isPositive(): test whether a number exceeds zero

isPositive(x) returns true when x is strictly greater than zero. It is useful for dimensions, rates, denominators, and quantities that cannot be negative.

Zero is separate

isPositive(0) is false. If zero is allowed, test it separately with isZero(). Use isNegative() for the opposite sign and sign() when you need the three-way result.

Validation

Confirm the value is usable with isFinite() and isNumeric() before applying it to log() or a division. Use a tolerance for values calculated in floating point.