blocks3.lp

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% File: blocks.lp: Blocks World
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% sort and object declaration
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% every block is a location 
location(B) :- block(B).
% the table is a location 
location(table).

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% state description
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% two blocks can't be on the same block at the same time
:- 2{on(BB,B,T)}, block(B), T = 0..tt.

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% effect and preconditions of action
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% effect of moving a block 
on(B,L,T+1) :- move(B,L,T).
% concurrent actions are limited by num of grippers
:- not {move(BB,LL,T)} grippers, T = 0..tt-1.
% a block can be moved only when it is clear
:- move(B,L,T), on(B1,B,T).
% a block can't be moved onto a block that is being moved also
:- move(B,B1,T), move(B1,L,T).

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% domain independent axioms
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% fluents are initially exogenous 
1{on(B,LL,0):location(LL)}1 :- block(B).
% uniqueness and existence of value constraints
:- not 1{on(B,LL,T)}1, block(B), T=1..tt.
% actions are exogenous
{move(B,L,T)} :- block(B), location(L), T = 0..tt-1.
% commonsense law of inertia
{on(B,L,T+1)} :- on(B,L,T), T < tt.

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% finding plans when executed concurrently produce same result as when they are executed serially.
:- move(B, L, T), move(B1, L1, T), L != table, on(B1, L, T), B != B1.
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#show move/3.