Crosscut

I previously showed you what records could look like. Let's continue today with another important building block, variants:

variant { Integer, Text }

A variant is a type that can be either of multiple values (for now, I'm calling these "cases"). In this example, it could be either a value of type Integer or Text. This is often called a "union" (which seems overly general, like it could just as well apply to any composite type) or an "enum" (which seems overly specific), or in programming language theory terms, a sum type.

Like records, variants are structurally typed and anonymous (by default; more on that later). They are also always tagged, which means that what the case of a specific value is, is stored as part of that value. If you encounter a value of the variant type from above, you could figure out what it contains at runtime, via pattern matching.