8a0a9fe · ikoHSE/sc-lectures

git.iko.soy/ikoHSE/sc-lectures

Update 🥳

commit8a0a9fe47a72506401e6da16853b673d0515ae59 authoriko <ilyakooo0@gmail.com> dateMon 18 May 2020, 00:03 (6 years ago) parent29262f6

2 files changed+220−180

compare with master

unifiedsplit

3.html+164−148 3.md+56−32

3.html+164−148

@@ -277,7 +277,7 @@

277277<div class="sourceCode" id="cb33"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb33-1"></a>instance Monad WithLog where

278278<a href="#cb33-2"></a> (<=<) f g x = WithLog x3 (log1 <> log2)

279279<a href="#cb33-3"></a> where

280−<a href="#cb33-4"></a> (WithLog x2 log1) = g x1

280+<a href="#cb33-4"></a> (WithLog x2 log1) = g x

281281<a href="#cb33-5"></a> (WithLog x3 log2) = f x2</code></pre></div>

282282</section>

283283<section class="slide level2">

@@ -304,8 +304,8 @@

304304<div class="sourceCode" id="cb40"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb40-1"></a>(>>=) :: Monad m => m b -> (b -> m c) -> m c</code></pre></div>

305305<div class="sourceCode" id="cb41"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb41-1"></a>buyCoffee :: Order -> Maybe Payment

306306<a href="#cb41-2"></a>buyCoffee order = getCoffee order >>= payForCoffee</code></pre></div>

307−<div class="sourceCode" id="cb42"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb42-1"></a>maybeBuyCoffee :: Myabe Order -> Maybe Payment

308−<a href="#cb42-2"></a>maybeBuyCoffee order = order >>= buyCoffee</code></pre></div>

307+<div class="sourceCode" id="cb42"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb42-1"></a>maybeBuyCoffee :: Maybe Order -> Maybe Payment

308+<a href="#cb42-2"></a>maybeBuyCoffee mOrder = mOrder >>= buyCoffee</code></pre></div>

309309<div class="sourceCode" id="cb43"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb43-1"></a>(>>=) :: Monad m => m b -> (b -> m c) -> m c</code></pre></div>

310310<div class="sourceCode" id="cb44"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb44-1"></a>(>=>) :: Monad m => (a -> m b) -> (b -> m c) -> (a -> m c)</code></pre></div>

311311<div class="sourceCode" id="cb45"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb45-1"></a> (() -> m b) -> (b -> m c) -> (() -> m c)</code></pre></div>

@@ -315,13 +315,13 @@

315315

316316<div class="sourceCode" id="cb47"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb47-1"></a>(>=>) :: Monad m => (a -> m b) -> (b -> m c) -> (a -> m c)</code></pre></div>

317317<div class="sourceCode" id="cb48"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb48-1"></a>(>>=) :: Monad m => m b -> (b -> m c) -> m c

318−<a href="#cb48-2"></a>(>>=) mb f = ( (\() -> mb) >=> f ) ()</code></pre></div>

319−<div class="sourceCode" id="cb49"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb49-1"></a>(>>=) mb f = ( (\() -> mb) >=> f ) ()

320−<a href="#cb49-2"></a>-- () -> m b |

321−<a href="#cb49-3"></a>-- b -> m c

318+<a href="#cb48-2"></a>(>>=) mb bmc = ( (\() -> mb) >=> bmc ) ()</code></pre></div>

319+<div class="sourceCode" id="cb49"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb49-1"></a>(>>=) mb bmc = ( (\() -> mb) >=> bmc ) ()

320+<a href="#cb49-2"></a>-- () -> m b |

321+<a href="#cb49-3"></a>-- b -> m c

322322<a href="#cb49-4"></a>--

323−<a href="#cb49-5"></a>-- ^-------------------^

324−<a href="#cb49-6"></a>-- () -> m c</code></pre></div>

323+<a href="#cb49-5"></a>-- ^-----------------------^

324+<a href="#cb49-6"></a>-- () -> m c</code></pre></div>

325325</section>

326326<section class="slide level2">

327327

@@ -375,24 +375,22 @@

375375<a href="#cb58-2"></a> { runReader :: r -> a

376376<a href="#cb58-3"></a> }</code></pre></div>

377377<code>r</code> – то, что у нас в “окружении”.

