Initial data commit

Task/Additive-primes/Forth/additive-primes.fth

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+: prime? ( n -- ? ) here + c@ 0= ;
+: notprime! ( n -- ) here + 1 swap c! ;
+
+: prime_sieve ( n -- )
+  here over erase
+  0 notprime!
+  1 notprime!
+  2
+  begin
+    2dup dup * >
+  while
+    dup prime? if
+      2dup dup * do
+        i notprime!
+      dup +loop
+    then
+    1+
+  repeat
+  2drop ;
+
+: digit_sum ( u -- u )
+  dup 10 < if exit then
+  10 /mod recurse + ;
+
+: print_additive_primes ( n -- )
+  ." Additive primes less than " dup 1 .r ." :" cr
+  dup prime_sieve
+  0 swap
+  1 do
+    i prime? if
+      i digit_sum prime? if
+        i 3 .r
+        1+ dup 10 mod 0= if cr else space then
+      then
+    then
+  loop
+  cr . ." additive primes found." cr ;
+
+500 print_additive_primes
+bye