Mutual recursion: Difference between revisions

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 =={{header|jq}}==
 jq supports mutual recursion but requires functions to be defined before they are used.
-In the present case, this can be accomplished by first defining
+In the present case, this can be accomplished by defining an inner function.
-a function with the desired arity.  He we define F and M as arity-0 filters:
-<lang jq>def F: 0;  # declare required signature
+He we define F and M as arity-0 filters:
-def M: if . == 0 then 0 else . - ((. - 1) | M | F) end;
+<lang jq>
-def F: if . == 0 then 1 else . - ((. - 1) | F | M) end;
+def M:
-</lang>Example:<lang jq>
+  def F: if . == 0 then 1 else . - ((. - 1) | F | M) end;
+  if . == 0 then 0 else . - ((. - 1) | M | F) end;
+def F:
+  if . == 0 then 1 else . - ((. - 1) | F | M) end;</lang>Example:<lang jq>
 [range(0;20) | F],
 [range(0;20) | M]</lang><lang sh>$ jq -n -c -f Mutual_recursion.jq
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 [1,1,2,2,3,3,4,5,5,6,6,7,8,8,9,9,10,11,11,12]
 [0,0,1,2,2,3,4,4,5,6,6,7,7,8,9,9,10,11,11,12]</lang>
 =={{header|Julia}}==
 <lang julia>F(n) = n < 1 ? one(n) : n - M(F(n - 1))