Hello all,
I decided to have a go at solving some easy programming puzzles with
D2/Phobos to see how Phobos, especially ranges and std.algorithm, work
out in simple real-world use cases (the puzzle in question is from
hacker.org, by the way).
The following code is a direct translation of a simple problem
description to D (it is horrible from performance point of view, but
that's certainly no issue here).
---
import std.algorithm;
import std.conv;
import std.stdio;
// The original input string is longer, but irrelevant to this post.
enum INPUT = "93752xxx746x27x1754xx90x93xxxxx238x44x75xx087509";
void main() {
uint sum;
auto tmp = INPUT.dup;
size_t i;
while ( i < tmp.length ) {
char c = tmp[ i ];
if ( c == 'x' ) {
tmp = remove( tmp, i );
i -= 2;
} else {
sum += to!uint( [ c ] );
++i;
}
}
writeln( sum );
}
---
Quite contrary to what you would expect, the call to »remove« fails to
compile with the following error messages: »std/algorithm.d(4287):
Error: front(src) is not an lvalue« and »std/algorithm.d(4287): Error:
front(tgt) is not an lvalue«.
I am intentionally posting this to this NG and not to d.…D.learn, since
this is a quite gross violation of the principle of least surprise in my
eyes.
If this isn't a bug, a better error message via a template constraint or
a static assert would be something worth looking at in my opinion, since
one would probably expect this to compile and not to fail within Phobos
code.
David
