Return Isn't Transparent

[Howard Lovatt]

Hi Neal,

Are you saying that there are *no* cases where BGGA cannot reason
about the control flow? This is a slightly different question than
saying that a new language could not be designed with transparency in
mind.

  -- Howard.

On 18 July 2010 01:15, Neal Gafter <neal at gafter.com> wrote:
> On Sat, Jul 17, 2010 at 6:46 AM, Howard Lovatt <howard.lovatt at gmail.com>
> wrote:
>>
>> A return statement isn't transparent. This is well articulated in
>> Principles of Programming Languages R. D. Tennent (I don't have a copy
>> handy - but I think page 56 is one such place). Consider:
>>
>> int m() {
>>  return 42; // To be wrapped in a lambda
>> }
>>
>> Then imagine that you could create a lambda that encapsulated the long
>> return and you called it:
>>
>> int m() {
>>  { -> return 42; }.();
>>  // Oops error - must return value from m
>> }
>
> This works just fine in BGGA.  The language can indeed be designed so that
> return is transparent.