On Wednesday, 20 September 2017 at 19:25:58 UTC, Timon Gehr wrote:
Actually, it is useful enough to have a Wikipedia page:
https://en.wikipedia.org/wiki/Iverson_bracket
Mmmm... "The notation was originally introduced by Kenneth E.
Iverson in his programming language APL".
APL... yeah :) Programmers didn't like it, did they. Anyway, that
seems to be explicit notation, analogous to (cond ? 1 : 0).
Example of a good use:
void floodFill(dchar[][] data,dchar c,int i,int j) {
void dfs(int a, int b) {
if (a<0 || a >= data.length) return;
if (b<0 || b >= data[a].length) return;
if (data[a][b] == c) return;
data[a][b] = c;
foreach(i; 0 .. 4){
dfs(a + (i==0) - (i==1),
b + (i==2) - (i==3));
}
}
dfs(i, j);
}
I don't agree it's a good use. Actually, that seems quite
obfuscated to me. Consider:
foreach (point; [[1, 0], [-1, 0], [0, 1], [0, -1]]) {
dfs(a + point[0], b + point[1]);
}
Finds some random 10 programmers and ask them what's easier to
understand...
Also, in my experience (in C and C++) it is extremely rare for
programmers to use booleans in arithmetic. So even if in some
situation you would have to replace this thing with more verbose
(i == 0 ? 1 : 0), it's no big deal.
OTOH, booleans being numbers is a source of some bugs (just like
other cases of weak typing). Not a ton of bugs, but the utility
of implicit conversion to numbers is so unnoticeable that I'm
sure it's just not worth it.
