Merge pull request #33 from IBM/cleue-mostly-adequate-fp-go

fix: add examples for [Frisby's Mostly Adequate Guide]

README.md

@@ -73,7 +73,7 @@ This library aims to provide a set of data types and functions that make it easy
 
 The library itself also comprises many small functions, but it's admittedly harder to maintain than code that uses it. However this asymmetry is intended because it offloads complexity from users into a central component.
 
-## Comparation to Idiomatic Go
+## Comparison to Idiomatic Go
 
 In this section we discuss how the functional APIs differ from idiomatic go function signatures and how to convert back and forth.
 
@@ -181,7 +181,7 @@ The `Map` operation for `ReaderIOEither` is defined as:
 func Map[R, E, A, B any](f func(A) B) func(fa ReaderIOEither[R, E, A]) ReaderIOEither[R, E, B]
 ```
 
-and in fact the equivalent operations for all other mondas follow the same pattern, we could try to introduce a new type for `ReaderIOEither` (without a parameter) as a HKT, e.g. like so (made-up syntax, does not work in go):
+and in fact the equivalent operations for all other monads follow the same pattern, we could try to introduce a new type for `ReaderIOEither` (without a parameter) as a HKT, e.g. like so (made-up syntax, does not work in go):
 
 ```go
 func Map[HKT, R, E, A, B any](f func(A) B) func(HKT[R, E, A]) HKT[R, E, B]

function/cache.go

@@ -0,0 +1,30 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package function
+
+import (
+	G "github.com/IBM/fp-go/function/generic"
+)
+
+// Cache converts a unary function into a unary function that caches the value depending on the parameter
+func Cache[K comparable, T any](f func(K) T) func(K) T {
+	return G.Cache(f)
+}
+
+// ContramapCache converts a unary function into a unary function that caches the value depending on the parameter
+func ContramapCache[A any, K comparable, T any](kf func(A) K) func(func(A) T) func(A) T {
+	return G.ContramapCache[func(A) T](kf)
+}

function/cache_test.go

@@ -0,0 +1,50 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package function
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCache(t *testing.T) {
+	var count int
+
+	withSideEffect := func(n int) int {
+		count++
+		return n
+	}
+
+	cached := Cache(withSideEffect)
+
+	assert.Equal(t, 0, count)
+
+	assert.Equal(t, 10, cached(10))
+	assert.Equal(t, 1, count)
+
+	assert.Equal(t, 10, cached(10))
+	assert.Equal(t, 1, count)
+
+	assert.Equal(t, 20, cached(20))
+	assert.Equal(t, 2, count)
+
+	assert.Equal(t, 20, cached(20))
+	assert.Equal(t, 2, count)
+
+	assert.Equal(t, 10, cached(10))
+	assert.Equal(t, 2, count)
+}

function/generic/cache.go

@@ -0,0 +1,65 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package generic
+
+import (
+	"sync"
+
+	L "github.com/IBM/fp-go/internal/lazy"
+)
+
+// Cache converts a unary function into a unary function that caches the value depending on the parameter
+func Cache[F ~func(K) T, K comparable, T any](f F) F {
+	return ContramapCache[F](func(k K) K { return k })(f)
+}
+
+// ContramapCache converts a unary function into a unary function that caches the value depending on the parameter
+func ContramapCache[F ~func(A) T, KF func(A) K, A any, K comparable, T any](kf KF) func(F) F {
+	return CacheCallback[F](kf, getOrCreate[K, T]())
+}
+
+// getOrCreate is a naive implementation of a cache, without bounds
+func getOrCreate[K comparable, T any]() func(K, func() func() T) func() T {
+	cache := make(map[K]func() T)
+	var l sync.Mutex
+
+	return func(k K, cb func() func() T) func() T {
+		// only lock to access a lazy accessor to the value
+		l.Lock()
+		existing, ok := cache[k]
+		if !ok {
+			existing = cb()
+			cache[k] = existing
+		}
+		l.Unlock()
+		// compute the value outside of the lock
+		return existing
+	}
+}
+
+// CacheCallback converts a unary function into a unary function that caches the value depending on the parameter
+func CacheCallback[F ~func(A) T, KF func(A) K, C ~func(K, func() func() T) func() T, A any, K comparable, T any](kf KF, getOrCreate C) func(F) F {
+	return func(f F) F {
+		return func(a A) T {
+			// cache entry
+			return getOrCreate(kf(a), func() func() T {
+				return L.Memoize[func() T](func() T {
+					return f(a)
+				})
+			})()
+		}
+	}
+}

