Reading terms from strings
Author(s): Francisco Bueno, Daniel Cabeza, Manuel Hermenegildo, Jose F. Morales.This module implements predicates for reading (parsing) terms from strings or atom codes.
Usage and interface
- Library usage:
:- use_module(library(read_from_string)). - Exports:
- Imports:
- System library modules:
dict, read, operators, port_reify. - Packages:
prelude, nonpure, condcomp, assertions, basicmodes.
- System library modules:
Documentation on exports
Usage:read_from_string(String,Term)
Read a term Term from String.
- The following properties should hold at call time:
(term_typing:nonvar/1)String is currently a term which is not a free variable.
(term_typing:var/1)Term is a free variable.
Usage:read_from_string(String,Term,Rest)
Read a term Term from String up to Rest (which is the non-parsed rest of the list).
- The following properties should hold at call time:
(term_typing:nonvar/1)String is currently a term which is not a free variable.
(term_typing:var/1)Term is a free variable.
Usage:read_from_string_opts(String,Term,Rest,Opts)
String is parsed into Term up to Rest (which is the non-parsed rest of the list). The options in Opts can be:
- variable_names(Ns)
- Read variable names in Ns.
- The following properties should hold at call time:
(term_typing:nonvar/1)String is currently a term which is not a free variable.
(term_typing:var/1)Term is a free variable.
(term_typing:nonvar/1)Opts is currently a term which is not a free variable.
Usage:read_from_string_atmvars(String,Term)
Read a term Term from String. It ignores the unparsed rest of the string (see read_from_string_atmvars/3).
- The following properties should hold at call time:
(term_typing:nonvar/1)String is currently a term which is not a free variable.
(term_typing:var/1)Term is a free variable.
Test:read_from_string_atmvars(A,T)
- If the following properties hold at call time:
(term_basic:= /2)term_basic:A=[97]
then the following properties should hold upon exit:
(term_basic:= /2)term_basic:T=a
Test:read_from_string_atmvars(A,T)
- If the following properties hold at call time:
(term_basic:= /2)term_basic:A=[49]
then the following properties should hold upon exit:
(term_basic:= /2)term_basic:T=1
Test:read_from_string_atmvars(A,T)
- If the following properties hold at call time:
(term_basic:= /2)term_basic:A=[65]
then the following properties should hold upon exit:
(term_basic:= /2)term_basic:T=A
Test:read_from_string_atmvars(A,T)
- If the following properties hold at call time:
(term_basic:= /2)term_basic:A=[102,40,97,41]
then the following properties should hold upon exit:
(term_basic:= /2)term_basic:T=f(a)
Test:read_from_string_atmvars(A,T)
- If the following properties hold at call time:
(term_basic:= /2)term_basic:A=[102,47,50]
then the following properties should hold upon exit:
(term_basic:= /2)term_basic:T=f/2
Usage:read_from_string_atmvars(String,Term,Rest)
Read a term Term from String up to Rest (which is the non-parsed rest of the list). Unquoted uppercase identifiers are read as atoms instead of variables (thus, the read term is always ground).
- The following properties should hold at call time:
(term_typing:nonvar/1)String is currently a term which is not a free variable.
(term_typing:var/1)Term is a free variable.
Test:read_from_string_atmvars(A,T,R)
- If the following properties hold at call time:
(term_basic:= /2)term_basic:A=[102,40,97,41]
then the following properties should hold upon exit:
(term_basic:= /2)term_basic:T=f(a)
(term_basic:= /2)term_basic:R=[]
Test:read_from_string_atmvars(A,T,R)
- If the following properties hold at call time:
(term_basic:= /2)term_basic:A=[102,40,97,41,32,102,111,111,32]
then the following properties should hold upon exit:
(term_basic:= /2)term_basic:T=f(a)
(term_basic:= /2)term_basic:R=[32,102,111,111,32]
Usage:read_from_atom_atmvars(Atom,Term)
Like read_from_string_atmvars/2, but reads the term Term from the atom codes in Atom.
- The following properties should hold at call time:
(term_typing:nonvar/1)Atom is currently a term which is not a free variable.
(term_typing:var/1)Term is a free variable.
Test:read_from_atom_atmvars(A,T)
- If the following properties hold at call time:
(term_basic:= /2)term_basic:A=a
then the following properties should hold upon exit:
(term_basic:= /2)term_basic:T=a
Test:read_from_atom_atmvars(A,T)
- If the following properties hold at call time:
(term_basic:= /2)term_basic:A=1
then the following properties should hold upon exit:
(term_basic:= /2)term_basic:T=1
Test:read_from_atom_atmvars(A,T)
- If the following properties hold at call time:
(term_basic:= /2)term_basic:A=A
then the following properties should hold upon exit:
(term_basic:= /2)term_basic:T=A
Test:read_from_atom_atmvars(A,T)
- If the following properties hold at call time:
(term_basic:= /2)term_basic:A=f(a)
then the following properties should hold upon exit:
(term_basic:= /2)term_basic:T=f(a)
Test:read_from_atom_atmvars(A,T)
- If the following properties hold at call time:
(term_basic:= /2)term_basic:A=f/2
then the following properties should hold upon exit:
(term_basic:= /2)term_basic:T=f/2
Usage:read_from_atom(Atom,Term)
Read the term Term from the atom codes in Atom.
- The following properties should hold at call time:
(term_typing:nonvar/1)Atom is currently a term which is not a free variable.
(term_typing:var/1)Term is a free variable.
Known bugs and planned improvements
- All predicates except read_from_atom/2 were implemented as a quick hack initially written mainly for parsing daVinci's messages. The good implementation should: a) create a read stream from a string, and b) call the standard reader.
- read_from_atom/2 is implemented using pipe/2, which has deadlock problems (IO is synchronous and pipe buffer size is limited)
