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