Tutorial Sgn定義は誤りだろう。

Tutorial Sgn定義は誤りだろう。
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CSint *Sgn(CSint *vint)
{
int n = 0;
int array[3];
CSint *s;
if (cs_getMin(vint) < 0)
array[n++] = -1;
if (cs_getMax(vint) > 0)
array[n++] = 1;
if (cs_isIn(vint, 1))
array[n++] = 0;
s = cs_createCSintFromDomain(array, n);
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if (cs_isIn(vint, 1)) <----- if (cs_isIn(vint, 0))
array[n++] = 0;