Data commit

Task/Universal-Turing-machine/MATLAB/universal-turing-machine.m

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+function tape=turing(rules,tape,initial,terminal)
+    %"rules" is cell array of cell arrays of the following form:
+    %First element is number representing initial state
+    %Second element is number representing input from the tape
+    %Third element is number representing output printed onto the tape
+    %Fourth element is 'l', 'r', or 's' representing whether to go right,
+    %left, or stay. Treats any input other than 'l' or 'r' as 's'.
+    %Final value is state we go to
+    %0 is always blank symbol
+    term=0;
+    ind=1;
+    while term==0
+        a=[];
+        for i=1:numel(rules)
+            if rules{i}{1}==initial
+                a=[a i];
+            end
+        end
+
+        possible=rules(a);
+        n=numel(possible);
+
+        while numel(tape)<ind
+            tape=[tape, 0]; %#ok<AGROW>
+        end
+
+        for i=1:n
+            if(tape(ind)==possible{i}{2})
+                break;
+            end
+        end
+        instruction=possible{i};
+        tape(ind)=instruction{3};
+        if instruction{4}=='r'
+            ind=ind+1;
+        elseif instruction{4}=='l'
+            if ind==1
+                tape=[0,tape]; %#ok<AGROW>
+            else
+                ind=ind-1;
+            end
+        end
+        if terminal==instruction{5}
+            term=1;
+        else
+            initial=instruction{5};
+        end
+    end
+end