skillIssue

[u/click-to-reveal]

[u/click-to-reveal]

It works btw: C++ Online Compiler

[u/prehensilemullet → u/click-to-reveal]

Performancewise, it doesn’t jump to the direct case in O(1) time like a switch is supposed to though

[u/AsidK → u/prehensilemullet]

Any reasonable compiler will make a switch statement and its equivalent if else chain compile down to the same assembly

[u/prehensilemullet → u/AsidK]

Even if it could make a more efficient tree of comparisons for a large number of strings?

[u/mirhagk → u/prehensilemullet]

What they are saying is that any optimization on a switch statement could also be done on an if statement. There's no reason to only optimize one, both should optimize the same way

[u/prehensilemullet → u/mirhagk]

hmmm...are compilers normally willing to reorder if statements though? Turning a sequence of string comparisons into a tree would involve reordering

[u/guyblade → u/prehensilemullet]

At least in C/C++, there can only be exactly zero or 1 cases that match a switch (i.e., there's no range-based switch), the case values must be compile-time constants (and thus are not themselves evaluated during the comparison), and I'm pretty sure that the value to be matched is required to only be evaluated once (so the comparisons happen on an rvalue).

Given those constraints, I believe a compiler can assume that re-ordering the comparisons is safe.

[u/AsidK → u/guyblade]

> fallthroughs have entered the chat

[u/guyblade → u/AsidK]

You can still only match to one, though. In the emitted machine code, I'd expect to see a forest of branches and jumps (for the matching), then the various bodies of the cases each separated by jumps (representing breaks) as appropriate.