How Input, Parameters, and Arguments Work in Verse

Input is information added to a program and used by code to make changes.

The function examples given in the previous lesson didn’t need any input:

GetNumberOfMousetrapsYouCanAfford() : int

GetNumberOfMousetrapsYouCanAfford() : int

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You know this because the parentheses () in the function signature above are empty.

Parameters

You can define the input a function needs by adding a parameter to the function signature.

A parameter is a constant that’s declared in the function signature between the parentheses. When a parameter is set, you can use it in the body of the function.

The syntax for a function that includes a parameter looks like this:

|  |  |
| --- | --- |
|  | name(parameter : type) : type = |
|  | codeblock |

name(parameter : type) : type = codeblock

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In the following example, CoinsPerMousetrap is now a parameter for the function BuyMousetrap():

|  |  |
| --- | --- |
|  | var Coins : int = 500 |
|  |  |
|  | BuyMousetrap(CoinsPerMousetrap : int) : void = |
|  | set Coins = Coins - CoinsPerMousetrap |
|  | Print("Mousetrap bought! You have {Coins} coins left.") |