• Vathix (29/29) Dec 30 2003 Why can't we throw exceptions in contracts? In my function's "out" contr...
• Walter (4/7) Jan 02 2004 contract

"Vathix" <vathix dprogramming.com> writes:

Why can't we throw exceptions in contracts? In my function's "out" contract
I threw one and it said:
Throw statements cannot be in contracts
But I can call a function that throws one, and even assert throws one.

I wanted to use an exception so the error has a meaningful text reason, not
just assert at this particular line. Isn't this the reason for exceptions
and the toString() member function? But even if assert did take a message,
sometimes I might still want to throw an exception so I don't need to catch
asserts, just like I might not want a regular assert used for array bounds
checks, etc. There is a workaround, but it defeats the purpose of the
contracts:

int asdf(int i)
{
debug(0)
{
    if(!i) throw new GeneralAsdfException("Meaningful asdf expected.");
}
...
}

instead of:

int asdf(int i)
in
{
    if(!i) throw new GeneralAsdfException("Meaningful asdf expected.");
}
body
{
...
}

"Walter" <walter digitalmars.com> writes:

"Vathix" <vathix dprogramming.com> wrote in message
news:bstdke$283s$1 digitaldaemon.com...
 Why can't we throw exceptions in contracts? In my function's "out"

contract
 I threw one and it said:
 Throw statements cannot be in contracts

I can't think of a good reason why not.