /* [↑]  determine if string _ is longer*/
-             end      /*j*/                      /*#:  the current length of  $  string.*/
-          return $                               /*$:  (null if there isn't common str.)*/
+/*REXX program determines the longest Common Substring  via a function.*/
+Parse Arg a b .                 /* obtain arguments from command line  */
+Select
+  When a='?'Then Do             /*Not specified?  prompt for strings   */
+    Say 'Enter two strings'
+    Parse Pull a
+    Parse Pull b
+    End
+  When a='' Then Do             /* else use defaults                   */
+    a='thisisatest'
+    b='testing123testing'
+    End
+  Otherwise
+    Nop
+  End
+cs=LCsubstr(a,b)
+Say '   st A ='||a pax          /*show string A and start position     */
+Say '   st B ='||b pbx          /*  "     "   B  "  "      "       "   */
+Say '   LCtr ='||cs             /*show the Longest Common Substring    */
+Exit
+/*---------------------------------------------------------------------*/
+LCsubstr: Procedure Expose pax pbx /*LCsubstr: Longest Common Substring*/
+  Parse Arg stra,strb,,d        /* get two strings and set d=''        */
+  ll=0                          /* length of common substring so far   */
+  la=length(stra)               /* length of the two strings           */
+  lb=length(strb)
+  switch=0
+  If lb<la Then Do              /* make the shorter string stra        */
+    Parse Arg strb,stra
+    switch=1
+    la=lb
+    End
+  Do pa=1 for la while pa<=la-ll
+    Do k=la-pa+1 to ll By -1
+      ss=substr(stra,pa,k)      /* a substring                         */
+      pb=pos(ss,strb)
+      If pb\==0 Then Do         /* also found in strb                  */
+        If k>ll Then Do         /* longer than one found before        */
+          d=ss                  /* remember the string                 */
+          ll=k                  /* and its length                      */
+          If switch Then        /* note the start positions            */
+            Parse Value pb pa With pax pbx
+          Else
+            Parse Value pa pb With pax pbx
+          End
+        End
+      End
+    End
+  If d='' Then Do
+    d='no common substring found'
+    Parse Value '' With pax pbx
+    End
+  return d