On Wednesday, 3 October 2018 at 11:01:53 UTC, Chris Katko wrote:
I've got this simple task but I'm trying to perfect it as best
I can to learn something in the process.
I have Linux terminal ASCII codes for coloring terminal output.
string red(string) { /* ... */ }
"Hello world".red => "\033[31mHello World\033[0m"
which translates to "[red]Hello World[reset to normal text]".
I have to do some slight trickery so I can chain them. But it
all works fine. __The function is the same__ no matter what
kind of color, bold, etc attribute I want. The only difference
is the tag/prefix string.
So I have a table (or enum):
enum colors{
reset = "\033[0m",
red = "\033[31m",
bold = "\033[1m" //...
}
Absolute perfection would be some way to add a single line to
that enum (or table) and magically get a new function. I add
"blue" with its prefix code to the enum and immediately I can
do:
"hello world".blue
Add yellow = "\033..." and I can do:
"hello world".bold.yellow
It's an interesting problem. Right now, I made a generic
version that accepts the prefix code string directly called
"color()" and red() translates to a call to color with the red
string. blue() does the same. And so on. But it's still plenty
of boiler plate. I do that so I don't have 80+ functions all a
half-page long--which would be a nightmare to verify.
It's surely nothing mission critical. But I wonder if I can
distill this simple problem down further, I may be able to
learn some tricks for later problems.
Thanks.
A combination of static introspection with string mixins does the
trick:
---
enum colors {
reset = "\033[0m",
red = "\033[31m"
}
auto GenerateColorFuncs() {
string result;
static foreach(c; __traits(allMembers, colors))
result ~= "auto "~c~"(string str) { return colors."~c~" ~
str ~ colors.reset; }";
return result;
}
mixin(GenerateColorFuncs());
void main()
{
import std.stdio;
writeln("bla".red);
}
---
Although you might want to replace the string concatenation with
something more performant if used a lot.
