Hey All-

I just started attempting to program in Ruby a month ago, but have reached 
an impasse.

I am writing a dosing program and am trying to do something very simple: 
Have a user enter either m for a male or f for a female so that info can be 
taken to the next equation to be used for something else.

I originally wrote it as follows:

#Introduction

puts 'Hello. Welcome to the Aminoglycoside Dosing Calculator.'
# Determines the patient dosing gender

puts 'What gender is your patient? Please enter m or f'
        ptSexS = gets.chomp.downcase
        if ptSexS == 'f'
                doseSexS = 'female'
        elsif ptSexS == 'm'
                doseSexS = 'male'
        end
puts 'Your patient is a ' + doseSexS


The problem here is I have written all of the mathematical operations I need 
in blocks like this, but I dont know how to make them accomodate for invalid 
answers.
For instance, if the user enters an m or an f above, I have the doseSexS 
determined for the next part of the program. If the user enters something 
else, I want it to ay "please try again' and start over..

I have tried while loops but cant get it to work as well as making it into a 
method. Is there a different way to do this that my lack of experience is 
preventingme from seeing/ Is iteration over a an array something worth 
following? I apologize for such a basic question, but the PickAxe,the book 
by Chris Pine, and multiple web sites are failing me and I am turnig here as 
a last resort...

Thanks in advance for any help

Matthew F Borgeson