CODEWITHSUNDEEP
versiondcompile-time
porton
porton

Reputation: 5805

Compile-time version comparison in D

I want compile-time (because to be used in static if) comparison of version strings in D.

For example 1.2.12 is greater than 1.2.2. I want to do such comparisons compile-time.

Upvotes: 1

Views: 53

Answers (1)

dhasenan
dhasenan

Reputation: 1228

Write a function that works at runtime. Then call it. Something like:

bool less(string a, string b)
{
  auto ap = a.splitter(".").map!(x => to!int(x));
  auto bp = b.splitter(".").map!(x => to!int(x));
  while (!ap.empty && !bp.empty)
  {
    if (ap.front < bp.front) return true;
    ap.popFront; bp.popFront;
  }
  return ap.empty;
}
static if (less("1.2.12", "1.2.2"))
  pragma(msg, "it's less");
else
  pragma(msg, "it's not less");

You can call normal functions at compile time. This is what in D we call CTFE (compile time function evaluation).

To quote Walter Bright (from my memory) "D has the unique ability to run D code at compile time".

Upvotes: 3

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