I am heavily using SumType (which I like very much). The problem I am having is that is seems to be causing slow compile times (as can be observed by profiling during the compile). The problem seems to be with match (which is extremely convenient to use). I looked at the code and it does the only reasonable thing too do which is to test each handler against each type. The slow compile time makes development slower and less pleasant, so I am thinking of replacing SumType with my own tagged union and writing out the switches by hand. However, I really don't like this idea since it makes the code less readable and more prone to errors. Any suggestions?

On Thursday, 28 October 2021 at 09:02:52 UTC, JG wrote:

Hi, I'm the author of SumType. Thanks for bringing this to my attention. The good news is, I have not put a lot of effort so far into micro-optimizing the compile-time performance of match, so there is almost certainly room for improvement.

If you have an example of the kind of code you are seeing poor compile-time performance for, I'd be happy to use it as a benchmark/profiling target. Any profiling data you've collected would also be helpful.

I've created issues for this on Bugzilla and the sumtype Github repository:

https://issues.dlang.org/show_bug.cgi?id=22447
https://github.com/pbackus/sumtype/issues/76

On Thursday, 28 October 2021 at 13:30:53 UTC, Paul Backus wrote:

Thank you so much for your response (and thanks for the hard work that went into SumType). Here is a rather contrived example which compiles in around 9 seconds on my machine.

import std;

struct A1 {int val; }
struct A2 {int val; }
struct A3 {int val; }
struct A4 {int val; }
struct A5 {int val; }
struct A6 {int val; }
struct A7 {int val; }
struct A8 {int val; }
struct A9 {int val; }
struct A10 {int val; }
struct A11 {int val; }
struct A12 {int val; }
struct A13 {int val; }
struct A14 {int val; }

alias A = SumType!(A1,A2,A3,A4,A5,A6,A7,A8,A9,A10,A11,A12,A13,A14);

T asserter(T)() { assert(0); }

auto op(A1 x, A1 y, A1 z) { return x.val + y.val + z.val; }
auto op(A2 x, A2 y, A2 z) { return x.val + y.val - z.val; }
auto op(A3 x, A3 y, A3 z) { return x.val + y.val * z.val; }
auto op(A4 x, A4 y, A4 z) { return x.val + y.val & z.val; }
auto op(A5 x, A5 y, A5 z) { return x.val - y.val + z.val; }
auto op(A6 x, A6 y, A6 z) { return x.val - y.val - z.val; }
auto op(A7 x, A7 y, A7 z) { return x.val - y.val * z.val; }
auto op(A8 x, A8 y, A8 z) { return x.val - y.val & z.val; }
auto op(A9 x, A9 y, A9 z) { return x.val * y.val + z.val; }
auto op(A10 x, A10 y, A10 z) { return x.val * y.val - z.val; }
auto op(A11 x, A11 y, A11 z) { return x.val * y.val * z.val; }
auto op(A12 x, A12 y, A12 z) { return x.val * y.val & z.val; }
auto op(A13 x, A13 y, A13 z) { return x.val & y.val + z.val; }
auto op(A14 x, A14 y, A14 z) { return x.val & y.val - z.val; }

auto op(A a, A b, A c) {
     return a.match!(
              x=>b.match!(
                y=>c.match!(z=>op(x,y,z),
                            _=>asserter!int),
                _=>asserter!int));

}

auto op2(A a, A b, A c) {
     alias doMatch = match!(
        (x, y, z) => op(x,y,z),
        (_1, _2, _3) => asserter!int
    );
     return doMatch(a, b, c);
}

void main()
{
    A a = A1(12);
    A b = A1(13);
    A c = A1(14);
    assert(op(a,b,c)==39);
    assert(op2(a,b,c)==39);
}