Make invalid states representable.

We should model the state of a system using algebraic types and include states that are invalid.

Apr 25, 2023

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A favorite functional programming motto is “make invalid states representable.” If we can fully model the possible states of a system using algebraic types—including states that are invalid—then we can provide good error messages that describe why something is invalid, and we have more possibilities for recovering from error.

A datatype: Configuration

For…

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