Chars is the list of character codes comprising the printed representation of Number. Initially, either Number must be instantiated to a number, or Chars must be instantiated to a proper list of character codes.
If Number is initially instantiated to a number, Chars
is unified with the list of character codes that make up its
printed representation. If Number is uninstantiated and
Chars is initially instantiated to a list of characters that
corresponds to the correct syntax of a number (either integer or float),
Number is bound to that number; otherwise
number_chars/2 will simply fail. If the arguments to
number_chars/2 are both uninstantiated, it signals an error.
number_chars/2 was built into the system in Release 2.0. Before that,
it was a library predicate.
library(strings) still contains the old
code under the name