Re: Template specialized functions creating runtime instructions?
On Wednesday, 21 August 2019 at 00:04:37 UTC, H. S. Teoh wrote: On Tue, Aug 20, 2019 at 11:48:04PM +, ads via Digitalmars-d-learn wrote: [...] 2) Deducing the string as you describe would require CTFE (compile-time function evaluation), which usually isn't done unless the result is *required* at compile-time. The typical way to force this to happen is to store the result into an enum: enum myStr = fizzbuzz!...(...); writeln(myStr); Since enums have to be known at compile-time, this forces CTFE evaluation of fizzbuzz, which is probably what you're looking for here. T Thank you for clearing those up. However even if I force CTFE (line 35), it doesn't seem to help much. https://godbolt.org/z/MytoLF
Re: Template specialized functions creating runtime instructions?
On Tuesday, 20 August 2019 at 23:48:04 UTC, ads wrote: https://godbolt.org/z/hWENgc A somewhat similar translation in C++ also creates a lot of runtime instructions https://godbolt.org/z/psyUtq
Template specialized functions creating runtime instructions?
This piece of code creates a fizzbuzz string with template
parameters.
auto fizzbuzz(uint N)() {
string accumulate;
return fizzbuzz!N(accumulate);
}
auto fizzbuzz(uint N)(ref string result) if (N % 3 && N % 5) {
import std.conv : to;
result ~= N.to!string ~ "\n";
return fizzbuzz!(N - 1)(result);
}
auto fizzbuzz(uint N)(ref string result) if (!(N % 15)) {
result ~= "FizzBuzz\n";
return fizzbuzz!(N - 1)(result);
}
auto fizzbuzz(uint N)(ref string result) if (!(N % 3) && N % 5) {
result ~= "Fizz\n";
return fizzbuzz!(N - 1)(result);
}
auto fizzbuzz(uint N)(ref string result) if (!(N % 5) && N % 3) {
result ~= "Buzz\n";
return fizzbuzz!(N - 1)(result);
}
auto fizzbuzz(uint N : 0)(ref string result) {
return result;
}
void main() {
import std.stdio : writeln;
fizzbuzz!50().writeln();
}
https://godbolt.org/z/hWENgc
In the generated assembly, it looks like it is creating a lot of
runtime instructions, contrary to my belief that templated codes
are purely compile-time. I was expecting that the compiler would
deduce the fizzbuzz string until 50 in compile-time and just
print it in the run-time. Why is this not the case?
Can't add a const ubyte to a dynamic array of ubyte?
import std.stdio;
ubyte[] extend(in uint[] arr)
{
ubyte[] result;
foreach (n; arr)
{
if (n < 10)
{
result ~= n;
// source/app.d(10,11): Error: cannot
append type const(uint) to type ubyte[]
}
else
{
import std.conv : to;
foreach (digit; n.to!string)
{
result ~= digit.to!ubyte;
}
}
}
return result;
}
unittest
{
import std.algorithm : equal;
assert(extend([1, 25, 70, 0]).equal([1, 2, 5, 7, 0, 0]));
}
How can I get around this? I want to ensure that the array is not
mutated in the function in the signature too.
