reading and writing terms

[mvolkmann]

The basic code below is able to write a term to a file, but cannot read it back in.
The file "term.txt" does end up containing "myStructure(a1,a2)", I just can't read that file to recreate the term.
To run this I enter scryerp -g run,halt read_write.pl.
I get the error "error(syntax_error(incomplete_reduction),read_term/3:0)".
Can anyone spot what I'm doing wrong?

:- use_module(library(format)).

run :-
  File = "term.txt",
  Term = myStructure(a1, a2),
  Options = [],

  open(File, write, Stream1),
  write_term(Stream1, Term, Options),
  close(Stream1),

  open(File, read, Stream2),
  read_term(Stream2, Term2, Options),
  close(Stream2),

  format("Term2 = ~w~n", [Term2]).

[mthom]

read_term expects the term inside term.txt to be terminated with a period as in myStructure(a1, a2)..

[mvolkmann]

Thanks! Adding the line write(Stream1, '.') before closing Stream1 fixed the issue.

[triska]

Note that portray_clause_//1 from library(format) is ideally suited for such use cases. Sample use:

?- Term = myStructure(a1, a2),
   phrase_to_file(portray_clause_(Term), "term.txt").

It automatically adds the trailing . so that the term can be read back with read/1 and related predicates.

[mvolkmann]

I will try using portray_clause_ now.

[mvolkmann]

Using phrase_to_file(portray_clause_(Term), "term.txt") is much easier!