How to determine a function existance

[Vladimir Grigoriev]

Hi
How to determine in Clipper program that a specified by a user function (for example through GET command) exists?
I.e. a user inputs a macro expression containing function name &SomeUDF and there is a need to determine does exist a function with name SomeUDF() or does not.
Vladimir Grigoriev

[Antonio Linares]

Vladimir,

You may use Type( "FunctionName()" ) or better, Type( cExpression )

[Vladimir Grigoriev]

Antonio
Yesterday I tested a simple code and got the following results.

Code: Select all

PROCEDURE MAIN()

? TYPE( "DEFINED()" ), TYPE( "2 + DEFINED()" )
? TYPE( "DEFINED() + ABS()" ), TYPE( "ABS()" )
? TYPE( "UNDEFINED()" ), TYPE( "2 + UNDEFINED()" )
? TYPE( "ABS() + UNDEFINED()" )

RETURN

FUNCTION DEFINED()
RETURN ( NIL )

UI UI UE UE U U UE

The last result "UE" destroys all concept to use TYPE( cExp ).

Vladimir Grigoriev

[Antonio Linares]

Vladimir,

It looks ok to me, as there is an undefined function in the expression.

[Vladimir Grigoriev]

And you consider that TYPE( "ABS()" ) and ? TYPE( "ABS() + UNDEFINED()" ) both return "UE" is correct?

Vladimir Grigoriev

[Badara Thiam]

Type() return the type of an expression by evaluate the expression.

You want to know if a function is linked in your executable ?
In this case, you can use Error system to intercept the error
returned if you do something like this :

************
function Test()
************
local cFunction := "MyFunc"
begin sequence
&(cFunction)()
end


When a function is not present in the exe, the error number
is always the same...


Regards,

[Vladimir Grigoriev]

I did not test but can be a such situation that BEGIN SEQUENCE will intercept an error which occured inside MyFunc() and wil be difficult to distinguish if the error is generated by the absence of the function or by the function itself?

[Antonio Linares]

Vladimir,

You may also modify Clipper errorsys and check for "undefined function" error.

[Vladimir Grigoriev]

This is an idea! It need to be tested.