doc: document how to use a request builder for http

Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>

context/readerioeither/http/request_test.go

@@ -21,6 +21,13 @@ import (
 	"testing"
 
 	H "net/http"
+
+	R "github.com/IBM/fp-go/context/readerioeither"
+	E "github.com/IBM/fp-go/either"
+	"github.com/IBM/fp-go/errors"
+	F "github.com/IBM/fp-go/function"
+	IOE "github.com/IBM/fp-go/ioeither"
+	"github.com/stretchr/testify/assert"
 )
 
 type PostItem struct {
@@ -30,6 +37,47 @@ type PostItem struct {
 	Body   string `json:"body"`
 }
 
+func getTitle(item PostItem) string {
+	return item.Title
+}
+
+type simpleRequestBuilder struct {
+	method  string
+	url     string
+	headers H.Header
+}
+
+func requestBuilder() simpleRequestBuilder {
+	return simpleRequestBuilder{method: "GET"}
+}
+
+func (b simpleRequestBuilder) WithURL(url string) simpleRequestBuilder {
+	b.url = url
+	return b
+}
+
+func (b simpleRequestBuilder) WithHeader(key, value string) simpleRequestBuilder {
+	if b.headers == nil {
+		b.headers = make(H.Header)
+	} else {
+		b.headers = b.headers.Clone()
+	}
+	b.headers.Set(key, value)
+	return b
+}
+
+func (b simpleRequestBuilder) Build() R.ReaderIOEither[*H.Request] {
+	return func(ctx context.Context) IOE.IOEither[error, *H.Request] {
+		return IOE.TryCatchError(func() (*H.Request, error) {
+			req, err := H.NewRequestWithContext(ctx, b.method, b.url, nil)
+			if err == nil {
+				req.Header = b.headers
+			}
+			return req, err
+		})
+	}
+}
+
 func TestSendSingleRequest(t *testing.T) {
 
 	client := MakeClient(H.DefaultClient)
@@ -40,7 +88,70 @@ func TestSendSingleRequest(t *testing.T) {
 
 	resp1 := readItem(req1)
 
-	resE := resp1(context.Background())()
+	resE := resp1(context.TODO())()
 
 	fmt.Println(resE)
 }
+
+// setHeaderUnsafe updates a header value in a request object by mutating the request object
+func setHeaderUnsafe(key, value string) func(*H.Request) *H.Request {
+	return func(req *H.Request) *H.Request {
+		req.Header.Set(key, value)
+		return req
+	}
+}
+
+func TestSendSingleRequestWithHeaderUnsafe(t *testing.T) {
+
+	client := MakeClient(H.DefaultClient)
+
+	// this is not safe from a puristic perspective, because the map call mutates the request object
+	req1 := F.Pipe2(
+		"https://jsonplaceholder.typicode.com/posts/1",
+		MakeGetRequest,
+		R.Map(setHeaderUnsafe("Content-Type", "text/html")),
+	)
+
+	readItem := ReadJson[PostItem](client)
+
+	resp1 := F.Pipe2(
+		req1,
+		readItem,
+		R.Map(getTitle),
+	)
+
+	res := F.Pipe1(
+		resp1(context.TODO())(),
+		E.GetOrElse(errors.ToString),
+	)
+
+	assert.Equal(t, "sunt aut facere repellat provident occaecati excepturi optio reprehenderit", res)
+}
+
+func TestSendSingleRequestWithHeaderSafe(t *testing.T) {
+
+	client := MakeClient(H.DefaultClient)
+
+	// the request builder assembles config values to construct
+	// the final http request. Each `With` step creates a copy of the settings
+	// so the flow is pure
+	request := requestBuilder().
+		WithURL("https://jsonplaceholder.typicode.com/posts/1").
+		WithHeader("Content-Type", "text/html").
+		Build()
+
+	readItem := ReadJson[PostItem](client)
+
+	response := F.Pipe2(
+		request,
+		readItem,
+		R.Map(getTitle),
+	)
+
+	res := F.Pipe1(
+		response(context.TODO())(),
+		E.GetOrElse(errors.ToString),
+	)
+
+	assert.Equal(t, "sunt aut facere repellat provident occaecati excepturi optio reprehenderit", res)
+}

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