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comparison scripts/specfun/nthroot.m @ 19326:238522618904

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nthroot.m: Fix division by zero warning when input x is 0 (bug #43492). * nthroot.m: Check whether input is a scalar 0, and don't apply integer correction to calculated root as this leads to a division by zero. Add BIST test for bug.
author Rik <rik@octave.org>
date Wed, 29 Oct 2014 08:21:24 -0700
parents a4c226a963c5
children 4197fc428c7d
comparison
equal deleted inserted replaced
19325:64f034147e9a 19326:238522618904
72 else 72 else
73 y = x .^ (1/n); 73 y = x .^ (1/n);
74 endif 74 endif
75 75
76 if (integer_n && n > 0 && isfinite (n)) 76 if (integer_n && n > 0 && isfinite (n))
77 ## FIXME: What is this correction for? 77 if (isscalar (y) && y == 0)
78 y = ((n-1)*y + x ./ (y.^(n-1))) / n; 78 ## Don't apply correction which leads to division by zero (bug #43492)
79 y = merge (isfinite (y), y, x); 79 else
80 ## FIXME: What is this correction for?
81 y = ((n-1)*y + x ./ (y.^(n-1))) / n;
82 y = merge (isfinite (y), y, x);
83 endif
80 endif 84 endif
81
82 endif 85 endif
83 86
84 endfunction 87 endfunction
85 88
86 89
88 %!assert (nthroot (81, 4), 3) 91 %!assert (nthroot (81, 4), 3)
89 %!assert (nthroot (Inf, 4), Inf) 92 %!assert (nthroot (Inf, 4), Inf)
90 %!assert (nthroot (-Inf, 7), -Inf) 93 %!assert (nthroot (-Inf, 7), -Inf)
91 %!assert (nthroot (-Inf, -7), 0) 94 %!assert (nthroot (-Inf, -7), 0)
92 95
96 ## Bug #43492. This should not generate a division by zero warning
97 %!test
98 %! warnmsg = lastwarn ();
99 %! assert (nthroot (0, 2), 0);
100 %! assert (lastwarn (), warnmsg);
101
93 %% Test input validation 102 %% Test input validation
94 %!error nthroot () 103 %!error nthroot ()
95 %!error nthroot (1) 104 %!error nthroot (1)
96 %!error nthroot (1,2,3) 105 %!error nthroot (1,2,3)
97 %!error <X must not contain complex values> nthroot (1+j, 2) 106 %!error <X must not contain complex values> nthroot (1+j, 2)