Help with Regular Expressions (std.regex)

Samir samir at aol.com
Sun Mar 3 18:07:57 UTC 2019


I am belatedly working my way through the 2018 edition of the 
Advent of Code[1] programming challenges using D and am stumped 
on Problem 3[2].  The challenge requires you to parse a set of 
lines in the format:
#99 @ 652,39: 24x23
#100 @ 61,13: 15x24
#101 @ 31,646: 16x28

I would like to store each number (match) as an element in an 
array so that I can refer to them by index.  For example, for the 
first line:

m = [99, 652, 39, 24, 23]
assert(m[0] == 99);
assert(m[1] == 652);
// ...
assert(m[4] == 23);

What is the best way to do this?  (I will worry about converting 
characters to integers later.)

I have the following solution so far based on reading Dmitry 
Olshansky's article on std.regex[3] and the std.regex 
documention[4]:

import std.stdio;
import std.regex;

void main() {
     auto line    = "#99 @ 652,39: 24x23";
     auto pattern = regex(r"\d+");
     auto m       = matchAll(line, pattern);
     writeln(m);
}

which results in:
[["99"], ["652"], ["39"], ["24"], ["23"]]

But this doesn't seem to be an iterable array as changing 
writeln(m) to writeln(m[0]) yields
Error: no [] operator overload for type RegexMatch!string

Changing the line to writeln(m.front[0]) yields
99

but m.front doesn't allow me to access other elements (i.e. 
m.front[1]):
requested submatch number 1 is out of range
----------------
??:? _d_assert_msg [0x4dc27a]
??:? inout pure nothrow @trusted inout(immutable(char)[]) 
std.regex.Captures!(immutable(char)[]).Captures.opIndex!().opIndex(ulong) [0x4d8d57]
??:? _Dmain [0x49ffc8]

I've tried something like
foreach (m; matchAll(line, pattern))
         writeln(m.hit);

which is close but doesn't result in an array.  Do I need to use 
matchFirst?

Thanks in advance.
Samir

[1] https://adventofcode.com/2018
[2] https://adventofcode.com/2018/day/3
[3] https://dlang.org/articles/regular-expression.html
[4] https://dlang.org/phobos/std_regex.html


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