internal/lazy/memoize.go

@@ -0,0 +1,34 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package lazy
+
+import "sync"
+
+// Memoize computes the value of the provided IO monad lazily but exactly once
+func Memoize[GA ~func() A, A any](ma GA) GA {
+	// synchronization primitives
+	var once sync.Once
+	var result A
+	// callback
+	gen := func() {
+		result = ma()
+	}
+	// returns our memoized wrapper
+	return func() A {
+		once.Do(gen)
+		return result
+	}
+}

io/generic/io.go

@@ -16,11 +16,11 @@
 package generic
 
 import (
-	"sync"
 	"time"
 
 	F "github.com/IBM/fp-go/function"
 	C "github.com/IBM/fp-go/internal/chain"
+	L "github.com/IBM/fp-go/internal/lazy"
 )
 
 // type IO[A any] = func() A
@@ -119,18 +119,7 @@ func Flatten[GA ~func() A, GAA ~func() GA, A any](mma GAA) GA {
 
 // Memoize computes the value of the provided IO monad lazily but exactly once
 func Memoize[GA ~func() A, A any](ma GA) GA {
-	// synchronization primitives
-	var once sync.Once
-	var result A
-	// callback
-	gen := func() {
-		result = ma()
-	}
-	// returns our memoized wrapper
-	return func() A {
-		once.Do(gen)
-		return result
-	}
+	return L.Memoize[GA, A](ma)
 }
 
 // Delay creates an operation that passes in the value after some delay

lazy/lazy.go

@@ -83,7 +83,7 @@ func Flatten[A any](mma Lazy[Lazy[A]]) Lazy[A] {
 	return G.Flatten(mma)
 }
 
-// Memoize computes the value of the provided IO monad lazily but exactly once
+// Memoize computes the value of the provided [Lazy] monad lazily but exactly once
 func Memoize[A any](ma Lazy[A]) Lazy[A] {
 	return G.Memoize(ma)
 }

number/integer/string.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package integer
+
+import "strconv"
+
+var (
+	// ToString converts an integer to a string
+	ToString = strconv.Itoa
+)

ord/ord.go

@@ -131,9 +131,7 @@ func FromStrictCompare[A C.Ordered]() Ord[A] {
 	return MakeOrd(strictCompare[A], strictEq[A])
 }
 
-/**
- * Test whether one value is _strictly less than_ another
- */
+// Lt tests whether one value is _strictly less than_ another
 func Lt[A any](O Ord[A]) func(A) func(A) bool {
 	return func(second A) func(A) bool {
 		return func(first A) bool {
@@ -142,9 +140,7 @@ func Lt[A any](O Ord[A]) func(A) func(A) bool {
 	}
 }
 
-/**
- * Test whether one value is less or equal than_ another
- */
+// Leq Tests whether one value is less or equal than_ another
 func Leq[A any](O Ord[A]) func(A) func(A) bool {
 	return func(second A) func(A) bool {
 		return func(first A) bool {
@@ -156,7 +152,7 @@ func Leq[A any](O Ord[A]) func(A) func(A) bool {
 /**
  * Test whether one value is _strictly greater than_ another
  */
-func Gt[A any](O Ord[A]) func(A) func(A) bool {
+func cc[A any](O Ord[A]) func(A) func(A) bool {
 	return func(second A) func(A) bool {
 		return func(first A) bool {
 			return O.Compare(first, second) > 0
@@ -164,9 +160,7 @@ func Gt[A any](O Ord[A]) func(A) func(A) bool {
 	}
 }
 
