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Free algebra

As explained in Functional Programming in Scala, Second Edition

A free algebra is an algebraic representation of effect operations whose programs are interpreted separately into an executable effect.

A free algebra represents primitive effect operations as a program that can be sequenced without committing to a target effect. An interpreter later translates that program into an executable effect, separating program construction from execution. section 13.6

This separation contrasts with capability traits: a capability constructs operations directly in the target monad, while a free program is built first and interpreted afterward. The Free data type supplies sequencing before any concrete effect is chosen. section 13.6

How Functional Programming in Scala, Second Edition covers it

How deep it goes
Defines deferred interpretation and sequencing, but stops short of showing the Free data type or an interpreter implementation.
Examples
Contrasts Free programs with Console capabilities using greeting and file-concatenation programs.
What it assumes
Assumes familiarity with target monads and monadic sequencing through flatMap.
What you can do after
Evaluate/understand how deferred interpretation separates effect descriptions from executable effects.
How it connects
Connects free algebra with interpreters, target monads, sequencing, and capability traits.
Cover of Functional Programming in Scala, Second Edition
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This explainer was generated by Manning's knowledge graph from the text of Functional Programming in Scala, Second Edition. The section links point to the parts of the book it draws on.