>>>

>>>* this is ok
>>>? 10-3-2
>>>* typo 3 => bad result (better a syntax error !)
>>>? 10--2
>>>* Need a constraint in the grammar
>>>? 10-(-2)
>>>

>>
>>Why would that be wrong? If I substract 10 minus negative two, that is the same as 10 plus 2. What do you expect, and why?
>
>Of course, but the question is how you should write this.
>With 3 or more signs VFP fail! VFP requires brackets.
>I'd rather the obligation of the brackets with 2 signs too.
>
>Why this allow a small typo to create a valid expression,
>but that is a calculation that the programmer did not want to do!
>This may result in errors discovered after months,
>you have lots of corrupted data
>and to find the wrong expression you become crazy.
>
>The only help they can give you the language of development is the syntax,
>I prefer a rigid syntax, to avoid a future in a mental hospital.

So you're asking for is a change in grammar in the special case of a subtraction so that a unary minus will be forbidden on the right-hand side?

i.e. the following will generate error
? a --b
? a - -b
but these won't
? a+-b
? a*-b
? a/-b
? a%-b
? a^-b