378−<div class="sourceCode" id="cb59"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb59-1"></a>getCoffee :: Order -> Reader Markup Coffee

379−<a href="#cb59-2"></a>payForCoffee :: Coffee -> Reader Markup Payment</code></pre></div>

380−<div class="sourceCode" id="cb60"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb60-1"></a>payment :: Payment

381−<a href="#cb60-2"></a>payment = runReader (payForCoffee coffee) markup</code></pre></div>

382378</section>

383379<section class="slide level2">

384380

385−<div class="sourceCode" id="cb61"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb61-1"></a>data Reader r a = Reader { runReader :: r -> a }

386−<a href="#cb61-2"></a>

387−<a href="#cb61-3"></a>getCoffee :: Order -> Reader Markup Coffee

388−<a href="#cb61-4"></a>payForCoffee :: Coffee -> Reader Markup Payment</code></pre></div>

389−<div class="sourceCode" id="cb62"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb62-1"></a>buyCoffee :: Order -> Reader Markup Payment

390−<a href="#cb62-2"></a>buyCoffee = payForCoffee <=< getCoffee</code></pre></div>

391−<div class="sourceCode" id="cb63"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb63-1"></a>type PricingEnv = Reader Markup</code></pre></div>

392−<div class="sourceCode" id="cb64"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb64-1"></a>getCoffee :: Order -> PricingEnv Coffee

393−<a href="#cb64-2"></a>payForCoffee :: Coffee -> PricingEnv Payment

394−<a href="#cb64-3"></a>buyCoffee :: Order -> PricingEnv Payment

395−<a href="#cb64-4"></a>buyCoffee = payForCoffee <=< getCoffee</code></pre></div>

381+<div class="sourceCode" id="cb59"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb59-1"></a>data Reader r a = Reader { runReader :: r -> a }

382+<a href="#cb59-2"></a>

383+<a href="#cb59-3"></a>getCoffee :: Order -> Markup -> Coffee

384+<a href="#cb59-4"></a>payForCoffee :: Coffee -> Markup -> Payment</code></pre></div>

385+<div class="sourceCode" id="cb60"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb60-1"></a>getCoffee :: Order -> Reader Markup Coffee

386+<a href="#cb60-2"></a>payForCoffee :: Coffee -> Reader Markup Payment</code></pre></div>

387+<div class="sourceCode" id="cb61"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb61-1"></a>type PricingEnv = Reader Markup</code></pre></div>

388+<div class="sourceCode" id="cb62"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb62-1"></a>getCoffee :: Order -> PricingEnv Coffee

389+<a href="#cb62-2"></a>payForCoffee :: Coffee -> PricingEnv Payment</code></pre></div>

390+<div class="sourceCode" id="cb63"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb63-1"></a>buyCoffee :: Order -> PricingEnv Payment

391+<a href="#cb63-2"></a>buyCoffee = payForCoffee <=< getCoffee</code></pre></div>

392+<div class="sourceCode" id="cb64"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb64-1"></a>payment :: Payment

393+<a href="#cb64-2"></a>payment = runReader (buyCoffee order) markup</code></pre></div>

396394</section>

397395<section class="slide level2">

398396

@@ -445,83 +443,88 @@

445443<a href="#cb69-2"></a>qux :: a -> Reader r b

446444<a href="#cb69-3"></a>

447445<a href="#cb69-4"></a>foo :: Reader r b

448−<a href="#cb69-5"></a>foo = bar >>= \a -> qux a</code></pre></div>

446+<a href="#cb69-5"></a>foo = bar >>= \x -> qux x</code></pre></div>

449447<div class="sourceCode" id="cb70"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb70-1"></a>foo = do

450−<a href="#cb70-2"></a> a <- bar

451−<a href="#cb70-3"></a> qux a</code></pre></div>

448+<a href="#cb70-2"></a> -- (x :: a) <- (bar :: Reader r a)

449+<a href="#cb70-3"></a> x <- bar

450+<a href="#cb70-4"></a> qux x</code></pre></div>

452451<div class="sourceCode" id="cb71"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb71-1"></a>foo = do

453−<a href="#cb71-2"></a> a <- bar

454−<a href="#cb71-3"></a> b <- qux a

455−<a href="#cb71-4"></a> return b</code></pre></div>

452+<a href="#cb71-2"></a> -- (x :: a) <- (bar :: Reader r a)

453+<a href="#cb71-3"></a> x <- bar

454+<a href="#cb71-4"></a> -- (y :: b) <- (qux x :: Reader r b)

