cs102 lab3

cs102 lab3

http://www.maths.nuigalway.ie/~gettrick/teach/cs102/labs/l3.html

For this lab you must submit all source code (python files), and, if applicable, the result(s) of running the program on (a few) test cases. This should be sent in via BLACKBOARD (not directly by email). The source code must be well presented (indenting, spaces, reasonable variable/function names, etc.) and must include comments (as a rough guideline - aim to have nearly as many comments as lines of code). Any questions asked should be answered by typing into a plain text (.txt) file which should also be uploaded via blackboard.
This material should be uploaded before the deadline of 5pm Friday February 11th, 2011. You will lose 20% for each day (or part of day) the lab is late.
Plagiarism (the unattributed copying of work from other sources (internet, fellow students,....)) will not be tolerated. Please see http://www.nuigalway.ie/engineering/documents/plagiarism_guide_students _v4.pdf. You risk getting zero for your lab if it is found to be plagiarized.

This week, you are asked to write solutions in PYTHON using recursive functions.

Write a program in PYTHON to calculate the double factorial of a Natural Number input by the user. The double factorial of n (written as n!!) is n(n-2)(n-4)... so for example 7!! = (7)(5)(3)(1) = 105 while 6!! = (6)(4)(2) = 48. Your program must use a recursive function. (Be careful of the two different base cases for n even or odd).

For a certain application, the user must choose a password that has no vowels. Write a program that reads in from the user (use raw_input) a possible password, and checks that it matches this requirement. You must use a recursive function. (Hint: Your function can take as input a string. Then it checks the first letter. If that letter is not a vowel, let the function call itself, with as input the string minus the first letter (use a slice!). If the first letter is a vowel, return some constant from the function (e.g. 1). If the input string to the function is NULL, return some other constant (e.g. 0). Then in your main program, use the returned value to print out something meaningful to the user.)