-/**
- * Test whether one value is greater or equal than_ another
- */
+// Geq tests whether one value is greater or equal than_ another
 func Geq[A any](O Ord[A]) func(A) func(A) bool {
 	return func(second A) func(A) bool {
 		return func(first A) bool {

samples/mostly-adequate/README.md

@@ -0,0 +1,6 @@
+# Mostly Adequate: fp-go Companion Guide
+
+This resource is meant to serve as a go "companion" resource to Professor [Frisby's Mostly Adequate Guide](https://github.com/MostlyAdequate/mostly-adequate-guide).  
+
+It is a port of the [mostly-adequate-fp-ts](https://github.com/ChuckJonas/mostly-adequate-fp-ts/) book.
+

samples/mostly-adequate/chapter01_test.go

@@ -0,0 +1,47 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mostlyadequate
+
+import "fmt"
+
+type Flock struct {
+	Seagulls int
+}
+
+func MakeFlock(n int) Flock {
+	return Flock{Seagulls: n}
+}
+
+func (f *Flock) Conjoin(other *Flock) *Flock {
+	f.Seagulls += other.Seagulls
+	return f
+}
+
+func (f *Flock) Breed(other *Flock) *Flock {
+	f.Seagulls = f.Seagulls * other.Seagulls
+	return f
+}
+
+func Example_flock() {
+
+	flockA := MakeFlock(4)
+	flockB := MakeFlock(2)
+	flockC := MakeFlock(0)
+
+	fmt.Println(flockA.Conjoin(&flockC).Breed(&flockB).Conjoin(flockA.Breed(&flockB)).Seagulls)
+
+	// Output: 32
+}

samples/mostly-adequate/chapter04_currying_test.go

@@ -0,0 +1,46 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mostlyadequate
+
+import (
+	"regexp"
+	"strings"
+
+	F "github.com/IBM/fp-go/function"
+	N "github.com/IBM/fp-go/number"
+	I "github.com/IBM/fp-go/number/integer"
+	S "github.com/IBM/fp-go/string"
+)
+
+var (
+	Match = F.Curry2((*regexp.Regexp).FindStringSubmatch)
+	Split = F.Curry2(F.Bind3of3((*regexp.Regexp).Split)(-1))
+
+	Add      = N.Add[int]
+	ToString = I.ToString
+	ToLower  = strings.ToLower
+	ToUpper  = strings.ToUpper
+	Concat   = F.Curry2(S.Monoid.Concat)
+)
+
+// Replace cannot be generated via [F.Curry3] because the order of parameters does not match our desired curried order
+func Replace(search *regexp.Regexp) func(replace string) func(s string) string {
+	return func(replace string) func(s string) string {
+		return func(s string) string {
+			return search.ReplaceAllString(s, replace)
+		}
+	}
+}

samples/mostly-adequate/chapter05_composing_test.go

@@ -0,0 +1,60 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mostlyadequate
+
+import (
+	"fmt"
+	"regexp"
+
+	A "github.com/IBM/fp-go/array"
+	F "github.com/IBM/fp-go/function"
+	S "github.com/IBM/fp-go/string"
+)
+
+var (
+	Exclaim   = S.Format[string]("%s!")
+	Shout     = F.Flow2(ToUpper, Exclaim)
+	Dasherize = F.Flow4(
+		Replace(regexp.MustCompile(`\s{2,}`))(" "),
+		Split(regexp.MustCompile(` `)),
+		A.Map(ToLower),
+		A.Intercalate(S.Monoid)("-"),
+	)
+)
+
+func Example_shout() {
+	fmt.Println(Shout("send in the clowns"))
+
+	// Output: SEND IN THE CLOWNS!
+}
+
+func Example_dasherize() {
+	fmt.Println(Dasherize("The world is a vampire"))
+
+	// Output: the-world-is-a-vampire
+}
+
+func Example_pipe() {
+	output := F.Pipe2(
+		"send in the clowns",
+		ToUpper,
+		Exclaim,
+	)
+
+	fmt.Println(output)
+
+	// Output: SEND IN THE CLOWNS!
+}

