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read_term(+Stream, -Term, ++Options)
Read a whole term in ECLiPSe syntax from the input stream Stream, according to Options
- Stream
- Integer (stream number) or Atom (reserved or user-defined symbolic stream name)
- Term
- An term, usually a variable
- Options
- List of option terms
Description
This is a generalisation of the predicates read/2 and readvar/3.
Options is a (possibly empty) list of the following options:
- variables(Vars)
returns a duplicate-free list of all the variables in the term
that has been read (including anonymous variables).
- variable_names(VarsNames)
returns a duplicate-free list of structures of the form
Name=Var, where Var is a named (non-anonymous) variable which
occurs in the term that has been read, and Name is an atom,
representing the source name.
- singletons(VarsNames)
returns a list of structures of the form Name=Var, where Var
is a named (non-anonymous) variable which occurs only once in
the term that has been read, and Name is an atom, representing
the source name.
Modes and Determinism
- read_term(+, -, ++) is semidet
Modules
This predicate is sensitive to its module context (tool predicate, see @/2).
Fail Conditions
Fails if a syntax error was detected and no term could be read
Exceptions
- (4) instantiation fault
- Stream is not instantiated.
- (5) type error
- Stream is not an atom or an integer.
- (5) type error
- Options is not a list of compound terms.
- (6) out of range
- Options list contains a unrecognised option.
- (192) illegal stream mode
- Stream is not an input stream.
- (193) illegal stream specification
- Stream is an illegal stream specification.
Examples
?- read_term(T, []).
foo(X,_,bar(X,Y,_Z)).
T = foo(X, _255, bar(X, Y, _Z))
?- read_term(T, [variable_names(VN)]).
foo(X,_,bar(X,Y,_Z)).
T = foo(X, _260, bar(X, Y, _Z))
VN = ['X' = X, 'Y' = Y, '_Z' = _Z]
?- read_term(T, [variables(V),variable_names(VN),singletons(S)]).
foo(X,_,bar(X,Y,_Z)).
T = foo(X, _278, bar(X, Y, _Z))
V = [X, _278, Y, _Z]
VN = ['X' = X, 'Y' = Y, '_Z' = _Z]
S = ['_Z' = _Z, 'Y' = Y]
See Also
read_term / 2, readvar / 3, read / 1, read / 2, set_stream_property / 3