39daac182e
We still need to support futher builtins. git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1590 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
382 lines
9.8 KiB
HTML
382 lines
9.8 KiB
HTML
BEAM How-to-get-started
|
|
|
|
This document gives you an introduction on how to use the EAM withing YAP.
|
|
We start by explaining how to prepare YAP to use the EAM.
|
|
Then we present some code examples that you can use to try
|
|
out the EAM.
|
|
|
|
|
|
WARNING:
|
|
THE BEAM WITHING YAP IS STILL IN EARLY DEVELOPMENT,
|
|
SO DON'T EXPECT IT TO RUN SMOOTHLY...
|
|
WE ARE WORKING TO IMPROVE THE INTEGRATION OF BEAM WITHIN
|
|
YAP, BUT THIS THINGS TAKE TIME. SO PLEASE BE PATIENT...
|
|
|
|
|
|
---------------------------------------------------------------------------
|
|
1. Compiling Yap to support the EAM.
|
|
---------------------------------------------------------------------------
|
|
If you want to use the BEAM prototype you must compile YAP using the
|
|
flag --enable-eam
|
|
|
|
tar -xvzf yapfile.tar.gz <- will extract yap to $YAPDIR
|
|
mkdir tmp
|
|
cd tmp
|
|
../YAPDIR/configure --enable-eam <- prepare yap to compilation
|
|
make <- compile yap
|
|
su <- enter as root
|
|
make install <- install yap
|
|
|
|
You are now ready to try YAP-BEAM. Just run "yap" on the
|
|
command line.
|
|
|
|
|
|
---------------------------------------------------------------------------
|
|
2. Quick start + Examples...
|
|
---------------------------------------------------------------------------
|
|
Quick example on how to run a Prolog program using the EAM.
|
|
|
|
-FIRST ALTERNATIVE:
|
|
Consult your program using eamconsult(+File)
|
|
?- eamconsult(qsort).
|
|
|
|
then you should write your queries using ?- eam(query).
|
|
You can write the query normally as in normal Prolog mode, but
|
|
in this case you will only receive the first solution (or yes or no).
|
|
|
|
The eamconsult will pre-compile your prolog code to control
|
|
cases where changing the order in execution can be problematic...
|
|
For example consider the query: ?- g(X), f(X).
|
|
Supose that g/1 is non-deterministic and that f/1 has a single clause.
|
|
The EAM engine will try to execute f/1 first, since it is deterministic.
|
|
Now supose that f/1 depends on a bound argument, for example:
|
|
f(X):- X > 1, ...
|
|
|
|
The eamconsult will be transform this code into
|
|
f(X):- skip_while_var([X]), X>1, ...
|
|
|
|
The skip_while_var/1 will not allow the comparision X>1 to be executed
|
|
while X is unbound.
|
|
|
|
|
|
|
|
-SECOND ALTERNATIVE:
|
|
|
|
|
|
First you must enable the EAM using the comand
|
|
?- eam.
|
|
yes
|
|
|
|
then you should load your program, and make your queries
|
|
using ?- eam(query).
|
|
You can write the query normally as in normal Prolog mode, but
|
|
in this case you will only receive the first solution (or yes or no).
|
|
|
|
|
|
Small example:
|
|
Supose that you have the file Example.pl with the Prolog code:
|
|
f(1).
|
|
f(2).
|
|
f(3).
|
|
|
|
Here is an execution example:
|
|
[user]$ ./yap
|
|
% Restoring file /.../startup
|
|
YAP version Yap-5.0.0
|
|
?- eam.
|
|
yes
|
|
?- [t].
|
|
% consulting /.../t.pl...
|
|
% consulted /.../t.pl in module user, 1 msec 1328 bytes
|
|
yes
|
|
?- eam(f(X)).
|
|
[ EAM execution started to solve f/1 ]
|
|
X = 1 ? ;
|
|
X = 2 ? ;
|
|
X = 3 ? ;
|
|
no
|
|
?- f(X).
|
|
[ EAM execution started to solve f/1 ]
|
|
X = 1 ? ;
|
|
no
|
|
?-
|
|
|
|
---------------------------------------------------------------------------
|
|
A first example:
|
|
|
|
You can try out the next example, the well-known benchmark scanner.pl
|
|
that behaves badly in standard Prolog systems.
|
|
Just run the demos... (demo1, demo2, demo3 or demo4).
|
|
Remember to enable the EAM before loading the program.
|
|
After running the examples, try restarting YAP and
|
|
loading the program without the EAM enabled. Try to run
|
|
the demo4... :)
|
|
|
|
demo1:- demo(tiny).
|
|
demo2:- demo(small).
|
|
demo3:- demo(data).
|
|
demo4:- demo(snake).
|
|
|
|
demo(Data):-
|
|
scannerdata(Data,R,C,D1,D2),
|
|
write('Rows '), write(R),nl,
|
|
write('Columns '), write(C),nl,
|
|
write('Left diagonals '), write(D1),nl,
|
|
write('Right diagonals '), write(D2),nl,nl,
|
|
scanner(R,C,D1,D2,Image), !,
|
|
displi(Image).
