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Ensurance

Why is ensurance needed?

Although the type system had already prevented a lot of value errors, there are still cases where invalid value can still be passed in to some functions.

Thus, Pineapple have a built-in feature called Ensurance to allow you to make sure that invalid value is not passed in into certain function.

Fun Fact

In another languages like C, Java or Python, ensurance is also known as assertion.

How to use ensurance?

To use ensurance, just use the ensure keyword.

For example,

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def (this Number).divide(that Number) -> Number
    ensure that != 0
    // performs division

Then, suppose we have the following program,

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def .main
    let y = 4.divide(0)

When we run the program, we will get the following error message:

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Ensurance failed:                         

        at  .divide  [example.pine:16:11]            

           > |   16 |     ensure that != 0      
             |      |            ~~~~~~~~~      



        at  .main  [example.pine:1:12]              

           > |    1 |     let y = 4.divide(0)   
             |      |             ~~~~~~~~~~~

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