455+<a href="#cb71-5"></a> y <- qux x

456+<a href="#cb71-6"></a> return y</code></pre></div>

457+<div class="sourceCode" id="cb72"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb72-1"></a>foo = bar >>= \x -> qux x >>= return</code></pre></div>

456458</section>

457459<section class="slide level2">

458460

459−<div class="sourceCode" id="cb72"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb72-1"></a>type PricingEnv = Reader Markup

460−<a href="#cb72-2"></a>

461−<a href="#cb72-3"></a>getCoffeePrice :: Coffee -> PricingEnv Price

462−<a href="#cb72-4"></a>getDiscount :: Coffee -> PricingEnv Price

463−<a href="#cb72-5"></a>getPayment :: Price -> PricingEnv Payment

464−<a href="#cb72-6"></a>

465−<a href="#cb72-7"></a>payForCoffee :: Coffee -> PricingEnv Payment

466−<a href="#cb72-8"></a>payForCoffee coffee =

467−<a href="#cb72-9"></a> coffee >>= getCoffeePrice >>= \coffeePrice ->

468−<a href="#cb72-10"></a> coffee >>= getDiscount >>= \discount ->

469−<a href="#cb72-11"></a> getPayment (coffeePrice - discount)</code></pre></div>

470−<div class="sourceCode" id="cb73"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb73-1"></a>payForCoffee :: Coffee -> PricingEnv Payment

471−<a href="#cb73-2"></a>payForCoffee coffee = do

472−<a href="#cb73-3"></a> coffeePrice <- getCoffeePrice coffee

473−<a href="#cb73-4"></a> discount <- getDiscount coffee

474−<a href="#cb73-5"></a> getPayment (coffeePrice - discount)</code></pre></div>

475−</section>

476−<section id="let-statement" class="slide level2">

477−<h2>Let statement</h2>

478−<div class="sourceCode" id="cb74"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb74-1"></a>payForCoffee :: Coffee -> PricingEnv Payment

461+<div class="sourceCode" id="cb73"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb73-1"></a>type PricingEnv = Reader Markup

462+<a href="#cb73-2"></a>

463+<a href="#cb73-3"></a>getCoffeePrice :: Coffee -> PricingEnv Price

464+<a href="#cb73-4"></a>getDiscount :: Coffee -> PricingEnv Price

465+<a href="#cb73-5"></a>getPayment :: Price -> PricingEnv Payment

466+<a href="#cb73-6"></a>

467+<a href="#cb73-7"></a>payForCoffee :: Coffee -> PricingEnv Payment

468+<a href="#cb73-8"></a>payForCoffee coffee =

469+<a href="#cb73-9"></a> coffee >>= getCoffeePrice >>= \coffeePrice ->

470+<a href="#cb73-10"></a> coffee >>= getDiscount >>= \discount ->

471+<a href="#cb73-11"></a> getPayment (coffeePrice - discount)</code></pre></div>

472+<div class="sourceCode" id="cb74"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb74-1"></a>payForCoffee :: Coffee -> PricingEnv Payment

479473<a href="#cb74-2"></a>payForCoffee coffee = do

480474<a href="#cb74-3"></a> coffeePrice <- getCoffeePrice coffee

481475<a href="#cb74-4"></a> discount <- getDiscount coffee

482476<a href="#cb74-5"></a> getPayment (coffeePrice - discount)</code></pre></div>

483−<div class="sourceCode" id="cb75"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb75-1"></a>payForCoffee :: Coffee -> PricingEnv Payment

477+</section>

478+<section id="let-statement" class="slide level2">

479+<h2>Let statement</h2>

480+<div class="sourceCode" id="cb75"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb75-1"></a>payForCoffee :: Coffee -> PricingEnv Payment

484481<a href="#cb75-2"></a>payForCoffee coffee = do

485482<a href="#cb75-3"></a> coffeePrice <- getCoffeePrice coffee

486483<a href="#cb75-4"></a> discount <- getDiscount coffee

487−<a href="#cb75-5"></a> let amount = coffeePrice - discount

488−<a href="#cb75-6"></a> getPayment amount</code></pre></div>

484+<a href="#cb75-5"></a> getPayment (coffeePrice - discount)</code></pre></div>

485+<div class="sourceCode" id="cb76"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb76-1"></a>payForCoffee :: Coffee -> PricingEnv Payment

