Couldn't fit this into 140 chars, so it's not gonna be a Twitter message, but instead a short article here. It turns out I don't quite get "lists" in CFML. Or... I'm just being daft. You decide. And tell me.
I've got this code:
// emptyElements.cfm
l="e";
c="";
l = listappend(l,c);
l = listappend(l,"");
l = listappend(l,"");
writeOutput("[#l#]<br>");
l="";
c="e";
l = listappend(l,c);
l = listappend(l,"");
l = listappend(l,"");
writeOutput("[#l#]<br>");
l="";
c="";
l = listappend(l,c);
l = listappend(l,"");
l = listappend(l,"");
writeOutput("[#l#]<br>");
Here I build three lists:
- one starts with an element, then I append three empty elements to it;
- one starts empty, then I append a populated element, followed by two empty elements;
- the last starts empty, and I append three empty elements to it.
A quick quiz... assuming you understand that - by default - CFML lists do not respect empty elements, what would you expect the output to be here?
I'd expect this:
[e]
[e]
[]
Appending an empty element to a list should not append a delimiter as well, as it's unnecessary: empty elements are ignored by lists.
What I do get is this:
[e,,,]
[e,,]
[]
This makes no sense to me: CF (and, I hasten to add, Railo and Lucee) aren't following their own rules here, are they? If empty elements are actually appended (although they shouldn't be), then the results should be:
[e,,,]
[,e,,]
[,,,]
I start with a value and append three blanks
Or I start with nothing, append an actual element, then two blanks
Or I start with nothing and append three blanks.
Whichever way one spins it, I should have the original and three appended elements.
In reality, I should just have the populated element (either the initial value, or the element), and nothing else.
The ColdFusion docs for
listAppend() contradict themselves here. On one hand they say this:If value = "", returns a copy of the list, unchanged.
But they then go on to demonstrate this:
Statement:
ListAppend('elem1,elem2', '' )
Output:
elem1,elem2,
Comment:
Appended element is empty; delimiter is last character in list; list length is 2.
(also note two things: it's an expression, not a statement; and it doesn't output anything, that's just the value of the expression. But anyway).
Lucee's doc's for
listAppend() are - as is generally the case - neither use nor ornament. They just describe the function signature, and offer no further insight. Not helpful.But this seems such a fundamental f***-up, I'm certain I'm missing something obvious.
What is it??
--
Adam