|
|
|
|
sequence(Spec):-
|
|
samples(Spec,Samples),
|
|
cat(Samples,Images), !,
|
|
displ(Images).
|
|
|
|
samples([],Samples):- !, Samples=[].
|
|
samples([S|Spec],Samples):- !,
|
|
scannerdata(S,R,C,D1,D2),
|
|
Samples=[sample(R,C,D1,D2)|Smpls],
|
|
samples(Spec,Smpls).
|
|
|
|
cat([],Images):- !, Images=[].
|
|
cat([Sample|Samples], Images):- !,
|
|
image(Sample,Image),
|
|
Images=[Image|Imgs],
|
|
cat(Samples,Imgs).
|
|
|
|
image(sample(R,C,D1,D2), Image):-
|
|
scanner(proc,R,C,D1,D2,I), !,
|
|
Image=I.
|
|
|
|
|
|
displ([]):- nl, nl.
|
|
displ([I|Imgs]):- nl, displi(I), nl, displ(Imgs).
|
|
|
|
displi([]):- nl .
|
|
displi([R|Rws]):- write(' '),displr(R), displi(Rws).
|
|
|
|
displr([]):- nl.
|
|
displr([on|R]):- write('X '), displr(R).
|
|
displr([off|R]):- write('_ '), displr(R).
|
|
|
|
|
|
scannerdata(tiny, [1,1],[2,0],[1,1,0],[0,1,1]).
|
|
|
|
scannerdata(small, [1,2,1],[2,1,1],[1,1,1,0,1],[0,0,3,1,0]).
|
|
|
|
scannerdata(double,
|
|
[2,2,3,2,2,1],
|
|
[1,3,3,1,3,1],
|
|
[0,1,1,2,1,2,3,1,1,0,0],
|
|
[0,2,0,1,2,2,2,1,2,0,0]).
|
|
|
|
scannerdata(snake,
|
|
[4,2,6,2,4,4,3,2],
|
|
[3,5,5,3,2,3,3,3],
|
|
[1,2,2,1,1,2,5,2,2,3,3,2,1,0,0],
|
|
[0,1,0,3,2,2,4,3,3,3,1,3,2,0,0]).
|
|
|
|
scanner(RwData,ClData,D1Data, D2Data, Rws):-
|
|
llength(RwData,R),
|
|
llength(ClData,C),
|
|
board(R,C,All,Rws,Cls,D1,D2),
|
|
check(RwData,Rws),
|
|
check(ClData,Cls),
|
|
check(D1Data,D1),
|
|
check(D2Data,D2).
|
|
|
|
pixle(on).
|
|
pixle(off).
|
|
|
|
|
|
check([],[]).
|
|
check([K|RwsD],[R|Rws]):-
|
|
llength(R,L),
|
|
line(K,L,R),
|
|
check(RwsD,Rws).
|
|
|
|
line(0,0,[]).
|
|
line(K,L,[on|R]):-
|
|
K > 0,
|
|
K1 is K - 1,
|
|
L1 is L - 1,
|
|
line(K1,L1,R).
|
|
line(K,L,[off|R]):-
|
|
L > K,
|
|
L1 is L - 1,
|
|
line(K,L1,R).
|
|
|
|
board(0,C,[],[],Cls,D,D):-
|
|
C > 0,
|
|
C1 is C - 1,
|
|
seed(C,Cls),
|
|
seed(C1,D).
|
|
board(R,C,All,[Row|Rws],Cols,Rdiag,Ldiag):-
|
|
R > 0,
|
|
R1 is R - 1,
|
|
row(C, Row),
|
|
all2(Row,Al,All),
|
|
column(Row,Cls,Cols),
|
|
diagonal(Row,Rdg,Rdiag),
|
|
rev(Row,[],Rev),
|
|
diagonal(Rev,Ldg,Ldiag),
|
|
board(R1,C,Al,Rws,Cls,Rdg,Ldg).
|
|
|
|
seed(0,[]).
|
|
seed(C,[[]|S1]):- C > 0, C1 is C -1 , seed(C1,S1).
|
|
|
|
all2([],Al,Al).
|
|
all2([H|Row],Al,[H|All]):- all2(Row,Al,All).
|
|
|
|
row(0,[]).
|
|
row(C,[_|R]):- C > 0, C1 is C -1, row(C1,R).
|
|
|
|
column([],X,X).
|
|
column([H|R],[Cl|Cls],[[H|Cl]|Columns]):- column(R,Cls,Columns).
|
|
|
|
diagonal([H|Row],Dg, [[H]|Diag]):- column(Row,Dg,Diag).
|
|
|
|
rev([],Y,Y).
|
|
rev([H|T],Y,Z):- rev(T,[H|Y],Z).
|
|
|
|
llength([],0).
|
|
llength([A|R],N):- llength(R,M), N is M+1.
|
|
|
|
|
|
|
|
---------------------------------------------------------------------------
|
|
Another example:
|
|
|
|
The famours queens...
|
|
|
|
|
|
Try to evaluate in normal Prolog que query:
|
|
?- queens([1,2,3,4,5,6,7,8,9,10,11,12,13,14,15],X).
