>>>>As far as I know, vfp always stops evaluating the right remainder of a logical expression if the left part evaluates to an logical value that cannot be changed anymore by the right remainder. For example, in the case of IF A OR B, the B is no longer evaluated if A evaluates to True. In a same vein, in the case of IF A=0 or BB(), the function BB is not visited if A=0.
>>>>
>>>>But now I am confronted with a case in a select-sql WHERE expression, where the part to the right of the OR is visited anyhow, notwithstanding the result of the left expression.

WHERE ( MOD(A,1000)#0 OR THERMO(A) )

>>>>
>>>>Does this sound familiar to anyone here?
>>>
>>>You ignores the phase of analysis,
>>>and
>>>Check A, it should to be NULL.
>>
>>It is never NULL.
>
>Post more info.
>Look this:
>

>clear
>SET NULLDISPLAY TO "I'm null"
>CREATE CURSOR myTest (A I NULL)
>INSERT INTO myTest VALUES (5)
>INSERT INTO myTest VALUES (0)
>INSERT INTO myTest VALUES (0)
>INSERT INTO myTest VALUES (null)
>INSERT INTO myTest VALUES (2)	&& VFP don't visit THERMO here
>INSERT INTO myTest VALUES (1)	&& VFP don't visit THERMO here
>INSERT INTO myTest VALUES (7)	&& VFP don't visit THERMO here
>INSERT INTO myTest VALUES (0)
>
>SELECT 0
>
>SELECT * FROM myTest;
>	WHERE (MOD(A,1000)#0 OR THERMO(A));
>	INTO CURSOR rrr
>
>PROCEDURE THERMO(vValue)
>	? "recno()=",RECNO(),"A=",vValue
>

Here's what I get.

recno()= 1 A= 5
recno()= 1 A= 5
recno()= 1 A= 5
recno()= 2 A= 0
recno()= 3 A= 0
recno()= 4 A= I'm null
recno()= 5 A= 2
recno()= 6 A= 1
recno()= 7 A= 7
recno()= 8 A= 0

Two remarkable things:
1 The first record is processed 3 times!
2 Thermo() is processed EACH record, no matter the result of MOD(A,1000)#0. The A=0 lines should not have been in the list.

I get the same result if there is no NULL record.

The second result is what I am bringing to our attention. I actually thought that I would not be able to reproduce it with such simple code, but you did.