Detecting Empty Lists

[98b427af]

The isEmpty() function does not distinguish between a list with zero elements and a null variable. What's the best way to tell them apart?

[Martin]

You can check for null:
list == null
or check if list is not null:
list != null

[98b427af]

Thanks!

[98b427af]

A further note on this: isEmpty() returns true for null (undefined) variables, empty strings ("") and empty lists ([]), but *not* for empty maps ({}).

The isEmpty() behavior is thus inconsistent, and there is no way to determine if a map is defined but empty.

[98b427af]

Also, even though you can treat a map as a string in many functions (substring, for example), the test

aMap == "{}"

returns false.

[98b427af]

One more thing:

x = newMap();
matches(x, '\\{\\}')

returns true.

[Martin]

isEmpty does not exist for maps yet so map is converted to a string when the function is called. This is also the case for other method calls. I will add a new isEmpty function specifically for maps.

"{}" is not valid since it will try to evaluate the expression inside the braces and fails. A comparison newMap()=='{}' should work since the curly braces are not interpreted within single quotes.