>Because you are attempting to combine two different datatypes -
>it also fires an error if you do this
>

>Release x
>x=null
>? x+1

>or this
>

>Release x
>x=null
>? x+" some text"

>or this
>

>Release x
>x=1
>? x+" some text"

Actually, you can do things with vars with a .NULL. value:

RELEASE x
x=.null. &&Because x was not initialized, VFP uses the logical Datatype (.F. is the default value of a variable)
? x and .T.
x=""
x=.null.
? x+""
x=0
x=.null.
? x+1
x=DATE()
x=.null.
? DTOC(x)
x=DATETIME()
x=.null.
? TTOC(x)

It all depends what the type of the variable was before .NULL. was stored into it. IOW: x=.NULL. will not change the type of the variable, it just changes it value to .NULL.

Regards,