such as a function that implements a function: the string concatenation
A (string, string)

You are so call
A (string);//to be wrong, because obviously, can't is a parameter to it, because I'm stitching your string function, it must need at least two strings can do you meet your function
A (integer variables, the integer variables);//to be wrong, because obviously, can't is a parameter to it, because I'm stitching your string function, it must need at least two strings can achieve the function you want

Function is a process, and the certain state from x - & gt; Y, x is the input, output, y is the x, y here may be a kind of state, but in all digital computer world, the so-called status is just data,
So, this is my individual thinks, in fact a useful function must have the input and output, only some of them are simple parameters and return, some environment variables, global variables, time,
In that process, function is the input x - & gt; Y, then a valid x is a must, of course,
As a parameter, the parameter type told you it need a what kind of input n to perform n - & gt; M a correct, be want process,

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And you this specific question, do you have specific see the function description, I'm not really understand convection also