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We've managed to get our calculator to work. But in this lesson, I want to talk about something else.

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I want to talk about the difference between printing something to the console over here versus returning

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something as an output from a function, because a lot of students get very confused at this stage and

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they think, well, why don't I just print this results instead of returning it?

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What's the actual difference and why would I use return?

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That's what I want to address in this lesson.

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At the moment, we've got these four functions, and when we call it, we pass over some inputs and

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then once we get a hold of the output, we go ahead and print it out into the console.

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Now, in the current state of the calculator, it's hard to see the difference between the print and

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the return.

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But here's a question.

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What if we wanted to take the output that comes from calling this function and instead of just storing

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it inside a variable and then printing it out, what if we want to pass it as an input to another function?

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Let's say that at this point we decided, you know what, we're going to ask them to pick another operation.

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And then let's ask them to pick another number.

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And finally, let's go ahead and get the calculation function again based on this new operation symbol

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that they picked. And then we're going to calculate the new answer

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but this time, instead of passing over the calculation function, we're going to pass over the answer

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that we got back from this step.

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So num1 is now the previous answer

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and the second number that's going to be the input is going to be num3.

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At this point, when we're calling this calculation function, we're passing over the results or outputs

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of this calculation function, and that is going in right here,

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and then the third number goes in as the second input.

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What basically has happened here is I've taken the output from this function,

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so in fact, I could replace this answer with this output,

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and I've taken that as the first input into the calculation function and then num3 as the second

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input

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and then using all of this in order to get the answer.

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Let's call this first_answer,

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and let's call this second_answer just to differentiate the two answers.

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And now I'm going to write a slightly different print statement. In this case, the calculation is done

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using the first_answer and then the operation symbol and then the num3 that was inserted at

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this point in order to obtain the second_answer.

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So now if we give this a run.

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Let's do 3 + 2. Now, in this first step of the calculation, we get 5 as the result.

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So now if I want to pick another operation, let's I want to multiply 5 by 3.

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Then I'm going to take this 5, which is the previous answer,

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I'm going to say multiply, and then I'm going to provide the next number, which we'll call 3.

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And now it takes the previous answer from the last step and puts that in as the first number in the

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calculation, multiplies it by 3 in order to get the final answer.

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In this case, what I'm able to do because I have an output from my calculation function up here because

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each of these all return their answer, I'm able to take the result from that calculation and plug it

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right back into another calculation function using the result of that function call as the input to

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another function call.

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And I'm only able to do this because I'm using the return statement and because I have outputs from

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my functions.

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This would not be possible if I was using a print statement.

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In the next lesson, we're going to reorganize our code and introduce a while loop so that we can continue

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making as many calculations as we want to.