# Lesson 5

# In this lesson, you will learn to use
# variables and conditional statements.

# General Instructions:
#
# This lesson contains two examples and two
# exercises (A, B).
#
# To listen to an example, change "comment"
# to "uncomment" on the "comment do" line,
# then click the "Run" menu command at the
# top of the Sonic Pi editor window.
# When you are done with the example, turn
# it off by changing "uncomment" back to
# "comment," and move on to the next section
# of the lesson.
#

# Variables: In Lesson 4, we saw that code can
# be placed into blocks and repeated. If we
# give values special names (variables), we can
# change those values within the repeated block.

# Example 1 - Variables inside a repeating block

comment do
  use_bpm 100
  myNote =  60
  myTime = 1
  13.times do
    play myNote
    sleep myTime
    myNote = myNote + 1
  end
end

#   Notice that by changing the value of the variable
#   inside the repeating block, we can do useful things
#   like playing a chromatic scale, but with fewer lines
#   of code than if each individual value were assigned
#   on a different line of code.

# Exercise A
#   Change the code in Example 1:
#   1) starting note is :G4
#   2) bpm is 120,
#   3) beat length (myTime) is 1.5 times longer
#   4) block repeats seven times rather than 13
#   5) scale is whole-tone (whole steps)





# Conditionals. You can control the flow of
# a program by checking the value of a variable and
# taking action based on the state of that variable.
# For example, you could increase the value of a
# variable by one until it reaches a certain number,
# and then increase it by two after that.
# To check the value of a variable, you can use the
# "if" conditional. Comparison operators such as
# > (greater than), < (less than), = (equal), >=
# (greater than or equal to), <= (less than or equal to)
# are often used to test a variable's value. The "else"
# conditional can be used to provide alternative
# actions if a variable does not meet a conditional test.


# Example 2 - Conditionals:

comment do
  use_bpm 100
  myNote =  60
  myTime = 1
  13.times do
    play myNote
    sleep myTime
    if myNote < 67
      myNote = myNote + 1
    else
      myNote = myNote + 2
    end
  end
end

# Exercise B:
#   Modify Example 2
#     1) if myNote < 67 # change to if myNote > 65
#     2) myNote = myNote + 1 # change to myNote = myNote - 2
#     3) myNote = myNote + 2 # change to myNote = myNote + 1