Re: Lazy functions, lazy arrays

[John Colvin via Digitalmars-d-learn]

On Friday, 20 March 2015 at 16:01:51 UTC, Dennis Ritchie wrote:
On Friday, 20 March 2015 at 14:27:06 UTC, John Colvin wrote:
I made a mistake about the static variable and thread-local 
storage.

immutable(int)[] factorials()() @property
{
   static immutable int[N] results = memoizeFactorials(N);
   return results[];
}

is the correct way to do it if you have to.

Still, it's totally not worth doing for such a short array.

Thank you, but I can not figure out how I do this:

import std.stdio;

enum N = 12;

immutable(int)[] factorials()() @property
{
    static immutable int[N] results = memoizeFactorials(N);
    return results[];
}

int[] memoizeFactorials(int n)
{
    if (!__ctfe)
        // Make sure that this function is never called at run 
time
                assert(false);

    int[] result = new int[n];

    result[0] = 1;

    foreach (i; 1 .. n)
        result[i] = result[i - 1] * i;

    return result;
}

void main()
{
        bool flag;
        if (flag) {
                factorials();
                writeln(factorials[10]); // 3628800
        }
        else
                writeln(factorials[10]); // range violation(35)
}

Both of those work for me on multiple dmd versions including git 
HEAD.