Availability:built-in
atom_number(?Atom, 
?Number)Realises the popular combination of atom_codes/2 
and number_codes/2 
to convert between atom and number (integer, float or non-integer 
rational) in one predicate, avoiding the intermediate list. Unlike the 
ISO standard number_codes/2 
predicates, atom_number/2 
fails silently in mode (+,-) if Atom does not represent a 
number.