Class 9 Lecture Notes
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The document outlines class 9's agenda focused on flow control and loops in Ruby programming. It covers concepts such as iterating through loops using different structures (while-end, until-end, for-end) and discusses methods for defining and calling functions. The session includes exercises and examples for practical application and sets the stage for the upcoming lesson on arrays.
Class 9 Lecture Notes
- 1. Class 9 – Flow Control: Loops
- 2. Agenda Warm-up, Issues Controlling Flow with loops Quest: Defining and calling a Ruby method Assignment 6 Mid-term Exam
- 3. Warm-up and Issues Lateral Thinking Exercise Project Issues? Other Issues? Remaining Activities/ Work Plan Dates
- 4. Flow Control: Looping Iteration refers to the ability to repeat similar actions conditionally rather than requiring a user-entered signal to stop. Iterations may be loops using “while-end” or “until-end” or “for-end” or may be an array method using “.each” We will examine only loops tonight and save the “each” method for next week when we cover arrays.
- 5. Looping Scenarios Score Averager – what if you don’t know how many students there will be? A persistent converter
- 6. Looping Notation Pseudocode (sample) # get the number of rounds to complete # set a counter to value 0 # while the counter is less than the number of rounds # do some stuff here # increase the counter # end the loop
- 7. Looping Flowchart The Loop Decision implicit May evaluate true or false condition May use a counter to advance value start end Assignment name? Set counter = 0 Counter>10? Calculate Average Print Average Increment Counter Student Grade? Yes No
- 8. Looping Ruby Code While-end (a condition is true at the outset) var_type=“any wine” while var_type!=“exit” puts “what type of wine do you like (type exit to end)” var_type=gets.chomp puts ”Mmmmm. I like ” + var_type + “,too!” end
- 9. Looping Ruby Code Until-end (condition is false at the outset) var_type=“any wine” until var_type==“exit” puts “what type of wine do you like (type exit to end)” var_type=gets.chomp puts ”Mmmmm. I like ” + var_type + “,too!” end
- 10. Looping Ruby Code For-end (uses a range of values) for i in (1..12) puts i.to_s + “ o\’clock and all is well” end for x in (“man”..”max”) puts x end
- 11. Exercise Sample: Can I do it until I wear glasses? Instructions: Develop a loop that will ask user to tell something about himself/herself Respond to each prompt in some way, e.g. “Interesting! Tell me more!” Continue to loop until the user says “I wear glasses” Then say “Bye!” and end program
- 12. Quest: Defining and Calling a Method What is a method? A function or operation that may be used several times in the application May perform a calculation on variables May return a value Must be at top of file in Ruby Why? Shortened code, consistent results Single code block to edit
- 13. Ruby: Declare/ Call Method Example def doFtoC (fVal) temp=fVal*9/5 + 32 return temp.round(2) end puts “enter fahrenheit temp” f_temp=gets.chomp.to_f puts “Celsius =” + doFtoC(f_temp).to_s
- 14. One last example Ruby – the wine connoisseur Your turn: Assignment 6 From Flowchart to Flow Control
- 15. Wrap-up Summary Iteration – repeating functions/operations Loops – a kind of iteration Methods: while, until, for Next Week Arrays, Intro Project 2 Assignment 6 due at start of class