• Gary Willoughby (17/17) Nov 26 2013 Why in the following snippet does foo() not collect the exception
• Gary Willoughby (19/19) Nov 26 2013 Figured it out. When using lazy don't pass as a pointer and call

"Gary Willoughby" <dev nomad.so> writes:

Why in the following snippet does foo() not collect the exception 
correctly? It is always null.

import std.exception;
import std.stdio;

public void foo(A : Exception, B)(lazy B func)
{
	auto exception = collectException(func());
	writefln("%s", exception); // This is always null.
}

void bar()
{
	throw new Exception("This is thrown");
}

void main(string[] args)
{
	foo!(Exception)(&bar);
}

"Gary Willoughby" <dev nomad.so> writes:

Figured it out. When using lazy don't pass as a pointer and call 
at the caller site. The argument is then lazily evaluated by the 
called function and not by the caller. This enables passing 
parameters at the caller site too.

import std.exception;
import std.stdio;

public void foo(A : Exception, B)(lazy B func)
{
	auto exception = collectException(func());
	writefln("%s", exception.msg);
}

void bar()
{
	throw new Exception("This is thrown");
}

void main(string[] args)
{
	foo!(Exception)(bar());
}