Availability:built-in
syntax_error if Number is unbound or CharList 
does not describe a number. Following the ISO standard, it allows for
leading white space (including newlines) and does not allow for
trailing white space.101ISO 
also allows for Prolog comments in leading white space. We--and most 
other implementations--believe this is incorrect. We also beleive it 
would have been better not to allow for white space, or to allow for 
both leading and trailing white space. Prolog syntax-based conversion 
can be achieved using format/3 
and read_from_chars/2.