|
|
Now quit YAP and enable eam before loading the queens program
|
|
Here is the code for you to try it:
|
|
|
|
demo1:- queens([1,2,3,4,5,6,7,8,9],L), write(L), nl, fail.
|
|
demo2:- queens([1,2,3,4,5,6,7,8,9,10,11,12,13,14,15],L), write(L), nl.
|
|
|
|
queens(L,C):-
|
|
perm(L,P),
|
|
pair(L,P,C),
|
|
safe([],C).
|
|
|
|
perm([],[]).
|
|
perm(Xs,[Z|Zs]):-
|
|
select(Z,Xs,Ys),
|
|
perm(Ys,Zs).
|
|
|
|
select(X,[X|Xs],Xs).
|
|
select(X,[Y|Ys],[Y|Zs]):-
|
|
select(X,Ys,Zs).
|
|
|
|
pair([],[],[]).
|
|
pair([X|Y],[U|V],[p(X,U)|W]):-
|
|
pair(Y,V,W).
|
|
|
|
safe(X,[]).
|
|
safe(X,[Q|R]):-
|
|
test(X,Q),
|
|
safe([Q|X],R).
|
|
|
|
test([],X).
|
|
test([p(C1,R1)|S],p(C2,R2)):-
|
|
test(S,p(C2,R2)),
|
|
nd(p(C1,R1),p(C2,R2)).
|
|
|
|
nd(p(C1,R1),p(C2,R2)):-
|
|
wait_while_var([C1,C2,R1,R2]),
|
|
C is C1-C2,
|
|
R is R1-R2,
|
|
C=\=R,
|
|
NR is R2-R1,
|
|
C=\=NR.
|
|
|
|
Note that on the nd predicate, we have used wait_while_var
|
|
to force the EAM to wait while C1, C2, R1, R2 are not bound,
|
|
because the operations in this predicate can't be done with
|
|
those variables unbound.
|
|
Alternatively, and if you don't want to use wait_while_var,
|
|
you can compile the prolog code using eamconsult.
|
|
eamconsult will insert this instructions for you automatically.
|
|
|
|
---------------------------------------------------------------------------
|
|
3. Some notes...
|
|
---------------------------------------------------------------------------
|
|
|
|
- A lot of builtins/code are not yet supported...
|
|
For example var(X), not , ; (or), ...
|
|
You will have a internal compiler error for these cases.
|
|
and the clause that uses the builtin/code not supported will always fail.
|
|
Example: consider the code:
|
|
tst(X):- var(X), X=1.
|
|
tst(2).
|
|
|
|
You will receive a warning that there is unsupported code.
|
|
Although you can still use the tst predicate, the first alternative
|
|
will always fail...
|
|
|
|
?- tst(X).
|
|
[ EAM execution started to solve tst/1 ]
|
|
X = 2 ? ;
|
|
no
|
|
|
|
|
|
---------------------------------------------------------------------------
|
|
- The EAM prefers deterministic instead of non-deterministic.
|
|
and thus can change the order of goals of your code to delay
|
|
non-deterministic bindings.
|
|
|
|
So, you must be careful when using builtins that have side-effects,
|
|
or that may expect variables to be bound.
|
|
|
|
For example, supose that you have the following Prolog code:
|
|
f(1).
|
|
f(2).
|
|
|
|
tst(Y):- f(X), Y is X+1.
|
|
|
|
Normal prolog would be fine, but the EAM can not execute this
|
|
code correctly because since f(X) is non-deterministic,
|
|
Y is X+1 is executed before X being bound. The result would be:
|
|
|
|
?- tst(X).
|
|
[ EAM execution started to solve tst/1 ]
|
|
% INSTANTIATION ERROR- in arithmetic at user:tst/1 (clause 1): expected bound value
|
|
|
|
|
|
The solution for this case is to force the EAM to wait for X to be bound.
|
|
This can be done by using eamconsult(File) instead of the normal
|
|
consult, or by inserting the control instructions explicitly in the code.
|
|
|
|
So the code correct code would be:
|
|
tst(Y):- f(X), skip_while_var(X), Y is X+1.
|
|
|
|
That means that the code Y is X+1 should be skipped
|
|
while X is var. Note that in this case there is no more
|
|
after Y is X+1. If there were, execution would continue
|
|
on that code.
|
|
|
|
Another alternative is to use:
|
|
tst(Y):- f(X), wait_while_var(X), Y is X+1.
|
|
|
|
that means what execution can not proceed while X is not bound.
|
|
|
|
|
|
|
|
---------------------------------------------------------------------------
|
|
|
|
- To support the EAM within the YAP the WAM compilation was
|
|
specially the classification of permanent variables.
|
|
This code was adapted from the initial BEAM implementation and is not
|
|
yet completed.
|
|
I've have already discover some code examples where the variables
|
|
should are not being classified as permanent, and as result the BEAM
|
|
returns false solutions. We are also working on this problem...
|
|
|
|
---------------------------------------------------------------------------
|
|
Expect more info soon...
|
|
...
|
|
|