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fix: make a distinction between Chain and Compose for endomorphism

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Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>
This commit is contained in:
Dr. Carsten Leue
2025-11-12 13:51:00 +01:00
parent 311ed55f06
commit 567315a31c
5 changed files with 325 additions and 95 deletions
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46
v2/endomorphism/doc.go
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@@ -39,13 +39,18 @@
// double := func(x int) int { return x * 2 }
// increment := func(x int) int { return x + 1 }
//
// // Compose them
// doubleAndIncrement := endomorphism.Compose(double, increment)
// result := doubleAndIncrement(5) // (5 * 2) + 1 = 11
// // Compose them (RIGHT-TO-LEFT execution)
// composed := endomorphism.Compose(double, increment)
// result := composed(5) // increment(5) then double: (5 + 1) * 2 = 12
//
// // Chain them (LEFT-TO-RIGHT execution)
// chained := endomorphism.MonadChain(double, increment)
// result2 := chained(5) // double(5) then increment: (5 * 2) + 1 = 11
//
// # Monoid Operations
//
// Endomorphisms form a monoid, which means you can combine multiple endomorphisms:
// Endomorphisms form a monoid, which means you can combine multiple endomorphisms.
// The monoid uses Compose, which executes RIGHT-TO-LEFT:
//
// import (
// "github.com/IBM/fp-go/v2/endomorphism"
@@ -55,22 +60,39 @@
// // Get the monoid for int endomorphisms
// monoid := endomorphism.Monoid[int]()
//
// // Combine multiple endomorphisms
// // Combine multiple endomorphisms (RIGHT-TO-LEFT execution)
// combined := M.ConcatAll(monoid)(
// func(x int) int { return x * 2 },
// func(x int) int { return x + 1 },
// func(x int) int { return x * 3 },
// func(x int) int { return x * 2 }, // applied third
// func(x int) int { return x + 1 }, // applied second
// func(x int) int { return x * 3 }, // applied first
// )
// result := combined(5) // ((5 * 2) + 1) * 3 = 33
// result := combined(5) // (5 * 3) = 15, (15 + 1) = 16, (16 * 2) = 32
//
// # Monad Operations
//
// The package also provides monadic operations for endomorphisms:
// The package also provides monadic operations for endomorphisms.
// MonadChain executes LEFT-TO-RIGHT, unlike Compose:
//
// // Chain allows sequencing of endomorphisms
// // Chain allows sequencing of endomorphisms (LEFT-TO-RIGHT)
// f := func(x int) int { return x * 2 }
// g := func(x int) int { return x + 1 }
// chained := endomorphism.MonadChain(f, g)
// chained := endomorphism.MonadChain(f, g) // f first, then g
// result := chained(5) // (5 * 2) + 1 = 11
//
// # Compose vs Chain
//
// The key difference between Compose and Chain/MonadChain is execution order:
//
// double := func(x int) int { return x * 2 }
// increment := func(x int) int { return x + 1 }
//
// // Compose: RIGHT-TO-LEFT (mathematical composition)
// composed := endomorphism.Compose(double, increment)
// result1 := composed(5) // increment(5) * 2 = (5 + 1) * 2 = 12
//
// // MonadChain: LEFT-TO-RIGHT (sequential application)
// chained := endomorphism.MonadChain(double, increment)
// result2 := chained(5) // double(5) + 1 = (5 * 2) + 1 = 11
//
// # Type Safety
//