Safe-dereference operator?

[Frank Ch. Eigler]

craig wrote:

> TL;DR: Proposal to add a safe-dereference pseudo-operator like Groovy's ?.
> to the language to simplify chasing pointer chains.
> ?. is basically an abbreviated ternary without the multiple-evaluation
> hazard:
>    a ?. b ?. c

This sounds like something that can be done via a macro
(tapset/SOMETHING.stpm) with a functional syntax, if you
can accept the multiple-evaluation problem:

@define pointer_chase_1(a,b) %( @a ? @a->@b : 0 %)
@define pointer_chase_2(a,b,c) %( @a ? (@a->@b ? @a->@b->@c : 0) : 0 %)

If you can't ... can you explain why?  Must those index
fields depend on state-modifying calculations?

- FChE