Table lookups - this is pretty definitive
Walter Bright
newshound2 at digitalmars.com
Tue Apr 1 11:35:57 PDT 2014
Try this benchmark comparing various classification schemes:
---------------------------------
import core.stdc.stdlib;
import core.stdc.string;
import std.algorithm;
import std.array;
import std.ascii;
import std.datetime;
import std.range;
import std.stdio;
import std.traits;
bool isIdentifierChar0(ubyte c)
{
return isAlphaNum(c) || c == '_' || c == '$';
}
bool isIdentifierChar1(ubyte c)
{
return ((c >= '0' || c == '$') &&
(c <= '9' || c >= 'A') &&
(c <= 'Z' || c >= 'a' || c == '_') &&
(c <= 'z'));
}
immutable bool[256] tab2;
static this()
{
for (size_t u = 0; u < 0x100; ++u)
{
tab2[u] = isIdentifierChar0(cast(ubyte)u);
}
}
bool isIdentifierChar2(ubyte c)
{
return tab2[c];
}
/*********************************************/
int f0()
{
int x;
for (uint u = 0; u < 0x100; ++u)
{
x += isIdentifierChar0(cast(ubyte)u);
}
return x;
}
int f1()
{
int x;
for (uint u = 0; u < 0x100; ++u)
{
x += isIdentifierChar1(cast(ubyte)u);
}
return x;
}
int f2()
{
int x;
for (uint u = 0; u < 0x100; ++u)
{
x += isIdentifierChar2(cast(ubyte)u);
}
return x;
}
void main()
{
auto r = benchmark!(f0, f1, f2)(10_000);
writefln("Milliseconds %s %s %s", r[0].msecs, r[1].msecs, r[2].msecs);
}
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