Function prototype: Difference between revisions
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output = multiply(10,12)
end</lang>
=={{header|Wren}}==
Firstly, Wren makes a distinction between functions and methods. The latter are always members of a class and never need to be prototyped regardless of the order in which they are declared or called.
On the other hand functions are standalone objects and cannot be called before they have been declared. Consequently, prototypes are required if a function calls itself recursively, if two (or more) functions are mutually recursive or if a function is simply called out of order for some reason.
A prototype is just a forward declaration of the function's name. Details of any parameters are not needed and cannot even be optionally specified as parameters are considered to be part of the function's body.
In the following example, the 'factorial' function is recursive and so needs a forward declaration. However, even though the function takes a single argument, no prior information about that is needed or possible. There is an example of mutual recursion protoyping in the [[Mutual_recursion#Wren]] task.
<lang ecmascript>var factorial // forward declaration
factorial = Fn.new { |n| (n <= 1) ? 1 : factorial.call(n-1) * n }
System.print(factorial.call(5))</lang>
{{out}}
<pre>
120
</pre>
=={{header|zkl}}==
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