# Revision history [back]

You should be more careful about "expressions" and "functions".

An expression is something like this

var('u,v')
ex = u*cos(v)


A function is something like this

cool(u,v) = u+v


One possible way to go : use only functions, and call them with arguments always :

good(u, v) = cool(u, v) + u - v


Your "right_curve_u" is an expression. Make it a function.