On Sunday, 3 March 2019 at 18:07:57 UTC, Samir wrote:
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
Hello, Something like this should work:
import std.array: array;
auto allMatches = matchAll(line, pattern).array;
or // sorry i don't have the regex API in mind
import std.array: array;
import std.alogrithm.iteration : map;
auto allMatches = matchAll(line, pattern).map(a => a.hit).array;
What happened with `writeln` is that it iterates the `matchAll`
results which is an input range, which is lazy. `.array` stores
the results in an array.
