Hedy - Slides

Welcome to level 15!

Remember Functions?

Too much code?

### Too much code?

The code below has a lot of repetition.
                    
                    <iframe class="fragment" src="/render_code/15?code=print%20%28%27This%20code%20will%20calculate%20the%20first%205%20squares%20and%20print%20the%20result.%27%29%0A%0Asquare1%20%3D%201%2A1%0Aprint%20%28%27the%20square%20of%201%20%3D%27%2C%20square1%29%0Asquare2%20%3D%202%2A2%0Aprint%20%28%27the%20square%20of%202%20%3D%20%27%2C%20square2%29%0Asquare3%20%3D%203%2A3%0Aprint%20%28%27the%20square%20of%203%20%3D%20%27%2C%20square3%29%0Asquare4%20%3D%204%2A4%0Aprint%20%28%27the%20square%20of%204%20%3D%20%27%2C%20square4%29%0Asquare5%20%3D%205%2A5%0Aprint%20%28%27the%20square%20of%205%20%3D%20%27%2C%20square5%29"></iframe>
                    
                    
                    <aside class="notes">Show the code to your students. Do they see all the repetition?
Ask them if they can come up with a way of writing this code with less lines.
They will probably not be able to figure out a way, so show them the next slide!</aside>

Use a function!

### Use a function!

Now we will try to have the same output with less lines of code.
For this we write a function: a piece of code we can repeat multiple times with different input.
                    
                    <iframe class="fragment" src="/render_code/15?code=def%20calculate_square%28number%29%3A%0A%20%20%20%20square%20%3D%20number%2Anumber%0A%20%20%20%20print%20%28%27the%20square%20of%27%2C%20number%2C%20%27%3D%27%2C%20square%29%0A%0Aprint%20%28%27This%20code%20will%20calculate%20the%20first%205%20squares%20and%20print%20the%20result.%27%29%0A%0Acalculate_square%281%29%0Acalculate_square%282%29%0Acalculate_square%283%29%0Acalculate_square%284%29%0Acalculate_square%285%29"></iframe>
                    
                    
                    <aside class="notes">Run the code. Make sure your students see how this output comes from the code.
Now we only have two lines less than in the last slide.

Explain to your students that the more repetition you have the better it is to use functions.
Some benefits: Less code, so more organized code and the writing of the code will go quicker.
Less possibility to make mistakes and easier to find them if you make them.

Show that you can change something in the function, such that all the output changes.</aside>

Functions with more arguments

### Functions with more arguments

The input that is in the brackets of a function we call the argument.
You can use multiple arguments for one function:
                    
                    <iframe class="fragment" src="/render_code/15?code=def%20fairy_tale%28princess%2C%20prince%2C%20something_poisonous%2C%20expression_of_love%29%0Aanswer%20%3D%20input%28%27Do%20you%20want%20me%20to%20tell%20you%20a%20fairy%20tale%3F%27%29%0Aif%20answer%20%3D%3D%20yes%3A%0A%20%20%20%20print%20%28%27Once%20upon%20a%20time%20there%20was%20a%20girl%20named%20%27%2C%20princess%29%0A%20%20%20%20print%20%28%27She%20ate%20some%20%27%2C%20something_poisonous%2C%20%27%20and%20nearly%20died...%27%29%0A%20%20%20%20print%20%28%27But%20prince%20%27%2C%20prince%2C%20%27%20came%20to%20visit%20her%20and%20gave%20her%20a%20%27%2C%20expression_of_love%20%29%0A%20%20%20%20print%20%28%27This%20healed%20%27%2C%20princess%20%27%20and%20she%20fell%20in%20love%20with%20%27%2C%20prince%29%0A%20%20%20%20print%20%28princess%2C%20%27%20and%20%27%2C%20prince%2C%20%27%20lived%20happily%20ever%20after.%27%29%0Aelse%3A%0A%20%20%20%20print%20%28%27No%20problem.%20Perhaps%20next%20time.%27%29%0A%0Afairy_tale%28%27Snowwhite%27%2C%20%27Casper%27%2C%20%27poison%27%2C%20%27kiss%27%29"></iframe>
                    
                    
                    <aside class="notes">Run the code and show that you can change all four arguments to get a different story.</aside>

Return value

### Return value

Sometimes you want to use a number that has been calculated in a function outside a function.
You can use the command `return` to use the value outside of the code.
                    
                    <iframe class="fragment" src="/render_code/15?code=def%20calculate_new_price%28amount%2C%20percentage%29%3A%0A%20%20%20%20percentage%20%3D%20percentage%20/%20100%0A%20%20%20%20discount_amount%20%3D%20amount%20%2A%20percentage%0A%20%20%20%20return%20amount%20-%20discount_amount%0A%0Aold_price%20%3D%20input%20%28%27How%20much%20is%20on%20the%20price%20tag%3F%27%29%0Adiscount%20%3D%20input%20%28%27What%20percentage%20is%20the%20discount%3F%27%29%0A%0Anew_price%20%3D%20_%20calculate_new_price%28old_price%2C%20discount%29%0Aprint%28%27The%20new%20price%20is%20%27%2C%20new_price%2C%20%27%20dollar%27%29"></iframe>
                    
                    
                    <aside class="notes">Can your students think of any other situations where it would be nice to return a value from a function?</aside>

Debugging

Let's check out the adventures!

Let's review!

Show and tell!

Sneak peek into the next level...