[danprager]

Most languages short-circuit ands and ors already, but adding additional short-circuiting demands macros:

My practical example of this is my desire for a short-circuit "implies" operator to use in assertions (typically in post-conditions).

I want to able to write checks like

  assert (foo != null _implies_ foo.someProperty);

where the _implies_ operator short-circuits.

Writing my own implies(a,b) function is no good in most languages, because strict evaluation would yield a null-reference exception in the example when a is null.

Without macros I end-up writing:

  assert(a == null || a.someProperty); 

or worse

  if (a != null) { assert(a.someProperty);

With lisp-strength macros I could easily add an implies operator and get readable rather than clever code.