On 28.03.2011 16:54, simendsjo wrote:
When running compose with two arguments, the implementation uses the
template parameter E. I don't understand what's going on here as E isn't
submitted to the template - what type is E?
I've also seen this in unary/binaryFun using ElementType.
template compose(fun...) { alias composeImpl!(fun).doIt compose; }
// Implementation of compose
template composeImpl(fun...)
{
static if (fun.length == 1)
{
static if (is(typeof(fun[0]) : string))
alias unaryFun!(fun[0]) doIt;
else
alias fun[0] doIt;
}
else static if (fun.length == 2)
{
// starch
static if (is(typeof(fun[0]) : string))
alias unaryFun!(fun[0]) fun0;
else
alias fun[0] fun0;
static if (is(typeof(fun[1]) : string))
alias unaryFun!(fun[1]) fun1;
else
alias fun[1] fun1;
// protein: the core composition operation
typeof({ E a; return fun0(fun1(a)); }()) doIt(E)(E a)
{
return fun0(fun1(a));
}
}
else
{
// protein: assembling operations
alias composeImpl!(fun[0], composeImpl!(fun[1 .. $]).doIt).doIt doIt;
}
}
I think I get it.
doIt becomes the function being called. So E is the type of the
parameter being used when calling compose.
