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Task/Modular-arithmetic/Red/modular-arithmetic.red

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+Red ["Modular arithmetic"]
+
+; defining the modular integer class, and a constructor
+modulus: 13
+m: function [n] [
+	either object? n [make n []] [context [val: n % modulus]]
+]
+; redefining operators +, -, *, / to include modular integers
+foreach [op fun][+ add - subtract * multiply / divide][
+	set op make op! function [a b] compose/deep [
+		either any [object? a object? b][
+			a: m a
+			b: m b
+			m (fun) a/val b/val
+		][(fun) a b]	
+	]
+]
+; redefining power - ** ; second operand must be an integer
+**: make op! function [a n] [
+	either object? a [
+		tmp: 1
+		loop n [tmp: tmp * a/val % modulus]
+		m tmp
+	][power a n]	
+]
+; testing
+f: function [x] [x ** 100 + x + 1]
+print ["f definition is:" mold :f]
+print ["f((integer) 10) is:" f 10]
+print ["f((modular) 10) is: (modular)" f m 10]