Re: Precedences of unary minus and dot operators

[inout]

On Friday, 8 November 2013 at 12:49:38 UTC, bearophile wrote:
This is something that has come out of a thread I have opened 
in D.learn.

In the thread qznc has answered me:

Operator precedence of "." is higher than unary minus.


That's right:


double foo(in double x) {
    assert (x >= 0);
    return x;
}
void main() {
    assert(-1.foo == -1);
}


Is this a good design of the operator precedences? Is this 
worth changing/fixing?

Bye,
bearophile

struct Foo
{
    int value = 9;
};

struct Bar
{
    // implements unary minus
    int value = 9;
};

int squareRoot(Bar bar) { return sqrt(bar.value); }

int main() {
  Foo foo;
  writeln(-foo.value); // prints -9, by first getting the value 
and then negating it

  Bar bar;
  writeln(-bar.squareRoot); // for consistency, this should also 
call squareRoot first
  // otherwise, the order of operations would depend on whether 
the struct has opUnary implemented