486+<a href="#cb76-2"></a>payForCoffee coffee = do

487+<a href="#cb76-3"></a> coffeePrice <- getCoffeePrice coffee

488+<a href="#cb76-4"></a> discount <- getDiscount coffee

489+<a href="#cb76-5"></a> let amount = coffeePrice - discount

490+<a href="#cb76-6"></a> getPayment amount</code></pre></div>

489491</section>

490492<section class="slide level2">

491493

492−<div class="sourceCode" id="cb76"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb76-1"></a>type PricingEnv = Reader Markup

493−<a href="#cb76-2"></a>type Price = Int

494−<a href="#cb76-3"></a>

495−<a href="#cb76-4"></a>data Coffee = Coffee { getCoffeePrice :: Price }

496−<a href="#cb76-5"></a>

497−<a href="#cb76-6"></a>getCoffeePrice :: Coffee -> PricingEnv Price</code></pre></div>

498−<div class="sourceCode" id="cb77"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb77-1"></a>data Reader r a = Reader { runReader :: r -> a}</code></pre></div>

499−<div class="sourceCode" id="cb78"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb78-1"></a>ask :: Reader r r

500−<a href="#cb78-2"></a>ask = Reader (\r -> r)</code></pre></div>

501−<div class="sourceCode" id="cb79"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb79-1"></a>getCoffeePrice :: Coffee -> PricingEnv Price

502−<a href="#cb79-2"></a>getCoffeePrice coffee = do

503−<a href="#cb79-3"></a> markup <- ask

504−<a href="#cb79-4"></a> let coffePrice = getCoffeePrice coffee

505−<a href="#cb79-5"></a> return (coffee + markup)</code></pre></div>

494+<div class="sourceCode" id="cb77"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb77-1"></a>type PricingEnv = Reader Markup

495+<a href="#cb77-2"></a>type Price = Int

496+<a href="#cb77-3"></a>

497+<a href="#cb77-4"></a>data Coffee = Coffee { getCoffeePrice :: Price }

498+<a href="#cb77-5"></a>

499+<a href="#cb77-6"></a>getCoffeePrice :: Coffee -> PricingEnv Price</code></pre></div>

500+<div class="sourceCode" id="cb78"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb78-1"></a>data Reader r a = Reader { runReader :: r -> a}</code></pre></div>

501+<div class="sourceCode" id="cb79"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb79-1"></a>ask :: Reader r r

502+<a href="#cb79-2"></a>ask = Reader (\r -> r)</code></pre></div>

503+<div class="sourceCode" id="cb80"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb80-1"></a>getCoffeePrice :: Coffee -> PricingEnv Price

504+<a href="#cb80-2"></a>getCoffeePrice coffee = do

505+<a href="#cb80-3"></a> -- (markup :: Markup) <- (ask :: PricingEnv Markup)

506+<a href="#cb80-4"></a> markup <- ask

507+<a href="#cb80-5"></a> let coffePrice = getCoffeePrice coffee

508+<a href="#cb80-6"></a> return (coffee + markup)</code></pre></div>

506509</section>

507510<section class="slide level2">

508511

509−<div class="sourceCode" id="cb80"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb80-1"></a>data Order = Order { orderCoffee :: Coffee, orderId :: Int }</code></pre></div>

510−<div class="sourceCode" id="cb81"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb81-1"></a>createOrder :: Coffee -> Order</code></pre></div>

512+<div class="sourceCode" id="cb81"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb81-1"></a>data Order = Order { orderCoffee :: Coffee, orderId :: Int }</code></pre></div>

513+<div class="sourceCode" id="cb82"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb82-1"></a>createOrder :: Coffee -> Order</code></pre></div>

511514Откуда брать <code>orderId</code>?

512−<div class="sourceCode" id="cb82"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb82-1"></a>createOrder :: Coffee -> Reader Int Order

513−<a href="#cb82-2"></a>createOrder coffee = do

514−<a href="#cb82-3"></a> newId <- ask

515−<a href="#cb82-4"></a> return (Order coffee newId)</code></pre></div>

515+<div class="sourceCode" id="cb83"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb83-1"></a>createOrder :: Coffee -> Reader Int Order

516+<a href="#cb83-2"></a>createOrder coffee = do

517+<a href="#cb83-3"></a> newId <- ask

518+<a href="#cb83-4"></a> return (Order coffee newId)</code></pre></div>

516519🎉

517−<div class="sourceCode" id="cb83"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb83-1"></a>createOrders :: [Coffee] -> Reader Int [Order]</code></pre></div>

