Circular primes: Difference between revisions

Content added Content deleted

Inline

@@ Line 690: / Line 690: @@
 : prime? ( n -- f )
-    dup 2 <
+    dup 2 < if drop false exit then
-    if drop false
+    dup 2 mod 0= if 2 = exit then
+    dup 3 mod 0= if 3 = exit then
-    else
-        dup 1 and 0=
+    dup 5 mod 0= if 5 = exit then
+    wheel-prime? ;
-        if 2 =
-        else dup 3 mod 0=
-            if 3 =
-            else dup 5 mod 0=
-                if 5 =
-                else wheel-prime?
-                then
-            then
-        then
-    then ;
 : log10^ ( n -- 10^[log n], log n )
@@ Line 709: / Line 700: @@
 0 rot
     begin dup 9 > while
-        swap 1+ swap  rot 10 * -rot  10 /
+        >r  swap 10 *  swap 1+  r> 10 /
     repeat drop ;
@@ Line 716: / Line 707: @@
 : rotate ( n -- n )
     dup log10^ drop /mod swap 10 * + ;
+: prime-rotation? ( p0 p -- f )
+    tuck <= swap prime? and ;
 : circular? ( n -- f )  \ assume n is not a multiple of 2, 3, 5
     dup wheel-prime? invert
     if  drop false exit
-    then dup >r    \ save original value for comparison
+    then dup >r true
-    dup log10 swap begin over 0> while
+    over log10 0 ?do
-        rotate dup r@ < over prime? invert or if
+        swap rotate j over prime-rotation? rot and
-drop rdrop false exit
+    loop nip rdrop ;
-        then swap 1- swap
-    repeat 2drop rdrop true ;
 : .primes
@@ Line 744: / Line 736: @@
 3 5 7 11 13 17 37 79 113 197 199 337 1193 3779 11939 19937 193939 199933
 </pre>
 =={{header|FreeBASIC}}==
 <lang freebasic>#define floor(x) ((x*2.0-0.5)Shr 1)