The Torsion(C, t) calling sequence computes the torsion of the curve , which must have exactly three components, that is, the curve that this Vector represents must be in .

The curve  can be specified as a Vector or as a Vector-valued procedure. If  is a procedure, the returned object is a procedure. Otherwise, the returned object is an expression.

If  is not specified, the function tries to determine a suitable variable name from the components of .  To do this, it checks all of the indeterminates of type name in the components of  and removes the ones that are determined to be constants.

If the resulting set has a single entry, the single entry is the variable name.  If it has more than one entry, an error is raised.

If a coordinate system attribute is specified on ,  is interpreted in this coordinate system.  Otherwise, the curve is interpreted as a curve in the current default coordinate system. If the curve and the coordinate system are incompatible, an error is returned.