Hi,
How do you create a type derived from a builtin type such as the array types?
I understand that you can inherit from user-defined types, but the
documentation is conflicting. The "TYPES" file from the ksh source gives an
example involving the special variable ".", which isn't mentioned in the
manpage. The manual only discusses "_" with regards to custom types, but in
addition you're able to set the -a and -A flags when creating instances. I
can't really figure out what this does or why you would do this at the time an
instance is created. Shouldn't there be a base class along the lines of
".sh.type.array" to inherit from in the type definition?
Say for example I wanted to create an object that expands to two words when
referenced. How would you do it? I'm having a difficulty even coming up with
an example that does anything like what I expect.
typeset -T Tuple_t=(
typeset -h 'Declare this as an array type of two members' -a .[2]
integer count # keep track of the current count
function get {
((.sh.value = _.count++))
}
)
Tuple x
for ((i = 0; i++ < 5;)); do
printf '<%s> ' "${x[@]}"
print
done
Expected result:
<0> <1>
<2> <3>
<4> <5>
<6> <7>
<8> <9>
As I understand, the getter should get called once for each element and set
.sh.subscript when requesting multiple values. I've tried hundreds of
permutations on this from creating my own array types to accessing other class
attributes indirectly. Everything produces a surprising result, or just
segfaults.
Also, is there a "call" method for invoking an instance as a function? Is the
only way to interact with objects to assign and dereference values?
--
Dan Douglas
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