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5.3 Conditionals
# Conditionals
A common thing you'll likely find yourself wanting to do is to not only
play a random note (see the previous section on randomness) but also
make a random decision and based on the outcome run some code or some
other code. For example, you might want to randomly play a drum or a
cymbal. We can achieve this with an `if` statement.
## Flipping a Coin
So, let's flip a coin: if it's heads, play a drum, if it's tails, play a
cymbal. Easy. We can emulate a coin flip with our `one_in` function
(introduced in the section on randomness) specifying a probability of 1
in 2: `one_in(2)`. We can then use the result of this to decide between
two pieces of code, the code to play the drum and the code to play the
cymbal:
```
loop do
if one_in(2)
sample :drum_heavy_kick
else
sample :drum_cymbal_closed
end
sleep 0.5
end
```
Notice that `if` statements have three parts:
* The question to ask
* The first choice of code to run (if the answer to the question is yes)
* The second choice of code to run (if the answer to the question is no)
Typically in programming languages, the notion of yes is represented by
the term `true` and the notion of no is represented by the term
`false`. So we need to find a question that will give us a `true` or
`false` answer which is exactly what `one_in` does.
Notice how the first choice is wrapped between the `if` and the `else`
and the second choice is wrapped between the `else` and the `end`. Just
like do/end blocks you can put multiple lines of code in either
place. For example:
```
loop do
if one_in(2)
sample :drum_heavy_kick
sleep 0.5
else
sample :drum_cymbal_closed
sleep 0.25
end
end
```
This time we're sleeping for a different amount of time depending on
which choice we make.
## Simple if
Sometimes you want to optionally execute just one line of code. This is
possible by placing `if` and then the question at the end. For example:
```
use_synth :dsaw
loop do
play 50, amp: 0.3, release: 2
play 53, amp: 0.3, release: 2 if one_in(2)
play 57, amp: 0.3, release: 2 if one_in(3)
play 60, amp: 0.3, release: 2 if one_in(4)
sleep 1.5
end
```
This will play chords of different numbers with the chance of each note
playing having a different probability.
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