Lauren fp ts exercises

src/exo0 - Composing with pipe and flow/exo0.exercise.ts

@@ -24,7 +24,8 @@
 // - `flow(f) === f`
 // - `pipe(x, f) === f(x)`
 
-import { unimplemented } from '../utils';
+import { pipe, flow } from 'fp-ts/lib/function';
+// import { unimplemented } from '../utils';
 
 export const isEven = (value: number) => value % 2 === 0;
 
@@ -42,9 +43,9 @@ export const not = (value: boolean) => !value;
 // `pipe` or `flow`), write the function `isOdd` that checks if a number is
 // odd.
 
-export const isOddP: (value: number) => boolean = unimplemented;
+export const isOddP = (value: number)  => pipe(value, isEven, not);
 
-export const isOddF: (value: number) => boolean = unimplemented;
+export const isOddF: (value: number) => boolean = flow(isEven, not);
 
 // We will write a function that for any given number, computes the next
 // one according to the following rules:
@@ -63,10 +64,10 @@ export const ifThenElse =
 // Using `pipe` and `ifThenElse`, write the function that computes the next step in the Collatz
 // sequence.
 
-export const next: (value: number) => number = unimplemented;
+export const next = (value: number) => pipe(value, isOddP, ifThenElse(() => value * 3 + 1, () => value/2));
 
 // Using only `flow` and `next`, write the function that for any given number
 // a_n from the Collatz sequence, returns the number a_n+3 (i.e. the number
 // three steps ahead in the sequence).
 
-export const next3: (value: number) => number = unimplemented;
+export const next3: (value: number) => number = flow(next, next, next);

src/exo1 - Basic types/exo1.exercise.ts

@@ -4,10 +4,9 @@
 // - Either
 // - TaskEither
 
-import { Either } from 'fp-ts/Either';
 import { Option } from 'fp-ts/Option';
-import { TaskEither } from 'fp-ts/TaskEither';
-import { unimplemented, sleep, unimplementedAsync } from '../utils';
+import { sleep } from '../utils';
+import { either, option, taskEither } from 'fp-ts';
 
 export const divide = (a: number, b: number): number => {
   return a / b;
@@ -25,7 +24,23 @@ export const divide = (a: number, b: number): number => {
 // - `option.none`
 
 export const safeDivide: (a: number, b: number) => Option<number> =
-  unimplemented;
+  (a: number, b: number) => {
+    if (b !== 0) {
+      return option.some(divide(a, b))
+    }
+    return option.none
+}
+
+/*
+I used the solution to help me write the version below:
+
+const isValidDivisor = (n: number): boolean => n !== 0;
+export const safeDivide = (a: number, b: number) => 
+  pipe(b,
+    option.fromPredicate(b => isValidDivisor(b)), 
+    option.map(b => divide(a, b))
+  )
+*/
 
 // You probably wrote `safeDivide` using `if` statements, and it's perfectly valid!
 // There are ways to not use `if` statements.
@@ -54,11 +69,11 @@ export const safeDivide: (a: number, b: number) => Option<number> =
 // Here is a simple error type to help you:
 export type DivisionByZeroError = 'Error: Division by zero';
 export const DivisionByZero = 'Error: Division by zero' as const;
-
-export const safeDivideWithError: (
+ 
+export const safeDivideWithError = (
   a: number,
-  b: number,
-) => Either<DivisionByZeroError, number> = unimplemented;
+  b: number) =>  b === 0 ? either.left(DivisionByZero) :
+    either.right(divide(a, b));
 
 ///////////////////////////////////////////////////////////////////////////////
 //                                TASKEITHER                                 //
@@ -83,7 +98,7 @@ export const asyncDivide = async (a: number, b: number) => {
 // a TaskEither<Error, T>:
 // - `taskEither.tryCatch(f: () => promise, onReject: reason => leftValue)`
 
-export const asyncSafeDivideWithError: (
+export const asyncSafeDivideWithError = (
   a: number,
   b: number,
-) => TaskEither<DivisionByZeroError, number> = unimplementedAsync;
+) => taskEither.tryCatch(() => asyncDivide(a, b), () => DivisionByZero)

src/exo2 - Combinators/exo2.exercise.ts

@@ -4,7 +4,8 @@
 import { Either } from 'fp-ts/Either';
 import { Option } from 'fp-ts/Option';
 import { Failure } from '../Failure';
-import { unimplemented } from '../utils';
+import { flow, pipe } from 'fp-ts/lib/function';
+import { either, option, readonlyArray } from 'fp-ts';
 
 ///////////////////////////////////////////////////////////////////////////////
 //                                   SETUP                                   //
@@ -117,17 +118,64 @@ export const invalidAttackerFailure = Failure.builder(
 // common operations done with the `Either` type and it is available through
 // the `flatMap` operator.
 