518−<div class="sourceCode" id="cb84"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb84-1"></a>mapM :: (Monad m) => (a -> m b) -> [a] -> m [b]</code></pre></div>

519−<div class="sourceCode" id="cb85"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb85-1"></a>createOrders = mapM createOrder</code></pre></div>

520+<div class="sourceCode" id="cb84"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb84-1"></a>createOrders :: [Coffee] -> Reader Int [Order]</code></pre></div>

521+<div class="sourceCode" id="cb85"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb85-1"></a>mapM :: (Monad m) => (a -> m b) -> [a] -> m [b]</code></pre></div>

522+<div class="sourceCode" id="cb86"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb86-1"></a>createOrders = mapM createOrder</code></pre></div>

520523</section>

521524<section class="slide level2">

522525

523−<div class="sourceCode" id="cb86"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb86-1"></a>createOrders :: [Coffee] -> Reader Int [Order]

524−<a href="#cb86-2"></a>createOrders = mapM createOrder</code></pre></div>

526+<div class="sourceCode" id="cb87"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb87-1"></a>createOrders :: [Coffee] -> Reader Int [Order]

527+<a href="#cb87-2"></a>createOrders = mapM createOrder</code></pre></div>

525528Все <code>id</code> будут одинаковые.

526529<code>Reader</code> эквивалентно глобальной константе.

527530Айдишники – скорее глобальная переменная.

@@ -530,108 +533,121 @@

530533</section>

531534<section id="state" class="slide level2">

532535<h2>State!</h2>

533−<div class="sourceCode" id="cb87"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb87-1"></a>data State s a = ... -- s -- само состояние

534−<a href="#cb87-2"></a>

535−<a href="#cb87-3"></a>get :: State s s

536−<a href="#cb87-4"></a>put :: s -> State s ()</code></pre></div>

537−<div class="sourceCode" id="cb88"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb88-1"></a>data State s a = State { runState :: s -> (a, s) }

536+<div class="sourceCode" id="cb88"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb88-1"></a>data State s a = ... -- s -- само состояние

538537<a href="#cb88-2"></a>

539538<a href="#cb88-3"></a>get :: State s s

540−<a href="#cb88-4"></a>get = State (\s -> (s, s))

541−<a href="#cb88-5"></a>

542−<a href="#cb88-6"></a>put :: s -> State s ()

543−<a href="#cb88-7"></a>put s = State (\_ -> ((), s))</code></pre></div>

539+<a href="#cb88-4"></a>put :: s -> State s ()</code></pre></div>

540+<div class="sourceCode" id="cb89"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb89-1"></a>data State s a = State { runState :: s -> (a, s) }

541+<a href="#cb89-2"></a>

542+<a href="#cb89-3"></a>get :: State s s

543+<a href="#cb89-4"></a>get = State (\s -> (s, s))

544+<a href="#cb89-5"></a>

545+<a href="#cb89-6"></a>put :: s -> State s ()

546+<a href="#cb89-7"></a>put s = State (\_ -> ((), s))</code></pre></div>

544547</section>

545548<section class="slide level2">

546549

547−<div class="sourceCode" id="cb89"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb89-1"></a>data State s a = State { runState :: s -> (a, s) }</code></pre></div>

548−<div class="sourceCode" id="cb90"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb90-1"></a>class Monad (State s) where

549−<a href="#cb90-2"></a> return x = State (\s -> (x, s))

550−<a href="#cb90-3"></a>

551−<a href="#cb90-4"></a> (>>=) :: State s a -> (a -> State s b) -> State s b

552−<a href="#cb90-5"></a> (State f) >>= g = State go

553−<a href="#cb90-6"></a> where

554−<a href="#cb90-7"></a> go s = runState (g a) s'

555−<a href="#cb90-8"></a> where

556−<a href="#cb90-9"></a> (a, s') = f s</code></pre></div>

550+<div class="sourceCode" id="cb90"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb90-1"></a>data State s a = State { runState :: s -> (a, s) }</code></pre></div>

551+<div class="sourceCode" id="cb91"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb91-1"></a>class Monad (State s) where

552+<a href="#cb91-2"></a> return x = State (\s -> (x, s))

