strange behavior of by-value function arguments in postcondition

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On Wednesday, 1 September 2021 at 06:14:27 UTC, bauss wrote:
> Pre/post conditions _are_ assert statements tho. User 
> validation should be done using exceptions, not asserts.

The fact that they are assert statements is an implementation 
detail. The point of pre/post conditions is to enforce that 
certain properties of the function hold, and assertions are just 
how the language happens to implement that.