trusty (3) erl_format.3erl.gz

NAME

       erl_format - Create and Match Erlang Terms

DESCRIPTION

       This  module  contains  two routines - one general function for creating Erlang terms and one for pattern
       matching Erlang terms.

EXPORTS

       ETERM *erl_format(FormatStr, ... )

              Types:

                 char *FormatStr;

              This is a general function for creating Erlang terms using a format specifier and a  corresponding
              set of arguments, much in the way printf() works.

              FormatStr is a format specification string. The set of valid format specifiers is as follows:

                * ~i - Integer

                * ~f - Floating point

                * ~a - Atom

                * ~s - String

                * ~w - Arbitrary Erlang term

              For  each  format  specifier  that  appears  in  FormatStr, there must be a corresponding argument
              following FormatStr. An Erlang term is built according to the FormatStr  with  values  and  Erlang
              terms  substituted  from  the  corresponding  arguments  and  according  to  the individual format
              specifiers. For example:

              erl_format("[{name,~a},{age,~i},{data,~w}]",
                         "madonna",
                         21,
                         erl_format("[{adr,~s,~i}]","E-street",42));

              This   will   create   an   (ETERM   *)   structure   corresponding   to    the    Erlang    term:
              [{name,madonna},{age,21},{data,[{adr,"E-street",42}]}]

              The function returns an Erlang term, or NULL if FormatStr does not describe a valid Erlang term.

       int erl_match(Pattern, Term)

              Types:

                 ETERM *Pattern,*Term;

              This  function  is  used  to  perform pattern matching similar to that done in Erlang. Refer to an
              Erlang manual for matching rules and more examples.

              Pattern is an Erlang term, possibly containing unbound variables.

              Term is an Erlang term that we wish to match against Pattern.

              Term and Pattern are compared, and any unbound variables in Pattern  are  bound  to  corresponding
              values in Term.

              If  Term  and  Pattern can be matched, the function returns a non-zero value and binds any unbound
              variables in Pattern. If Term Pattern do not match, the function returns 0. For example:

              ETERM *term, *pattern, *pattern2;
              term1    = erl_format("{14,21}");
              term2    = erl_format("{19,19}");
              pattern1 = erl_format("{A,B}");
              pattern2 = erl_format("{F,F}");
              if (erl_match(pattern1, term1)) {
                /* match succeeds:
                 * A gets bound to 14,
                 * B gets bound to 21
                 */
                ...
              }
              if (erl_match(pattern2, term1)) {
                /* match fails because F cannot be
                 * bound to two separate values, 14 and 21
                 */
                ...
              }
              if (erl_match(pattern2, term2)) {
                /* match succeeds and F gets bound to 19 */
                ...
              }

              erl_var_content() can be used to retrieve the content of any variables bound as a result of a call
              to erl_match().