553+<a href="#cb91-3"></a>

554+<a href="#cb91-4"></a> (>>=) :: State s a -> (a -> State s b) -> State s b

555+<a href="#cb91-5"></a> (State f) >>= g = State go

556+<a href="#cb91-6"></a> where

557+<a href="#cb91-7"></a> go s = runState (g a) s'

558+<a href="#cb91-8"></a> where

559+<a href="#cb91-9"></a> (a, s') = f s</code></pre></div>

557560</section>

558561<section class="slide level2">

559562

560563<h3 id="айдишники">Айдишники!</h3>

561−<div class="sourceCode" id="cb91"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb91-1"></a>getNewId :: State Int Int

562−<a href="#cb91-2"></a>getNewId = do

563−<a href="#cb91-3"></a> newId <- get

564−<a href="#cb91-4"></a> put (newId + 1)

565−<a href="#cb91-5"></a> return newId</code></pre></div>

564+<div class="sourceCode" id="cb92"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb92-1"></a>getNewId :: State Int Int

565+<a href="#cb92-2"></a>getNewId = do

566+<a href="#cb92-3"></a> newId <- get

567+<a href="#cb92-4"></a> put (newId + 1)

568+<a href="#cb92-5"></a> return newId</code></pre></div>

566569– Это какой-то процедурный языке получается!

567570– Лучше!*

568−<div class="sourceCode" id="cb92"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb92-1"></a>createOrder :: Coffee -> State Int Order

569−<a href="#cb92-2"></a>createOrder coffee = do

570−<a href="#cb92-3"></a> newId <- getNewId

571−<a href="#cb92-4"></a> return (Order coffee newId)

572−<a href="#cb92-5"></a>

573−<a href="#cb92-6"></a>createOrders :: [Coffee] -> State Int [Order]

574−<a href="#cb92-7"></a>createOrders = mapM createOrder</code></pre></div>

571+<div class="sourceCode" id="cb93"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb93-1"></a>createOrder :: Coffee -> State Int Order

572+<a href="#cb93-2"></a>createOrder coffee = do

573+<a href="#cb93-3"></a> newId <- getNewId

574+<a href="#cb93-4"></a> return (Order coffee newId)

575+<a href="#cb93-5"></a>

576+<a href="#cb93-6"></a>createOrders :: [Coffee] -> State Int [Order]

577+<a href="#cb93-7"></a>createOrders = mapM createOrder</code></pre></div>

575578</section>

576579<section id="еще-монады" class="slide level2">

577580<h2>Еще монады!</h2>

578−<div class="sourceCode" id="cb93"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb93-1"></a>class Monad [] where

579−<a href="#cb93-2"></a> return x = [x]

580−<a href="#cb93-3"></a>

581−<a href="#cb93-4"></a> (>>=) :: [a] -> (a -> [b]) -> [b]

582−<a href="#cb93-5"></a> [] >>= _ = []

583−<a href="#cb93-6"></a> (a : aa) >>= f = f a <> (a >>= f)</code></pre></div>

581+<div class="sourceCode" id="cb94"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb94-1"></a>class Monad [] where

582+<a href="#cb94-2"></a> return x = [x]

583+<a href="#cb94-3"></a>

584+<a href="#cb94-4"></a> (>>=) :: [a] -> (a -> [b]) -> [b]

585+<a href="#cb94-5"></a> [] >>= _ = []

586+<a href="#cb94-6"></a> (a : aa) >>= f = f a <> (a >>= f)</code></pre></div>

584587Контекст недетерменированности (нескольких вариантов)

585−<div class="sourceCode" id="cb94"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb94-1"></a>grid = do

586−<a href="#cb94-2"></a> x <- [1..5]

587−<a href="#cb94-3"></a> y <- [1..5]

588−<a href="#cb94-4"></a> return (x, y)

589−<a href="#cb94-5"></a>

590−<a href="#cb94-6"></a>-- [(1,1),(1,2),(1,3),(1,4),(1,5),(2,1),(2,2),(2,3),(2,4),(2,5),(3,1),(3,2),(3,3),(3,4),(3,5),(4,1),(4,2),(4,3),(4,4),(4,5),(5,1),(5,2),(5,3),(5,4),(5,5)]</code></pre></div>

588+<div class="sourceCode" id="cb95"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb95-1"></a>grid = do

589+<a href="#cb95-2"></a> x <- [1..5]

590+<a href="#cb95-3"></a> y <- [1..5]

591+<a href="#cb95-4"></a> return (x, y)

