## digitalmars.D - Re: poll for properties

```Steven Schveighoffer Wrote:

void foo(Box b)
{
if(b.xxx)
b.fill(5);
else
b.yyy;
}

Assuming you have no idea what type Box is, what of the following options
looks most natural for xxx in order to test to see if b has an element in
it?

a) if(b.empty)
b) if(b.empty())
c) if(b.clear)
d) if(b.clear())

=============

a

=============

What would you guess looks most natural for yyy in order to remove all
elements from b?

a) b.empty;
b) b.empty();
c) b.clear;
d) b.clear();

=============

d

=============

Which of the following functions looks incorrect?

void a(Box box)
{
if(box.empty())
box.fill(5);
else
box.clear();
}

void b(Box box)
{
if(box.empty)
box.fill(5);
else
box.clear;
}

void c(Box box)
{
if(box.clear)
box.fill(5);
else
box.empty;
}

void d(Box box)
{
if(box.clear())
box.fill(5);
else
box.empty();
}

==============

All of them. It's impossible to determine which method clears and which checks
for emptyness. I don't like b.yyy; hanging on its own either.

==============

You read the documentation for Box, and it looks like this:

/**
* check to see if a box is clear
*/
bool clear();

/**
* empty a box, returning true if the box had contents before emptying
*/
bool empty();

Now knowing what the actual meaning of clear and empty are, indicate which
version(s) of the function in the previous question would surprise you if
it compiled.

Here are the functions again for reference:

void a(Box box)
{
if(box.empty())
box.fill(5);
else
box.clear();
}

void b(Box box)
{
if(box.empty)
box.fill(5);
else
box.clear;
}

void c(Box box)
{
if(box.clear)
box.fill(5);
else
box.empty;
}

void d(Box box)
{
if(box.clear())
box.fill(5);
else
box.empty();
}

==============

Did you mean, which function's behavior would surprise me in run time? Given
the functions' code structure there's only one possible way for meaningful
operation: if clause checks for emtyness, else clause empties. So the first two
functions will surprise.

==============

Do you think the meaning of a symbol with parentheses suggests something
different than that same symbol without parentheses for the following
symbols:

a) select
b) rock
c) keyboard
d) elevate