[plt-dev] define +1

 > (define (+1 x) x)
readline::57: define: bad syntax (not an identifier for procedure name, 
and not a nested procedure form) at: 1 in: (define (1 x) x)

 > (define (-1 x) x)
readline::75: define: bad syntax (not an identifier for procedure name, 
and not a nested procedure form) at: -1 in: (define (-1 x) x)

I guess +1 and -1 are parsed as numbers, which aren't included as 
identifiers. Is this fixable?