An identifier is used in the context of a function while it doesn't denote a valid function. Example:
z = sim(z) ; "sim" is not a valid function
If sim is meant to serve as a user-defined (parameter) function, put a @ sign before it. Otherwise, change its name to a valid function.
z = @sim(z) z = sin(z)
Note: the oldz function can only be used in the final section of coloring algorithms. Otherwise, this error is raised.
See Also
Errors