On Thursday, 24 July 2014 at 14:39:12 UTC, H. S. Teoh via
Digitalmars-d-learn wrote:
On Thu, Jul 24, 2014 at 01:14:40PM +0000, Darren via
Digitalmars-d-learn wrote:
I have the following code in fac.d (modified from the factorial
examples on RosettaCode):
#!/usr/bin/rdmd
import std.bigint;
pure BigInt factorial(BigInt n) {
static pure BigInt inner(BigInt n, BigInt acc) {
return n == 0 ? acc : inner(n - 1, acc * n);
}
return inner(n, BigInt("1"));
}
void main(string[] args) {
import std.stdio;
BigInt input = args[1];
writeln(factorial(input));
return;
}
It (more or less consistently) on my machine will calculate
'fac
47610', and (more or less consistently) will core dump with a
segfault
on 'fac 47611'.
[...]
You're probably running out of stack space because of your
recursive
function. Write it as a loop instead, and you should be able to
go
farther:
pure BigInt factorial(BigInt n) {
auto result = BigInt(1);
while (n > 1)
result *= n;
return result;
}
T
It does seem that's the case. Which is odd, as I thought that DMD
and LDC did TCO. Not in this case obviously.
PS. This was a slightly silly program, but in the general case,
is there a way to use a core dump to diagnose a stack overflow?
