Proper way to parse a file and build output - file

Question

I'm trying to learn D and I thought after doing the hello world stuff, I could try something I wanted to do in Java before, where it was a big pain because of the way the Regex API worked: A little template engine.
So, I started with some simple code to read through a file, character by character:
import std.stdio, std.file, std.uni, std.array;
void main(string [] args) {
File f = File("src/res/test.dtl", "r");
bool escape = false;
char [] result;
Appender!(char[]) appender = appender(result);
foreach(c; f.rawRead(new char[f.size])) {
if(c == '\\') {
escape = true;
continue;
}
if(escape) {
escape = false;
// do something special
}
if(c == '#') {
// start of scope
}
appender.put(c);
}
writeln(appender.data());
}
The contents of my file could be something like this:
<h1>#{hello}</h1>
The goal is to replace the #{hello} part with some value passed to the engine.
So, I actually have two questions:
1. Is that a good way to process characters from file in D? I hacked this together after searching through all the imported modules and picking what sounded like it might do the job.
2. Sometimes, I would want to access more than one character (to improve checking for escape-sequences, find a whole scope, etc. Should I slice the array for that? Or are D's regex functions up to that challenge? So far, I only found matchFirst and matchAll methods, but I would like to match, replace and return to that position. How could that be done?

Answer 1

D standard library does not provide what you require. What you need is called "string interpolation", and here is a very nice implementation in D that you can use the way you describe: https://github.com/Abscissa/scriptlike/blob/4350eb745531720764861c82e0c4e689861bb17e/src/scriptlike/core.d#L139
Here is a blog post about this library: https://p0nce.github.io/d-idioms/#String-interpolation-as-a-library