RosettaCodeData/Task/Nth-root/XPL0/nth-root.xpl0

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include c:\cxpl\stdlib;
func real NRoot(A, N); \Return the Nth root of A
real A, N;
real X, X0, Y;
int I;
[X:= 1.0; \initial guess
repeat X0:= X;
Y:= 1.0;
for I:= 1 to fix(N)-1 do Y:= Y*X0;
X:= ((N-1.0)*X0 + A/Y) / N;
until abs(X-X0) < 1.0E-15; \(until X=X0 doesn't always work)
return X;
];
[Format(5, 15);
RlOut(0, NRoot( 2., 2.)); CrLf(0);
RlOut(0, Power( 2., 0.5)); CrLf(0); \for comparison
RlOut(0, NRoot(27., 3.)); CrLf(0);
RlOut(0, NRoot(1024.,10.)); CrLf(0);
]