On Sunday, 24 August 2025 at 08:35:57 UTC, Per Nordlöw wrote:
Which are the pros and cons of foreach vs static foreach on a
compile time tuple in D in terms of compiler performance and
resource usage? Does static foreach generate more ast
duplications?
Since enum foreach is being deleted and nore properly implimented
(ugh that not why I report bugs; to remove features) I believe in
practice both should be O(n) but there isnt a way to generate a
alias foreach lazily, it will exist in memory so it must allocate
O(n)
I would predict that alias foreach will be 2x slower until your
ram is filled at a point 1/2 the size of static foreach(at which
point a new curve gets introduced) which swap being worse then
ram skyrockets, then shortly after static foreach joins in.
---
```d
#!opend -unittest -main -run app.d
bool isEvenImpl(int I)()=>! I%2;
enum cases=10000;
import std.range;
bool isEven(int i){
switch(i){
static foreach(I;0..cases){
//foreach(I;enumlist!(iota(cases))){
case I: return isEvenImpl!I;
}
default: assert(0);
}}
template Val(int V){
enum Val=V;
}
alias seq(T...)=T;
template enumlist(alias R){
alias enumlist=seq!();
static foreach(e;R){
enumlist=seq!(enumlist,Val!e);
}}
unittest{
import std;
alias A=enumlist!(iota(5));
A.stringof.writeln;
}
unittest{
import std;
7.isEven.writeln;
}
```
static foreach(I;0..cases){ //2.86s
foreach(I;enumlist!(iota(cases))){ //7.30s
Not going to do more tests but I believe you should stick with
static each when possible but im pretty sure they share bigO
details
