http://d.puremagic.com/issues/show_bug.cgi?id=5023

           Summary: Docs about order of execution of invariant and
                    pre/post conditions
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: spec
          Severity: normal
          Priority: P2
         Component: websites
        AssignedTo: nobody@puremagic.com
        ReportedBy: bearophile_hugs@eml.cc


--- Comment #0 from bearophile_hugs@eml.cc 2010-10-09 06:35:21 PDT ---
This D2 docs page states: http://www.digitalmars.com/d/2.0/class.html#invariants

> The invariant is checked when a class constructor completes, at the start of the class destructor, before a public or exported member is run, and after a public or exported function finishes.


If preconditions, postconditions and invariants are pure functions then they need to refuse the usage of functions like printf() inside them. If they aren't pure (maybe because they must support printing and logging), then printing and logging is a side effect, and their order of execution counts.

Even if preconditions, postconditions and invariants are pure functions, their purpose is to stop the execution of the program when there's a bug, so during debugging it's important to know the order of execuction of those contracts, to understand where the bug is.

Either way, the order of execution of preconditions, postconditions and invariants is important and it needs to be stated in the D documentation (and it needs to be the same in different D implementations).

So I suggest to change the D docs like this:

> The invariant is checked when a class constructor completes, at the start of
> the class destructor, before a public or exported member is run (before its precondition),
> and after a public or exported function finishes (after its postcondition).

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--- Comment #1 from bearophile_hugs@eml.cc 2010-10-09 06:36:54 PDT ---
See bug 5024

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugzilla@digitalmars.com


--- Comment #2 from Walter Bright <bugzilla@digitalmars.com> 2012-01-19 13:57:27 PST ---
Fixed, but the order is preconditions, invariant, body, invariant, postconditions.

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


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--- Comment #3 from Walter Bright <bugzilla@digitalmars.com> 2012-01-19 13:58:09 PST ---
*** Issue 5024 has been marked as a duplicate of this issue. ***

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