Re: Better assert without changing built-in assert

[Andrei Alexandrescu]

On 2/16/11 5:04 AM, Jim wrote:

Jens Mueller Wrote:

Hi,

I'm trying to improve the assertions. I tried the following
auto foo(bool var) {
        return tuple(var, "MyMessage");
}

void bar(bool var, string text) {
}

unittest {
        bar(foo(true).expand);
        //assert(foo(true).expand); // won't compile
}

void main() {}

$ dmd -unittest -run file.d
Commenting in the assert it fails with
"Error: expression
tuple(foo(true)._field_field_0,foo(true)._field_field_1) of type (bool,
string) does not have a boolean value"

assert behaves different when expanding tuples. Any explanations?
If one could do the above without writing the expand then it would
suggest a nice way of enhancing the build-in assert, I think.
If one cannot make it work without the .expand another option may be
to overload the built-in assert to handle tuples. This may be related to
http://d.puremagic.com/issues/show_bug.cgi?id=5547
Then one writes e.g.
assert(throws!MyException(expression))
or
assert(pred!("==")(a, b))
What do you think?

Jens

Or like this:


import std.conv;

string cat(T...)(T ts)
{
        string s;
        foreach(t; ts)
         s ~= to!string(t) ~ " ";
        return s;
}


unittest
{
        ...
        assert(a==b, cat(a,b));
}

There's already text in std.conv with the same semantics.

{
   assert(a==b, text(a,b));
}


Andrei