How can I achieve pass-by-reference in Pike?

Question

anyone who can help and is familiar with the Pike language.

I am currently studying the Pike language and I would like to implement a void function that calculates the factorial of a given number "N". The "factorial" function should accept two parameters: the "N" parameter, which represents the calculation limit, and the "RESPONSE" parameter, which will store the calculated factorial value to be returned to the calling program.

I have searched extensively, but I couldn't find any information regarding passing parameters by reference in Pike. It seems like a rather obscure topic or perhaps not widely discussed. I have attempted various parameter passing techniques such as using "*", "&", "ref", "object", "array[][" but unfortunately, none of them worked. I even tried to simulate the pass-by-reference style used in the TCL language, but it also failed to produce the desired result.

If anyone has any insights or suggestions on how to achieve pass-by-reference behavior in Pike, I would greatly appreciate your assistance.

void factorial (int N, ref int FAT) {
  for (int I = 1; I <= N; I++) {
    FAT *= I;
  }
}

Why would you want to return this value in an output parameter rather than as a return value? (BTW, you seem confident that Pike has pass-by-reference, and I don't understand why. Most languages don't, though they typically have other ways of accomplishing any particular thing that you might use pass-by-reference for.) — ruakh, Jul 09 '23 at 06:31
I want to know if Pike supports parameter passing by reference, like C (pointer) and C++ (reference). Additionally, can Lua return multiple results, with some through the return statement and others by reference? Lua can't pass parameters by reference directly, but it allows functions to return multiple results and simulate pass-by-reference behavior using arrays. Does Pike have similar capabilities? — SwFly, Jul 09 '23 at 06:45
I appreciate your interaction. I'm someone who doesn't give up easily, quitting is not an option for me. Not only was I sure about parameter passing by reference in Pike, but I managed to do it because it is inconceivable to me that a language wouldn't offer a way for it to happen. — SwFly, Jul 09 '23 at 07:50
After another 7 hours of research and attempts, I finally discovered it and made the decision to seek help through this channel. Pike doesn't do parameter passing directly like other languages, but it allows it to occur through arrays, which I am providing as the answer to my own post. — SwFly, Jul 09 '23 at 07:51

score 1 · Accepted Answer · edited Jul 09 '23 at 17:39

Pike doesn't have pass-by-reference, but it does have certain reference types that are always implicitly handled via pointers. For example, if a method takes an array parameter, then it actually has a pointer to the same array as the code that calls it, and if it mutates any elements of that shared array, the result will be visible to that calling code. So you can use a single-element array as a sort of de facto pointer, like this:

void fatorial(int N, array(int) FAT) {
    FAT[0] = 1;
    for (int I = 1; I <= N; I++) {
        FAT[0] *= I;
    }
}

int main() {
    array(int) RESP = allocate(1);
    
    RESP[0] = 1;

    factorial(5, RESP);
    write("Factorial = " + RESP[0] + "\n");

    return 0;
}

How can I achieve pass-by-reference in Pike?

1 Answers1