module Regex;

import std.io.*;

int main(args : String[])
{
    foreach (arg <- args)
    {
        /* operator=~(String, String) returns an array of String results for
         * the matches. When there are no explicit parentheses in a pattern,
         * the array returned contains just one string - the entire matched
         * content. If the pattern does not match, an empty array is returned.
         * An empty array evaluations in a boolean context to false, while an
         * array with a nonzero number of arguments evaluations to true.
         * Hence, the =~ operator can be used in an if() statement to see if
         * the string matches a given pattern
         */
        if (arg =~ "/^\d+$/")
        {
            println(arg, " is a number");
        }
        else if (arg =~ "/^0x\d+$/i")
        {
            println(arg, " is a hexadecimal number");
        }
        else
        {
            /* auto declaration of matches to be of type String[] */
            matches ::= arg =~ "/(.)(.)/";
            if (matches)
            {
                println("first character: ", matches[0],
                        "second character: ", matches[1]);
            }
        }
    }

    return 0;
}