Use of [noDefaultConstructor]

[Harrison Pratt]

The Language Reference is not completely clear on use of noDefaultConstructor. It took me a while to sort out that it needs to follow the open statements. Perhaps the LR could be clarified on the next iteration of VIP.

Code: Select all

class graphParms : graphParms
            [noDefaultConstructor]
            
    open core   % <== SYNTAX ERROR HERE
    open vpiDomains
 
constructors
 
    new : ( string GraphTypeID ).
    new_fromFile : ( string QFN ).

This compiles without error:

Code: Select all

class graphParms : graphParms
 
    open core
    open vpiDomains
 
            [noDefaultConstructor]  % <== Must follow 'open' statements
 
constructors
 
    new : ( string GraphTypeID ).
    new_fromFile : ( string QFN ).

[Thomas Linder Puls]

To a (lazy) person that already know where to write such attributes and who also have to write the language reference; it seem sufficient to write:

The attributes of interfaces, classes and implementations are right after the scope qualifications.

Which is what that lazy person wrote in the language reference: Attributes: Insertion Points.

But in reality it clearly is not sufficient. Maybe you could assist with suggesting what (in some details) you think would have helped you. (E.g. a better formulation; another location to write about it; explicit examples).

[Harrison Pratt]

Thomas,
Here's what led me astray:
http://wiki.visual-prolog.com/index.php ... onstructor

Example
class classWithoutPublicConstructors : myInterface
[noDefaultConstructor]
...
end class classWithoutPublicConstructors

In that example, the close spacing between the class declaration and [noDefaultContructor] led me to believe that [noDefaultConstructor] should immediately follow the declaration.

I did not think to search for Insertion Points ... actually, I had never read that until now! (oops!)

Perhaps modifying the example to read somewhat like the following would help:

Example
class classWithoutPublicConstructors : myInterface
open core
[noDefaultConstructor]
...
end class classWithoutPublicConstructors

[Thomas Linder Puls]

Yes, good idea. I have done that.

[Harrison Pratt]

You are too hard on the people who compiled the excellent on-line reference material -- it is hard for experts to anticipate all the possible misinterpretations made by amateurs!