The effect! Macro — Do-Notation for Mortals

Chapter 2 introduced the effect! macro as “syntactic sugar for flat_map.” That’s technically accurate, but undersells it. In practice, effect! is how you write almost every multi-step computation in effectful.

This chapter covers the why, the how, and the limits of the macro. By the end you’ll be fluent in bind*, comfortable handling errors inside the macro, and clear on when not to use it.