Re: Overfflow in Assert error messages
On Thursday, 13 February 2020 at 07:49:13 UTC, Adnan wrote:
However my test fails saying something like:
source/binary_search.d(33): [unittest] 18446744073709551615 != 1
core.exception.AssertError@source/binary_search.d(33):
18446744073709551615 != 1
What's causing this underflow?
It's ulong -1, which is the type idx is of on 64-bit systems. On
32-bit systems it will be uint -1 and say "4294967295 != 0".
indexOf is probably not doing what you think it's doing.
int indexOf(T)(const T[] list, const T key) {
return -1;
}
void main()
{
int[] arr = [ 0 ];
foreach (idx, i; arr)
assert(indexOf(arr, i) == idx); // 18446744073709551615
!= 0
}
Overfflow in Assert error messages
I am debugging my simple binary search (I still am):
module binary_search;
debug {
static import std;
}
int indexOf(T)(const T[] list, const T key) {
ulong lo = 0;
ulong hi = list.length - 1;
while (hi > lo) {
const ulong mid = lo + (hi - lo) / 2;
if (list[mid] > key)
hi = mid - 1;
else if (list[mid] < key)
lo = mid + 1;
else {
std.writeln("Returning ", mid, ""); // says
its returning 0
return cast(int) mid;
}
}
return -1;
}
unittest {
scope (success)
std.writeln("binary_search.indexOf -- ok");
int[] arr;
foreach (i; 0 .. 101)
arr ~= i;
assert(arr.length > 1);
foreach (idx, i; arr)
assert(indexOf(arr, i) == idx);
}
However my test fails saying something like:
source/binary_search.d(33): [unittest] 18446744073709551615 != 1
core.exception.AssertError@source/binary_search.d(33):
18446744073709551615 != 1
What's causing this underflow?
I am using "dflags": ["-checkaction=context"] in my dub
configuration file.