592+<a href="#cb95-5"></a>

593+<a href="#cb95-6"></a>-- [(1,1),(1,2),(1,3),(1,4),(1,5),(2,1),(2,2),(2,3),(2,4),(2,5),(3,1),(3,2),(3,3),(3,4),(3,5),(4,1),(4,2),(4,3),(4,4),(4,5),(5,1),(5,2),(5,3),(5,4),(5,5)]</code></pre></div>

591594</section>

592595<section class="slide level2">

593596

594597Тривиальная монада

595−<div class="sourceCode" id="cb95"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb95-1"></a>data Identity a = Identity { runIdentity :: a }

596−<a href="#cb95-2"></a>

597−<a href="#cb95-3"></a>class Monad Identity where

598−<a href="#cb95-4"></a> return x = Identity x

599−<a href="#cb95-5"></a>

600−<a href="#cb95-6"></a> (>>=) :: Identity a -> (a -> Identity b) -> Identity b

601−<a href="#cb95-7"></a> (Identity a) >>= f = Identity (f a)</code></pre></div>

598+<div class="sourceCode" id="cb96"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb96-1"></a>data Identity a = Identity { runIdentity :: a }

599+<a href="#cb96-2"></a>

600+<a href="#cb96-3"></a>class Monad Identity where

601+<a href="#cb96-4"></a> return x = Identity x

602+<a href="#cb96-5"></a>

603+<a href="#cb96-6"></a> (>>=) :: Identity a -> (a -> Identity b) -> Identity b

604+<a href="#cb96-7"></a> (Identity a) >>= f = Identity (f a)</code></pre></div>

602605</section>

603606<section class="slide level2">

604607

605−<div class="sourceCode" id="cb96"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb96-1"></a>class Applicative m => Monad m where

606−<a href="#cb96-2"></a> return :: a -> m a

607−<a href="#cb96-3"></a> (>>=) :: m a -> (a -> m b) -> m b</code></pre></div>

608+<div class="sourceCode" id="cb97"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb97-1"></a>class Applicative m => Monad m where

609+<a href="#cb97-2"></a> return :: a -> m a

610+<a href="#cb97-3"></a> (>>=) :: m a -> (a -> m b) -> m b</code></pre></div>

608611Монада – перегрузка композиции функций.

609−<div class="sourceCode" id="cb97"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb97-1"></a>class Functor m => Applicative m where

610−<a href="#cb97-2"></a> pure :: a -> m a

611−<a href="#cb97-3"></a> (<*>) :: m (a -> b) -> m a -> m b</code></pre></div>

612+<div class="sourceCode" id="cb98"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb98-1"></a>class Functor m => Applicative m where

613+<a href="#cb98-2"></a> pure :: a -> m a

614+<a href="#cb98-3"></a> (<*>) :: m (a -> b) -> m a -> m b</code></pre></div>

612615Аппликативный функтор – перегрузка применения функций.

613616– Почему не <code>(a -> b) -> f a -> f b</code>.

614617– Это <code>fmap</code>. (И функции нескольких аргументов)

615618</section>

616619<section class="slide level2">

617620

618−<div class="sourceCode" id="cb98"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb98-1"></a>(a -> b) -> f a -> f b</code></pre></div>

619−<div class="sourceCode" id="cb99"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb99-1"></a>(a -> (b -> c)) -> f a -> f (b -> c)</code></pre></div>

620−<div class="sourceCode" id="cb100"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb100-1"></a>getMarkup :: Env Markup

621−<a href="#cb100-2"></a>getPrice :: Env Price

622−<a href="#cb100-3"></a>getPayment :: Markup -> Price -> Payment</code></pre></div>

623−<div class="sourceCode" id="cb101"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb101-1"></a>payment :: Env Payment

624−<a href="#cb101-2"></a>payment = fmap getPayment getMarkup <*> getPrice</code></pre></div>

625−<div class="sourceCode" id="cb102"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb102-1"></a>payment = fmap getPayment getMarkup <*> getPrice

626−<a href="#cb102-2"></a>-- ^-------------^

627−<a href="#cb102-3"></a>-- Env Markup -> Env (Price -> Payment)</code></pre></div>

628−<div class="sourceCode" id="cb103"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb103-1"></a>(<$>) = fmap</code></pre></div>

629−<div class="sourceCode" id="cb104"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb104-1"></a>payment = getPayment <$> getMarkup <*> getPrice</code></pre></div>

