Exercise 6.

Write a Maple procedure called structure that when given a Maple expression returns the structure of the expression as a tree, namely

• for atomic objects (integers and strings) just return the object
• otherwise, return a list with the type of the object as the first element, and the remaining elements the structure of the operands of the object.

For example: structure(x^3*sin(x)/cos(x)); should return

    [*, [^, x, 3], [function, sin, x], [^, [function, cos, x], -1]]

Your routine should handle the Maple types integer, fraction, float, `+`, `*`, `^`, string, indexed, function, range, equation, set, list, series and table. Test your function on the following input

   Int( exp(-t)*sqrt(t)*ln(t), t=0..infinity ) =
   int( exp(-t)*sqrt(t)*ln(t), t=0..infinity );