Case-insensitive BoyerMooreFinder

[Ralf via Digitalmars-d-learn]

Hi,

I just spend a day with the D programming language and I am very 
excited about being able to write such performant programs in 
such an clear and concise way!

I tried to write a little search tool.
The BoyerMooreFinder docs say that the comparison operator can be 
specified. Unfortunately, this doesn't work in practice:

import std.algorithm;
import std.stdio;

void main(string[] args) {
	writeln("> ", find("Hello World", boyerMooreFinder("World")));
	writeln("> ", find("Hello World", boyerMooreFinder!("toLower(a) 
== toLower(b)")("world")));
	writeln("> ", find("EE Hello World", 
boyerMooreFinder!("toLower(a) == toLower(b)")("worl")));
}

Result:

> World
> World
> 

The problem is here:
https://github.com/D-Programming-Language/phobos/blob/v2.069.1/std/algorithm/searching.d#L280

When it looks letters up in its private lookup tables, it uses 
the original letters, not the lower case ones. To work around 
this, I copied the algorithm class, customized this to use the 
.toLower letter here as well and it works like a charm.

I wondered: Do I miss something here? Calling .toLower() on the 
whole string makes this a lot slower; is there a way to customize 
the algorithm with some mapping for the characters? Is there a 
use case for customizing the predicate only?

Greetings,

Ralf