[Resolved] What's 'best' idiom for referring to top of stack?

[mflanagan]

What's the 'best' ('approved'?) idiom for referring to the element on top of a stack? I want to leave the element on top of the stack, so I don't want to pop it; I just need to refer to it. Is it 'count()'? Some reserved function? I assume 'current()' is not correct, yes?

$stack = array();
array_push($stack, ...);
...
$topElement = $stack[count($stack)-1];  // or something else?

Thanks.

Michael

[bad76]

Hi,
I think the top element of a stack is called "Head", but maybe wrong.
And $topElement = $stack[count($stack)-1]; sound good.

However, when you push, it returns the new number of elements in the array. So you can do this too:

$stack = array();
$topPos=array_push($stack, ...);
$topElement = $stack[$topPos];

Or you can use end($stack). (end() )

See you

[Shrike]

The top element is the last one you array_push()'d 🙂

What are you trying to do? If I didn't know what was going into the array, I would use count($array)-1

[mflanagan]

You're right--top is the last one pushed. 🙂 As you say later, though, I don't always know what's going on with the array. Routine A gets the array, and doesn't know what routines B, C, and D have done to the array.

I like 'end()' (bad76's suggestion). Any reason not to use that? Might it interfere with array_pop()/array_push()/etc.?

Thanks again.

[bad76]

The only reason I can find is the execution time.
Maybe the end() function is a bit more slow than $stack[count($stack)-1]; because it "advances array's internal pointer to the last element". Depending on implementation of that "advancing" this can mean even N hidden step (next();next();next();next()... etc...). But I don't think it interfere with array_pop()/array_push()/etc...

See you