From the course: ReasonML: First Look

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Creating your own data types

Creating your own data types - ReasonML Tutorial

From the course: ReasonML: First Look

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Creating your own data types

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- [Instructor] Remember this code that we developer earlier to find the price of a cake given its size? Everything works great if we have a valid string like half, but an invalid string like small gives us a price of zero. Let's run this program to show that. We can prevent this sort of error, giving invalid strings, by creating a datatype for cake sizes that allows only valid choices. In this file, caketype.re, we're going to define a type named cakeSize. Type names must begin with lowercase. And then preceded by vertical bars, we give the values that tell how to construct a cake size type. It can be either full or half or quarter. These values must begin with an uppercase letter. Now that we have a constructor for the datatype, we combined values of that type to variables. For example I can let cake1 equal half. If I try to use an invalid value such as small I get an error right away that says unbound constructor.…

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