Initial data commit

Task/Burrows-Wheeler-transform/Zkl/burrows-wheeler-transform-1.zkl

@@ -0,0 +1,17 @@
+class BurrowsWheelerTransform{
+   fcn init(chr="$"){ var special=chr; }
+   fcn encode(str){
+      _assert_(not str.holds(special), "String cannot contain char \"%s\"".fmt(special) );
+      str=str.append(special);
+      str.len().pump(List().merge,'wrap(n){ String(str[n,*],str[0,n]) })
+      .pump(String,T("get",-1));	// last char of each "permutation"
+   }
+   fcn decode(str){
+      table:=List.createLong(str.len(),"");	// ("",""..), mutable
+      do(str.len()){
+	 foreach n in (str.len()){ table[n]=str[n] + table[n] }
+	 table.sort();
+      }   // --> ("$dogwood","d$dogwoo","dogwood$",...)
+      table.filter1("%s*".fmt(special).glob)[1,*];  // str[0]==$, often first element
+   }
+}

Task/Burrows-Wheeler-transform/Zkl/burrows-wheeler-transform-2.zkl

@@ -0,0 +1,10 @@
+BWT:=BurrowsWheelerTransform();
+//BWT.encode("$"); // --> assert(bbb.zkl:25): String cannot contain char "$"
+
+tests:=T(
+    "banana", "appellee", "dogwood", "TO BE OR NOT TO BE OR WANT TO BE OR NOT?",
+    "SIX.MIXED.PIXIES.SIFT.SIXTY.PIXIE.DUST.BOXES",);
+foreach test in (tests){
+   enc:=BWT.encode(test);
+   println("%s\n  -->%s\n  -->%s".fmt(test,enc,BWT.decode(enc)));
+}