Data commit

Task/Pernicious-numbers/CLU/pernicious-numbers.clu

@@ -0,0 +1,48 @@
+% The population count of an integer is never going to be
+% higher than the amount of bits in it (max 64)
+% so we can get away with a very simple primality test.
+is_prime = proc (n: int) returns (bool)
+    if n<=2 then return(n=2) end
+    if n//2=0 then return(false) end
+    for i: int in int$from_to_by(n+2, n/2, 2) do
+        if n//i=0 then return(false) end
+    end
+    return(true)
+end is_prime
+
+% Find the population count of a number
+pop_count = proc (n: int) returns (int)
+    c: int := 0
+    while n > 0 do
+        c := c + n // 2
+        n := n / 2
+    end
+    return(c)
+end pop_count
+
+% Is N pernicious?
+pernicious = proc (n: int) returns (bool)
+    return(is_prime(pop_count(n)))
+end pernicious
+
+start_up = proc ()
+    po: stream := stream$primary_output()
+
+    stream$putl(po, "First 25 pernicious numbers: ")
+    n: int := 1
+    seen: int := 0
+    while seen<25 do
+        if pernicious(n) then
+            stream$puts(po, int$unparse(n) || " ")
+            seen := seen + 1
+        end
+        n := n + 1
+    end
+
+    stream$putl(po, "\nPernicious numbers between 888,888,877 and 888,888,888:")
+    for i: int in int$from_to(888888877,888888888) do
+        if pernicious(i) then
+            stream$puts(po, int$unparse(i) || " ")
+        end
+    end
+end start_up