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RealSign

Sign function (WMA link)

RealSign[x]

returns -1, 0 or 1 depending on whether x is negative,
zero or positive.

RealSign is also known as sgn or signum function.

• • RealSign[-3.]

RealSign[z] is left unevaluated for complex z:

• • RealSign[2. + 3. I]

• • D[RealSign[x^2],x]

• • Integrate[RealSign[u],{u,0,x}]