diff --git a/lab2-recursive-arithmetic.pl b/lab2-recursive-arithmetic.pl new file mode 100644 index 0000000..60d3c54 --- /dev/null +++ b/lab2-recursive-arithmetic.pl @@ -0,0 +1,95 @@ +% Lab 2 - Recursive Arithmetic in Prolog +% LABSHEET: +% https://teaching.csse.uwa.edu.au/units/CITS3005/labs/lab02-arithmetic.pdf + +% Build a Prolog program to do recursive arithmetic. It should have + +% 1. a constant, zero, to represent zero. +zero. + +% 2. a function, next(X), that represents the next number (so next(zero) represents one). +next(X) :- X. + +% 3. a predicate, sum(X,Y,Z), which is true if X + Y = Z. +% sum(zero,zero,Z) :- Z is zero. +% sum(zero,Y,Z) :- Z is Y. +% sum(next(zero),Y,Z) :- Z is next(Y). +sum(zero,zero,zero). % CASE 1 : 0 + 0 == 0 +sum(zero,X,X). % CASE 2 : 0 + X == X +sum(next(X),Y,next(Z)) :- sum(X,Y,Z). % CASE 3 : (X+1) + Y == (Z+1) (Works based on previous two cases???) +% TEST 1: +% sum(next(zero),next(zero),next(next(zero))) +%=sum(zero,next(zero),next(zero)) [ TRUE ] +% TEST 2: +% sum(next(next(zero)),zero,next(zero)) +%=sum(next(zero),zero,zero) [ FALSE ] + +% 4. a predicate, mult(X,Y,Z) which is true if X × Y = Z. +mult(zero,zero,zero). +mult(zero,_,zero). +mult(next(zero),X,X). +mult(next(X),Y,Z) :- mult(X,Y,Zp), sum(Y,Zp,Z). % (x+1)*y == x*y+y + +% 5. a predicate, equals(X,Y) which is true if X = Y . +equals(X,X). + +% 6. a predicate, lessThan(X,Y) which is true if X < Y ¿ +lessThan(zero,next(_)). +lessThan(next(X),next(Y)) :- lessThan(X,Y). % X+1 < Y+1 => X < Y. As X->0, Y->N => 0 < N. + +% binary_(zero,0). +% binary_(next(X),IntValue) :- binary_(X,PrevIntValue), write(PrevIntValue), IntValue is PrevIntValue+1. +% binary(X) :- binary_(X,Buffer), write(Buffer). + + +% Test your program and consider the efficinecy of the implementations. Is there a way to get faster annswers? +% Next, add additional functions: +% 1. Write a program binary(X) that will print the binary representation of X out, so for example, binary(next(next(zero) +% will print out 10. +% NOTE: Binary array is in reverse! +increment_b([],[]). +increment_b([ODigit | ORest],[Digit | Rest]) :- + ODigit =:= 0 -> Digit is 1, + equals(Rest,ORest); + ODigit =:= 1 -> Digit is 0, + ( + equals(ORest,[]) -> equals(Rest,[1]); + increment_b(ORest,Rest) + ). + +% NOTE: Binary array is in reverse! +binary_arr(zero,[0]). +binary_arr(next(X),NextBinary) :- + binary_arr(X,Binary), + increment_b(Binary,NextBinary). + +binary_arr_print([]). +binary_arr_print([Digit|Rest]) :- write(Digit), binary_arr_print(Rest). + +binary(X) :- + binary_arr(X,BinaryArrRev), + reverse(BinaryArrRev, BinaryArr), + binary_arr_print(BinaryArr). + +% 2. Implement predicates for odd, even and prime numbers. +even(zero). +even(next(X)) :- \+even(X). + +odd(X) :- \+even(X). + +% Cheating a bit here ... would be harder doing the whole primality test in the above notation, since I don't have a modulo predicate defined +to_integer(zero,0). +to_integer(next(X),Integer) :- to_integer(X,OInteger), Integer is OInteger + 1. + +not_prime_i(I,Comp) :- + Comp*Comp < I+1, + (I mod Comp =:= 0; I mod (Comp + 2) =:= 0; + not_prime_i(I,Comp+6)). + +prime_i_entry(I) :- + I > 1, (I =:= 2; I =:= 3; + I mod 2 =\= 0, I mod 3 =\= 0, + \+not_prime_i(I, 5)). + + +prime(X) :- to_integer(X,I), prime_i_entry(I). \ No newline at end of file