Comparing Exceptions and Errors

[Ola Fosheim Grøstad]

On Sunday, 5 June 2022 at 14:24:39 UTC, Ali Çehreli wrote:
>   void add(int i) {    // <-- Both arrays always same size
>     a ~= i;
>     b ~= i * 10;
>   }
>
>   void foo() {
>     assert(a.length == b.length);  // <-- Invariant check
>     // ...
>   }

Maybe it would help if we can agree that this assert ought to be 
statically proven to hold and the assert would therefore never be 
evaluated in running code. Emitting asserts is just a sign of 
failed statical analysis (which is common, but that is the most 
sensible interpretation from a verification viewpoint).

The purpose of asserts is not to test the environment. The 
purpose is to "prove" that the specified invariant of the 
function holds for all legal input.

It follows that the goal of an assert is not to test if the 
program is in a legal state!

I understand why you say this, but if this was the case then we 
could not remove any asserts by statical analysis. :-/