-export const checkAttackerAndSmash: (
-  attacker: Option<Character>,
-) => Either<NoAttackerFailure | InvalidAttackerFailure, Damage> = unimplemented;
 
-export const checkAttackerAndBurn: (
-  attacker: Option<Character>,
-) => Either<NoAttackerFailure | InvalidAttackerFailure, Damage> = unimplemented;
 
-export const checkAttackerAndShoot: (
-  attacker: Option<Character>,
-) => Either<NoAttackerFailure | InvalidAttackerFailure, Damage> = unimplemented;
+//****** I looked at the solution to get help on this one. **********//
+
+const isAttackerDefined = 
+    either.fromOption(() => 
+    noAttackerFailure("No attacker currently selected"));
+
+const isAllowedWarriorAction =
+  either.fromPredicate(isWarrior, target => 
+    invalidAttackerFailure(`${target.toString()} cannot perform smash`));
+
+const isAllowedWizardAction =
+  either.fromPredicate(isWizard, target => 
+    invalidAttackerFailure(`${target.toString()} cannot perform burn`));
+
+const isAllowedArcherAction =
+  either.fromPredicate(isArcher, target => 
+    invalidAttackerFailure(`${target.toString()} cannot perform shoot`));
+
+const smash = flow (
+  isAllowedWarriorAction,
+  either.map(attacker => attacker.smash())  
+)
+
+const burn = flow (
+  isAllowedWizardAction,
+  either.map(attacker => attacker.burn())
+)
+
+const shoot = flow (
+  isAllowedArcherAction,
+  either.map( attacker => attacker.shoot())
+)
+
+export const checkAttackerAndSmash = (
+  target: Option<Character>,
+): Either<NoAttackerFailure | InvalidAttackerFailure, Damage> => pipe(
+  target,
+  isAttackerDefined,
+  either.flatMap(smash)  
+)
+
+export const checkAttackerAndBurn = (
+  target: Option<Character>,
+): Either<NoAttackerFailure | InvalidAttackerFailure, Damage> => pipe(
+  target,
+  isAttackerDefined,
+  either.flatMap(burn)
+);
+
+export const checkAttackerAndShoot = (
+  target: Option<Character>,
+): Either<NoAttackerFailure | InvalidAttackerFailure, Damage> => pipe (
+  target,
+  isAttackerDefined,
+  either.flatMap(shoot)
+);
 
 ///////////////////////////////////////////////////////////////////////////////
 //                                  OPTION                                   //
@@ -146,14 +194,26 @@ export const checkAttackerAndShoot: (
 // BONUS POINTS: If you properly defined small private helpers in the previous
 // section, they should be easily reused for those use-cases.
 
-export const smashOption: (character: Character) => Option<Damage> =
-  unimplemented;
-
-export const burnOption: (character: Character) => Option<Damage> =
-  unimplemented;
-
-export const shootOption: (character: Character) => Option<Damage> =
-  unimplemented;
+export const smashOption = (character: Character): Option<Damage> =>
+  pipe (
+    character,
+    smash,
+    option.fromEither
+  );
+
+export const burnOption = (character: Character) => 
+  pipe (
+    character, 
+    burn,
+    option.fromEither
+  );
+
+export const shootOption = (character: Character) =>
+  pipe (
+    character,
+    shoot,
+    option.fromEither
+  );
 
 ///////////////////////////////////////////////////////////////////////////////
 //                                   ARRAY                                   //
@@ -168,11 +228,39 @@ export const shootOption: (character: Character) => Option<Damage> =
 // perform mapping and filtering at the same time by applying a function
 // of type `A => Option<B>` over the collection.
 
+
+
+
+//****** I looked at the solution to get help on this one. **********//
+
 export interface TotalDamage {
   [Damage.Physical]: number;
   [Damage.Magical]: number;
   [Damage.Ranged]: number;
 }
+/*
+Why doesn't the code in the line below work as a replacement for option 1 on line 252?
+    readonlyArray.filterMap(flow(option.filter(isWizard), option.map(character => character))),
+*/
+
+export const attack = (army: ReadonlyArray<Character>) => ({
+[Damage.Physical]:  
+  pipe (
+    army,
+    readonlyArray.filterMap(smashOption),
+    readonlyArray.size,
+  ),
+  [Damage.Magical]:  
+  pipe (
+    army,
+    readonlyArray.filterMap(burnOption),
+    readonlyArray.size,
+  ),
+  [Damage.Ranged]:  
+  pipe (
+    army,
+    readonlyArray.filterMap(shootOption),
+    readonlyArray.size,
+  ),
+})
 
