Cousin primes: Difference between revisions

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@@ Line 76: / Line 76: @@
 =={{header|ALGOL 68}}==
+{{libheader|ALGOL 68-primes}}
 <lang algol68>BEGIN # find cousin primes - pairs of primes that differ by 4 #
+    # sieve the primes as required by the task #
-    INT max number = 1000;
-    # sieve the primes to max number #
+    PR read "primes.incl.a68" PR
-    [ 1 : max number ]BOOL prime;
+    []BOOL prime = PRIMESIEVE 1000;
-    prime[ 1 ] := FALSE; prime[ 2 ] := TRUE;
-    FOR i FROM 3 BY 2 TO max number DO prime[ i ] := TRUE  OD;
-    FOR i FROM 4 BY 2 TO max number DO prime[ i ] := FALSE OD;
-    FOR i FROM 3 BY 2 TO ENTIER sqrt( max number ) DO
-        IF prime[ i ] THEN
-            FOR s FROM i * i BY i + i TO max number DO prime[ s ] := FALSE OD
-        FI
-    OD;
     # returns text right padded to length, if it is shorter #
     PROC right pad = ( STRING text, INT length )STRING:
@@ Line 97: / Line 90: @@
     # look through the primes for cousins #
     INT p count := 0;
-    FOR i TO max number - 4 DO
+    FOR i TO UPB prime - 4 DO
         IF prime[ i ] THEN
             IF prime[ i + 4 ] THEN