PLOGHELP SIMPLEPOP                          Jonathan Laventhol July 1983
                                 Revised by Kathryn Seifert  August 1986

Library package to do simple things in Pop11 from Prolog

Keywords: Pop11, Prolog, mixed language programming, library


CONTENTS - (Use <ENTER> g to access sections)

 -- INTRODUCTION
 -- SIMPLEST FORM
 -- GETTING RESULTS
 -- ERROR RECOVERY
 -- VARIABLES
 -- QUOTE SIGNS INSIDE THE POP-11 CODE
 -- STRINGS, WORDS AND ATOMS
 -- RELATED DOCUMENTATION


-- INTRODUCTION -------------------------------------------------------

If you want to do fairly simple things in Pop11 from within Prolog,
there is a library package, SIMPLEPOP, to help you.  If you want the
full flexibility, you should see PLOGHELP * PLOGTOPOP and
PLOGHELP * MIXED_LANGUAGES.

SIMPLEPOP allows you to use normal Pop11 syntax. It provides three
predicates: dopop/1, dopop/2, and dopopreturn/2. These predicates are
explained below.

To load LIBRARY SIMPLEPOP, type:

    ?- library(simplepop).


-- SIMPLEST FORM ------------------------------------------------------

Once you have the library file loaded you can give a string or an atom
of Pop11 code to the Prolog predicate dopop/1:

    ?- dopop("1234 =>").
    ** 1234
    yes

If the Pop11 code leaves results on the stack then they will be ignored;
if a mishap happens the goal fails.


-- GETTING RESULTS ----------------------------------------------------

If you want to get results back from the Pop11 code, use dopop/2 -- a
list of the results, if any, will be unified with the second argument:

    ?- dopop("100 + 2; 300 + pi", Results).
    Results = [102, 303.142] ?
    yes


-- ERROR RECOVERY -----------------------------------------------------

If you really want to get the mishap message, you can use dopopreturn/2.
This is like dopop/2, but if there is a mishap, then a Prolog term
indicating the error will be unified with the results variable:

    ?- dopopreturn("100 + nil", X).
    X = pop_mishap(NUMBER(S) NEEDED, [100, []], [+, sysEXECUTE,
            pop11_exec_stmnt_seq_to, sysCOMPILE, pop11_comp_stream,
            compile]) ?
    yes

The term 'pop_mishap' has three arguments -- the error message, the
"culprits", and a shortened list of the calling sequence.


-- VARIABLES ----------------------------------------------------------

To set a Pop11 variable do:

    ?- dopop("78 -> poplinemax;").

To examine a Pop11 variable do:

    ?- dopop("poplinemax", Poplinemax).
    Poplinemax = 78 ?

See HELP * POPVARS for a list of variables which it might be useful to
set.


-- QUOTE SIGNS INSIDE THE POP-11 CODE ---------------------------------

If you need the double quote sign in the Pop11 code, then you should
give the Pop11 code in an atom:

    ?- dopop(' "hello" => ').
    ** hello
    yes

If you need single quotes, make sure you use a Prolog string:

    ?- dopop(" 'hello there' => ").
    ** hello there
    yes

If you need both, do this:

    ?- dopop(' \'hello\' >< "there" => ').
    ** hellothere
    yes


-- STRINGS, WORDS AND ATOMS -------------------------------------------

In Pop11,

    Strings are surrounded by single quotes: 'a pop11 string'.
    Words are surrounded by double quotes: "aword"
    Values of variables have no quotes

In Prolog,

    Strings are surrounded by double quotes: "a prolog string".
    Atoms are surrounded by single quotes if they have certain characters
    in them: 'a funny atom'


-- RELATED DOCUMENTATION ----------------------------------------------

PLOGHELP * ARE
 Library for evaluating Pop11 expressions with any number of
 results from Prolog

PLOGHELP * IS
 Evaluating Pop11 expressions which return 1 result from Prolog

PLOGHELP * LIBRARIES
 Overview of Prolog library programs

PLOGHELP * MIXED_LANGUAGES
 Overview of methods of interfacing Prolog and other languages

PLOGHELP * PLOGTOPOP
 How to call Pop11 from Prolog

PLOGHELP * POPSTRING
 How to put Pop11 strings in Prolog programs

PLOGHELP * POPTOPLOG
 How to call Prolog from Pop11

PLOGHELP * PROLOG_EVAL
 How to evaluate the Prolog representation of a Pop11 expression

PLOGHELP * PROLOG_LANGUAGE
 Predicates and library package for switching from Prolog to Pop11

PLOGHELP * PROLOG_SETQ
 reading and writing Pop11 variables from Prolog.

PLOGHELP * TERMSINPOP
 Facilities for manipulating Prolog terms and variables in Pop11


--- C.all/plog/help/simplepop ------------------------------------------
--- Copyright University of Sussex 1991. All rights reserved. ----------