ram_simulator.pl : Simulates a Random Access Machine Simulates a Random Access Machine (RAM) that is an abstract machine consisting of memory cells (mem), program instructions (prog) and a program instruction counter (prog_counter). The instruction pointed to by the prog_counter is executed, thereby accessing the memory and updating the prog_counter.
How to use: The memory cell with label L and value V is represented as mem(L,V). The program counter pointing to P is represented as prog_counter(P). A program instruction has the form prog(L,L1, Instr, Dest): prog_counter(P) selects the instruction for which L=P. After executing the instruction prog_counter is set to L1 by default. Instr and Dest specify the instruction and destination. [For more please consider DETAILS in the comment.]
See also: (1) John E. Savage. Models of Computation: Exploring the Power of Computing. Addisson-Wesley, ISBN 0-201-89539-0, 1998. (2) http://en.wikipedia.org/wiki/Random_Access_Machine
Program: Change the code, then submit! /* ram_simulator.pl: Simulates a Random Access Machine (C) Jon.Sneyers at cs.kuleuven.be (C) Tom.Schrijvers at cs.kuleuven.be This program is distributed under the terms of the GNU General Public License: http://www.gnu.org/licenses/gpl.html %% DESCRIPTION Simulates a Random Access Machine (RAM) that is an abstract machine consisting of memory cells (mem), program instructions (prog) and a program instruction counter (prog_counter).# The instruction pointed to by the prog_counter is executed, thereby accessing the memory and updating the prog_counter. %% HOW TO USE The memory cell with label L and value V is represented as *mem(L,V)*. The program counter pointing to P is represented as *prog_counter(P)*. # A program instruction has the form *prog(L,L1, Instr, Dest)*: *prog_counter(P)* selects the instruction for which L=P. After executing the instruction *prog_counter* is set to L1 by default. Instr and Dest specify the instruction and destination.# [For more please consider DETAILS in the comment.] %% DETAILS The following instructions are supported: # * *prog(L,L1,add(B),A)*: A:=A+B (add value of register B to register A) # * *prog(L,L1,sub(B),A)*: A:=A-B (subtract value of register B from register A) # * *prog(L,L1,mult(B),A)*: A:=A*B (multiply register A with value of register B)# * *prog(L,L1,div(B),A)*: A:=A/B (divide register A by value of register B) # * *prog(L,L1,move(B),A)*: A:=B (put the value in register B in register A) # * *prog(L,L1,i_move(B),A)*: A:=[B] (put the value in register <value in register B> in register A) # * *prog(L,L1,move_i(B),A)*: [A]:=B (put the value in register B in register <value in register A>) # * *prog(L,L1,const(B),A)*: A:=#B (put the value B in register A) # * *prog(L,_,jump,A)*: PC:=#A (unconditional jump to label A) # * *prog(L,L1,cjump(R),A)*: if R=0 then PC:=#A else PC:=#L1 (jump to label A if register R is zero, otherwise continue) # * *prog(L,_,halt,_)*: PC:=undef (halt) %% SEE ALSO (1) John E. Savage. Models of Computation: Exploring the Power of Computing. Addisson-Wesley, ISBN 0-201-89539-0, 1998. # (2) http://en.wikipedia.org/wiki/Random_Access_Machine %% SAMPLE QUERIES Q: mem(1,1), mem(2,10000), mem(3,0), prog_counter(1), prog(1,2, add(1), 3), prog(2,3, sub(1), 2), prog(3,1, cjump(2), 4), prog(4,0, halt, 0). A: mem(1,1), mem(2,0), mem(3,10000), ... % emulate division Q: mem(a,17), mem(b,3), mem(r,0), mem(c1,1), mem(t,0), prog_counter(0), prog(0,1, add(c1), a), prog(1,2, move(b), t), prog(2,3, sub(c1), t), prog(3,4, sub(c1), a), prog(4,5, cjump(a), end), prog(5,2, cjump(t), 6), prog(6,1, add(c1), r), prog(end,0, halt, 0). A: mem(a,0), mem(b,3), mem(r,5), mem(c1,1), mem(t,0), ... */ :- module(ram_simulator, [mem/2, prog/4, prog_counter/1]). :- use_module(library(chr)). %% Deprecated syntax used for SICStus 3.x %handler ram_simulator. %constraints mem/2, prog/4, prog_counter/1. %% Syntax for SWI / SICStus 4.x :- chr_constraint mem(+int,?int), prog(+int,+int,+any,?int), prog_counter(?int). % add value of register B to register A prog(L,L1,add(B),A), mem(B,Y) \ mem(A,X), prog_counter(L) <=> Z is X+Y, mem(A,Z), prog_counter(L1). % subtract value of register B from register A prog(L,L1,sub(B),A), mem(B,Y) \ mem(A,X), prog_counter(L) <=> Z is X-Y, mem(A,Z), prog_counter(L1). % multiply register A with value of register B prog(L,L1,mult(B),A), mem(B,Y) \ mem(A,X), prog_counter(L) <=> Z is X*Y, mem(A,Z), prog_counter(L1). % divide register A by value of register B prog(L,L1,div(B),A), mem(B,Y) \ mem(A,X), prog_counter(L) <=> Z is X//Y, mem(A,Z), prog_counter(L1). % put the value in register B in register A prog(L,L1,move(B),A), mem(B,X) \ mem(A,_), prog_counter(L) <=> mem(A,X), prog_counter(L1). % put the value in register <value in register B> in register A prog(L,L1,i_move(B),A), mem(B,C), mem(C,X) \ mem(A,_), prog_counter(L) <=> mem(A,X), prog_counter(L1). % put the value in register B in register <value in register A> prog(L,L1,move_i(B),A), mem(B,X), mem(A,C) \ mem(C,_), prog_counter(L) <=> mem(C,X), prog_counter(L1). % put the value B in register A -> redundant if consts are in init mem prog(L,L1,const(B),A) \ mem(A,_), prog_counter(L) <=> mem(A,B), prog_counter(L1). % unconditional jump to label A prog(L,_,jump,A) \ prog_counter(L) <=> prog_counter(A). % jump to label A if register R is zero, otherwise continue prog(L,_,cjump(R),A), mem(R,X) \ prog_counter(L) <=> X == 0 | prog_counter(A). prog(L,L1,cjump(R),_), mem(R,X) \ prog_counter(L) <=> X =\= 0 | prog_counter(L1). % halt prog(L,_,halt,_) \ prog_counter(L) <=> true.
Console: Enter query or select example from below, then submit and wait for answer! % loading misc/ram_simulator.pl | ?- consult(...). yes [8.623 seconds] | ?-