Gapplet

You input a polynomial f Z[x,y]. We then view it as the recipee for a binary operation on Z, mapping (a,b) Z×Z to f(a,b) Z, and we analyse whether the operation is associative.

Input a polynomial f in x, y with integral coefficients, 
e.g., x*y+x+y.
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Test whether the corresponding binary map is associative
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We compute f(x,f(y,z)) and f(f(x,y),z), and compare the two. By arguments as in Lagrange interpolation, equality of these two polynomials in x, y, z is equivalent to associativity.
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