How to remove all characters from a string, except the integers?

[Stanislav Blinov]

On Thursday, 3 March 2022 at 12:14:13 UTC, BoQsc wrote:

> I need to check if a string contains integers,
> and if it contains integers, remove all the regular string 
> characters.
> I've looked around and it seems using regex is the only closest 
> solution.

```d
import std.stdio;
import std.algorithm : find, filter;
import std.conv : to;
import std.uni : isNumber;

void main(string[] args){
     if (args.length > 1){
	
         auto filtered = () {
             auto r = args[1].find!isNumber; // check if a string 
contains integers
             return r.length ?
                    r.filter!isNumber.to!string // and if it does, 
keep only integers
                    : args[1];                  // otherwise keep 
original
         } ();

         filtered.writeln;
		
     } else {
         write("Please write an argument.");
     }
}
```