-export const attack: (army: ReadonlyArray<Character>) => TotalDamage =
-  unimplemented;

src/exo3 - Sort with Ord/exo3.exercise.ts

@@ -2,7 +2,14 @@
 // Sort things out with `Ord`
 
 import { Option } from 'fp-ts/Option';
-import { unimplemented } from '../utils';
+import { number, option, ord, readonlyArray, string } from 'fp-ts';
+import { pipe } from 'fp-ts/lib/function';
+
+
+
+/******* I relied heavily on the fp-ts-cheatsheet to solve these problems **********/
+
+
 
 // Have you ever looked at the methods provided by `fp-ts` own `Array` and
 // `ReadonlyArray` modules? They expose a load of functions to manipulate
@@ -34,13 +41,19 @@ import { unimplemented } from '../utils';
 // expose some pre constructed instances of `Ord<T>` for said primitives such as
 // `string.Ord: Ord<string>` or `number.Ord: Ord<number>`.
 
-export const sortStrings: (
+export const sortStrings = (
   strings: ReadonlyArray<string>,
-) => ReadonlyArray<string> = unimplemented;
+): ReadonlyArray<string>  => pipe(
+  strings,
+  readonlyArray.sort(string.Ord)
+);
 
-export const sortNumbers: (
+export const sortNumbers = (
   numbers: ReadonlyArray<number>,
-) => ReadonlyArray<number> = unimplemented;
+): ReadonlyArray<number> => pipe (
+  numbers,
+  readonlyArray.sort(number.Ord)
+);
 
 ///////////////////////////////////////////////////////////////////////////////
 //                                REVERSE SORT                               //
@@ -55,9 +68,12 @@ export const sortNumbers: (
 //
 // HINT: Any ordering can be reversed with a simple function `ord.reverse`.
 
-export const sortNumbersDescending: (
+export const sortNumbersDescending = (
   numbers: ReadonlyArray<number>,
-) => ReadonlyArray<number> = unimplemented;
+): ReadonlyArray<number> => pipe (
+  numbers,
+  readonlyArray.sort(ord.reverse(number.Ord))
+);
 
 ///////////////////////////////////////////////////////////////////////////////
 //                            SORT OPTIONAL VALUES                           //
@@ -73,9 +89,12 @@ export const sortNumbersDescending: (
 // of building an `Ord` instance for their qualified inner type. You may want
 // to take a look at `option.getOrd`.
 
-export const sortOptionalNumbers: (
+export const sortOptionalNumbers = (
   optionalNumbers: ReadonlyArray<Option<number>>,
-) => ReadonlyArray<Option<number>> = unimplemented;
+): ReadonlyArray<Option<number>> => pipe (
+  optionalNumbers,
+  readonlyArray.sort(option.getOrd(number.Ord))
+);
 
 ///////////////////////////////////////////////////////////////////////////////
 //                           SORT COMPLEX OBJECTS                            //
@@ -99,13 +118,25 @@ export interface Person {
   readonly age: Option<number>;
 }
 
-export const sortPersonsByName: (
+export const sortPersonsByName = (
   persons: ReadonlyArray<Person>,
-) => ReadonlyArray<Person> = unimplemented;
-
-export const sortPersonsByAge: (
+): ReadonlyArray<Person>  => pipe (
+  persons,
+  readonlyArray.sortBy([pipe(
+    string.Ord,
+    ord.contramap((person: Person) => person.name)
+  )])
+);
+
+export const sortPersonsByAge = (
   persons: ReadonlyArray<Person>,
-) => ReadonlyArray<Person> = unimplemented;
+): ReadonlyArray<Person> => pipe (
+  persons,
+  readonlyArray.sortBy( [pipe (
+    option.getOrd(number.Ord),
+    ord.contramap((person: Person) => person.age)
+  )])
+);
 
 ///////////////////////////////////////////////////////////////////////////////
 //                          COMBINE SORTING SCHEMES                          //
@@ -116,6 +147,19 @@ export const sortPersonsByAge: (
 //
 // HINT: Take a look at `readonlyArray.sortBy`
 
-export const sortPersonsByAgeThenByName: (
+const byAge = pipe (
+  option.getOrd(number.Ord),
+    ord.contramap((person: Person) => person.age)
+)
+
+const byName = pipe (
+  string.Ord,
+    ord.contramap((person: Person) => person.name)
+)
+
+export const sortPersonsByAgeThenByName = (
   persons: ReadonlyArray<Person>,
-) => ReadonlyArray<Person> = unimplemented;
+): ReadonlyArray<Person> => pipe (
+  persons,
+  readonlyArray.sortBy([byAge, byName])
+);