Hello,
The code assumes a 'push' with effect ( vec obj -- vec ). Also, this subset
doesn't preserve the type of the input sequence. This is trivial to add and I
think there's a better abstraction for this operation anyway. The idea is to
make a kind of subclass of vector which knows what type of sequence
to "revert" to. So instead of keeping the old sequence around only for it's
type, you use a word like this:
: revert ( special-vector -- seq ) ... ;
and it does the right thing.
Subset would look like this given that mechanism:
: subset ( seq quot -- seq ) over <reverter> -rot (subset) revert ;
A benefit of this abstraction is that you eliminate a space on the data or
retain stacks. This is very helpful in the implementation of complex words
which have a big stack footprint.
Ed
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