6.59.5 Testing if a variable is in an expression: has
The has command determines whether or not an expression
contains a variable.
-
has takes two arguments:
-
expr, an expression.
- x, the name of a variable.
- has(expr,x) returns 0 if
expr doesn’t contain x, otherwise it returns an integer
giving the position of x on lname(expr)
(where the position starts at 1).
Examples.
-
Input:
has(x*y*sin(x),y)
Output:
- Input:
has(x*y*sin(x),z)
Output: