Initial data commit

Task/Totient-function/Forth/totient-function.fth

@@ -0,0 +1,29 @@
+: totient   \ n -- n' ;
+  DUP DUP 2 ?DO     ( tot n )
+    DUP I DUP * < IF   LEAVE   THEN                     \ for(i=2;i*i<=n;i+=2){
+    DUP I MOD 0= IF					\     if(n%i==0){
+      BEGIN   DUP I /MOD SWAP 0=   WHILE  ( tot n n/i ) \       while(n%i==0);
+        NIP       ( tot n/i )                           \         n/=i;
+      REPEAT
+      DROP                    ( tot n  )  \ Remove the new n on exit from loop
+      SWAP DUP I / - SWAP 	  ( tot' n )        	\       tot-=tot/i;
+    THEN
+  2 I 2 = + +LOOP    \  If I = 2 add 1 else add 2 to loop index.
+  DUP 1 > IF   OVER SWAP / -   ELSE   DROP   THEN ;
+
+: bool.  \ f -- ;
+  IF   ." True "   ELSE   ." False"   THEN ;
+
+: count-primes  \ n -- n' ;
+  0 SWAP 2 ?DO   I DUP totient 1+ = -   LOOP ;
+
+: challenge  \ -- ;
+  CR ."   n   φ    prime" CR
+  26 1 DO
+    I 3 .r
+    I totient DUP 4 .r 4 SPACES
+    1+ I = bool. CR
+  LOOP CR
+  100001 100 DO
+    ." Number of primes up to " I 6 .R ."  is " I count-primes 4 .R CR
+  I 9 * +LOOP  ;