samples/mostly-adequate/chapter08_tupperware_test.go

@@ -0,0 +1,133 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mostlyadequate
+
+import (
+	"fmt"
+	"time"
+
+	E "github.com/IBM/fp-go/either"
+	"github.com/IBM/fp-go/errors"
+	F "github.com/IBM/fp-go/function"
+	N "github.com/IBM/fp-go/number"
+	O "github.com/IBM/fp-go/option"
+	"github.com/IBM/fp-go/ord"
+	S "github.com/IBM/fp-go/string"
+)
+
+type Account struct {
+	Balance float32
+}
+
+func MakeAccount(b float32) Account {
+	return Account{Balance: b}
+}
+
+func getBalance(a Account) float32 {
+	return a.Balance
+}
+
+var (
+	ordFloat32       = ord.FromStrictCompare[float32]()
+	UpdateLedger     = F.Identity[Account]
+	RemainingBalance = F.Flow2(
+		getBalance,
+		S.Format[float32]("Your balance is $%0.2f"),
+	)
+	FinishTransaction = F.Flow2(
+		UpdateLedger,
+		RemainingBalance,
+	)
+	getTwenty = F.Flow2(
+		Withdraw(20),
+		O.Fold(F.Constant("You're broke!"), FinishTransaction),
+	)
+)
+
+func Withdraw(amount float32) func(account Account) O.Option[Account] {
+
+	return F.Flow3(
+		getBalance,
+		O.FromPredicate(ord.Geq(ordFloat32)(amount)),
+		O.Map(F.Flow2(
+			N.Add(-amount),
+			MakeAccount,
+		)))
+}
+
+type User struct {
+	BirthDate string
+}
+
+func getBirthDate(u User) string {
+	return u.BirthDate
+}
+
+func MakeUser(d string) User {
+	return User{BirthDate: d}
+}
+
+var parseDate = F.Bind1of2(E.Eitherize2(time.Parse))(time.DateOnly)
+
+func GetAge(now time.Time) func(User) E.Either[error, float64] {
+	return F.Flow3(
+		getBirthDate,
+		parseDate,
+		E.Map[error](F.Flow3(
+			now.Sub,
+			time.Duration.Hours,
+			N.Mul(1/24.0),
+		)),
+	)
+}
+
+func Example_widthdraw() {
+	fmt.Println(getTwenty(MakeAccount(200)))
+	fmt.Println(getTwenty(MakeAccount(10)))
+
+	// Output:
+	// Your balance is $180.00
+	// You're broke!
+}
+
+func Example_getAge() {
+	now, err := time.Parse(time.DateOnly, "2023-09-01")
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(GetAge(now)(MakeUser("2005-12-12")))
+	fmt.Println(GetAge(now)(MakeUser("July 4, 2001")))
+
+	fortune := F.Flow3(
+		N.Add(365.0),
+		S.Format[float64]("%0.0f"),
+		Concat("If you survive, you will be "),
+	)
+
+	zoltar := F.Flow3(
+		GetAge(now),
+		E.Map[error](fortune),
+		E.GetOrElse(errors.ToString),
+	)
+
+	fmt.Println(zoltar(MakeUser("2005-12-12")))
+
+	// Output:
+	// Right[<nil>, float64](6472)
+	// Left[*time.ParseError, float64](parsing time "July 4, 2001" as "2006-01-02": cannot parse "July 4, 2001" as "2006")
+	// If you survive, you will be 6837
+}

samples/mostly-adequate/chapter09_monadiconions_test.go

@@ -0,0 +1,64 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mostlyadequate
+
+import (
+	"fmt"
+
+	A "github.com/IBM/fp-go/array"
+	F "github.com/IBM/fp-go/function"
+	O "github.com/IBM/fp-go/option"
+)
+
+type (
+	Street struct {
+		Name   string
+		Number int
+	}
+
+	Address struct {
+		Street   Street
+		Postcode string
+	}
+
+	AddressBook struct {
+		Addresses []Address
+	}
+)
+
+func getAddresses(ab AddressBook) []Address {
+	return ab.Addresses
+}
+
+func getStreet(s Address) Street {
+	return s.Street
+}
+
+var FirstAddressStreet = F.Flow3(
+	getAddresses,
+	A.Head[Address],
+	O.Map(getStreet),
+)
+
+func Example_street() {
+	s := FirstAddressStreet(AddressBook{
+		Addresses: A.From(Address{Street: Street{Name: "Mulburry", Number: 8402}, Postcode: "WC2N"}),
+	})
+	fmt.Println(s)
+
+	// Output:
+	// Some[mostlyadequate.Street]({Mulburry 8402})
+}

samples/mostly-adequate/doc.go

@@ -0,0 +1,19 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package mostlyadequate is meant to serve as a go "companion" resource to Professor [Frisby's Mostly Adequate Guide].
+//
+// [Frisby's Mostly Adequate Guide]: https://github.com/MostlyAdequate/mostly-adequate-guide
+package mostlyadequate