On Thursday, 18 May 2017 at 23:15:46 UTC, ag0aep6g wrote:
On 05/19/2017 12:31 AM, Stefan Koch wrote:
string enumToString(E)(E v)
{
static assert(is(E == enum), "emumToString is only meant
for enums");
mixin ({
string result = "final switch(v) {\n";
foreach(m;[__traits(allMembers, E)])
{
result ~= "\tcase E." ~ m ~ " :\n"
~ "\t\treturn \"" ~ m ~ "\";\n"
~ "\tbreak;\n";
}
return result ~ "}";
} ());
}
I'm sure that can be de-uglified a fair bit without hurting
performance.
1) "final switch(v) {" and the closing brace can be moved out
of the string. This should be completely free.
2) No need for `break` after `return`. Also free.
3) With a static foreach over `__traits(allMembers, E)` you can
get rid of the function literal. Doesn't seem to affect
performance much if at all.
So far:
----
string enumToString(E)(E v)
{
static assert(is(E == enum),
"emumToString is only meant for enums");
final switch (v)
{
foreach(m; __traits(allMembers, E))
{
mixin("case E." ~ m ~ ": return \"" ~ m ~ "\";");
}
}
}
----
4) If EnumMembers is an option, you can get rid of the string
mixin altogether:
----
string enumToString(E)(E v)
{
import std.meta: AliasSeq;
import std.traits: EnumMembers;
static assert(is(E == enum),
"emumToString is only meant for enums");
alias memberNames = AliasSeq!(__traits(allMembers, E));
final switch(v)
{
foreach(i, m; EnumMembers!E)
{
case m: return memberNames[i];
}
}
}
----
That takes a bit longer. May just be the time it takes to parse
the std.* modules. Object size stays the same.
Nice work beatifying the implementation.
Although AliasSeq and EnumMembers are unnecessary.
I incorporated your idea into the following version:
string enumToString(E)(E v)
{
static assert(is(E == enum),
"emumToString is only meant for enums");
switch(v)
{
foreach(m; __traits(allMembers, E))
{
case mixin("E." ~ m) : return m;
}
default :
{
string result = "cast(" ~ E.stringof ~ ")";
uint val = v;
enum headLength = E.stringof.length + "cast()".length;
uint log10Val = (val < 10) ? 0 : (val < 100) ? 1 :
(val < 1000) ? 2 :
(val < 10000) ? 3 : (val < 100000) ? 4 : (val <
1000000) ? 5 :
(val < 10000000) ? 6 : (val < 100000000) ? 7 :
(val < 1000000000) ? 8 : 9;
result.length += log10Val + 1;
for(uint i;i != log10Val + 1;i++)
{
cast(char)result[headLength + log10Val - i] =
cast(char) ('0' + (val % 10));
val /= 10;
}
return cast(string) result;
}
}
}
