>>hi Frederico,
>>
>>>Fabio, if (X = 'NULL') X is a string but if (X = null) (without '') X is really null
>>
>>Then, why VFP fire a error with this ?
>>
>>

>>x=RTRIM(NULL)
>>x=NULL
>>? x+1
>>

>>
>>Fabio

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"