tasks a-s

Task/Run-length-encoding/REXX/run-length-encoding-1.rexx

@@ -0,0 +1,23 @@
+/*REXX program encodes string by using a run-length scheme  (min len=2).*/
+parse arg x                            /*normally, input would be a file*/
+def='WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW'
+if x==''  then x=def                   /*No input?  Then use the default*/
+Lx=length(x)                           /*get the length of the X string.*/
+y=                                     /*Y is the output string (so far)*/
+    do j=1  to Lx                      /*warning!  J  is modified below.*/
+    c=substr(x,j,1)                    /*pick a character, check for err*/
+    if \datatype(c,'m') then do;say "error!: data isn't alphabetic";exit 13; end
+    r=0                                /*R  is NOT the number of chars. */
+
+      do k=j+1  to Lx  while  substr(x,k,1)==c
+      r=r+1                            /*R  is a replication count.     */
+      end   /*k*/
+
+    if r==0  then Y = Y || c           /*C  wan't repeated, just OUT it.*/
+             else Y = Y || r || c      /*add it to the encoded string.  */
+    j=j+r                              /*A bad thing to do, but simple. */
+    end   /*j*/
+
+say '  input=' x
+say 'encoded=' y
+                                       /*stick a fork in it, we're done.*/

Task/Run-length-encoding/REXX/run-length-encoding-2.rexx

@@ -0,0 +1,24 @@
+/*REXX program decodes string by using a run-length scheme  (min len=2).*/
+parse arg x                            /*normally, input would be a file*/
+if x==''  then x='11WB11W2B23WB13W'    /*No input?  Then use the default*/
+Lx=length(x)                           /*get the length of the X string.*/
+y=                                     /*Y is the output string (so far)*/
+    do j=1  to Lx                      /*warning!  J  is modified below.*/
+    c=substr(x,j,1)
+    if \datatype(c,'W') then do        /*a loner char, simply add to OUT*/
+                             y=y || c
+                             iterate
+                             end
+    d=1
+        do k=j+1 to Lx while datatype(substr(x,k,1),'w') /*look for #end*/
+        d=d+1                          /*d is the number of digs so far.*/
+        end   /*k*/
+
+    n=substr(x,j,d)+1                  /*D  is length of encoded number.*/
+    y=y || copies(substr(x,k,1),n)     /*N  is now the number of chars. */
+    j=j+d                              /*A bad thing to do, but simple. */
+    end   /*j*/
+
+say '  input=' x
+say 'decoded=' y
+                                       /*stick a fork in it, we're done.*/