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erl_format(3erl) | C Library Functions | erl_format(3erl) |
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;
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 valid format specifiers
are as follows:
For each format specifier included in FormatStr, there must be a
corresponding argument following FormatStr. An Erlang term is built
according to FormatStr with values and Erlang terms substituted from
the corresponding arguments, and according to the individual format
specifiers. For example:
int erl_match(Pattern, Term)
- *
- ~i - Integer
- *
- ~f - Floating point
- *
- ~a - Atom
- *
- ~s - String
- *
- ~w - Arbitrary Erlang term
erl_format("[{name,~a},{age,~i},{data,~w}]", "madonna", 21, erl_format("[{adr,~s,~i}]","E-street",42));This creates 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.
Types:
ETERM *Pattern,*Term;
This function is used to perform pattern matching similar to that done in
Erlang. For matching rules and more examples, see section Pattern
Matching in the Erlang Reference Manual.
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 and Pattern do not match, 0 is returned. For
example:
- *
- Pattern is an Erlang term, possibly containing unbound variables.
- *
- Term is an Erlang term that we wish to match against Pattern.
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().
erl_interface 3.9.2 | Ericsson AB |