method EXISTS-POS
Documentation for method EXISTS-POS assembled from the following types:
language documentation Subscripts
From Subscripts
(Subscripts) method EXISTS-POS
multi method EXISTS-POS (::?CLASS: )
Expected to return a Bool indicating whether or not there is an element at position $index. This is what postcircumfix [ ] calls when invoked like @foo[42]:exists.
What "existence" of an element means, is up to your type.
If you don't implement this, your type will inherit the default implementation from Any, which returns True for 0 and False for any other index - which is probably not what you want. So if checking for element existence cannot be done for your type, add an implementation that fails or dies, to avoid silently doing the wrong thing.
class Range
From Range
(Range) method EXISTS-POS
Defined as
multi method EXISTS-POS(Range: int \pos)multi method EXISTS-POS(Range: Int \pos)
Returns True if pos is greater or equal than zero and lower than self.elems. Returns False otherwise.
say (6..10).EXISTS-POS(2); # OUTPUT: «True»say (6..10).EXISTS-POS(7); # OUTPUT: «False»
role Sequence
From Sequence
(Sequence) method EXISTS-POS
multi method EXISTS-POS(::?CLASS: Int )multi method EXISTS-POS(::?CLASS: int )
Returns a Bool indicating whether there is an element at position $idx in the cached sequence.
role Positional
From Positional
(Positional) method EXISTS-POS
method EXISTS-POS(\position)
Should return a Bool indicating whether the given position actually has a value.