621+<div class="sourceCode" id="cb99"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb99-1"></a>(a -> b) -> f a -> f b</code></pre></div>

622+<div class="sourceCode" id="cb100"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb100-1"></a>(a -> (b -> c)) -> f a -> f (b -> c)</code></pre></div>

623+<div class="sourceCode" id="cb101"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb101-1"></a>getMarkup :: Env Markup

624+<a href="#cb101-2"></a>getPrice :: Env Price

625+<a href="#cb101-3"></a>getPayment :: Markup -> Price -> Payment</code></pre></div>

626+<div class="sourceCode" id="cb102"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb102-1"></a>payment :: Env Payment

627+<a href="#cb102-2"></a>payment = fmap getPayment getMarkup <*> getPrice</code></pre></div>

628+<div class="sourceCode" id="cb103"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb103-1"></a>payment = fmap getPayment getMarkup <*> getPrice

629+<a href="#cb103-2"></a>-- ^-------------^

630+<a href="#cb103-3"></a>-- Env Markup -> Env (Price -> Payment)</code></pre></div>

631+<div class="sourceCode" id="cb104"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb104-1"></a>(<$>) = fmap</code></pre></div>

632+<div class="sourceCode" id="cb105"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb105-1"></a>payment = getPayment <$> getMarkup <*> getPrice</code></pre></div>

630633</section>

631634<section class="slide level2">

632635

633−<div class="sourceCode" id="cb105"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb105-1"></a>(<*>) :: m (a -> b) -> m a -> m b

634−<a href="#cb105-2"></a>f <*> ma = ma >>= \a -> fmap (\f' -> f' a) f</code></pre></div>

636+<div class="sourceCode" id="cb106"><pre class="sourceCode haskell"><code class="sourceCode haskell"><a href="#cb106-1"></a>(<*>) :: m (a -> b) -> m a -> m b

637+<a href="#cb106-2"></a>mf <*> ma = do

638+<a href="#cb106-3"></a> f <- mf

639+<a href="#cb106-4"></a> a <- ma

640+<a href="#cb106-5"></a> return (f a)</code></pre></div>

641+<div class="sourceCode" id="cb107"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb107-1"></a>ap :: Monad m => m (a -> b) -> m a -> m b

642+<a href="#cb107-2"></a>ap mf ma = do

643+<a href="#cb107-3"></a> f <- mf

644+<a href="#cb107-4"></a> a <- ma

645+<a href="#cb107-5"></a> return (f a)</code></pre></div>

646+<div class="sourceCode" id="cb108"><pre class="sourceCode haskell fragment"><code class="sourceCode haskell"><a href="#cb108-1"></a>instance Monad ... where ...

647+<a href="#cb108-2"></a>

648+<a href="#cb108-3"></a>instance Applicative ... where

649+<a href="#cb108-4"></a> pure = return

650+<a href="#cb108-5"></a> (<*>) = ap</code></pre></div>

635651</section></section>

636652 </div>

637653 </div>

3.md+56−32

@@ -258,7 +258,7 @@ instance Monad (Either e) where

258258instance Monad WithLog where

259259 (<=<) f g x = WithLog x3 (log1 <> log2)

260260 where

261− (WithLog x2 log1) = g x1

261+ (WithLog x2 log1) = g x

262262 (WithLog x3 log2) = f x2

263263```

264264

@@ -312,8 +312,8 @@ buyCoffee order = getCoffee order >>= payForCoffee

312312```

313313

314314```{ .haskell .fragment }

315−maybeBuyCoffee :: Myabe Order -> Maybe Payment

316−maybeBuyCoffee order = order >>= buyCoffee

315+maybeBuyCoffee :: Maybe Order -> Maybe Payment

316+maybeBuyCoffee mOrder = mOrder >>= buyCoffee

317317```

318318

319319```{ .haskell .fragment }

@@ -339,16 +339,16 @@ maybeBuyCoffee order = order >>= buyCoffee

339339

340340```{ .haskell }

341341(>>=) :: Monad m => m b -> (b -> m c) -> m c

342−(>>=) mb f = ( (\() -> mb) >=> f ) ()

342+(>>=) mb bmc = ( (\() -> mb) >=> bmc ) ()

343343```

344344

345345```{ .haskell .fragment }

346−(>>=) mb f = ( (\() -> mb) >=> f ) ()

347−-- () -> m b |

348−-- b -> m c

346+(>>=) mb bmc = ( (\() -> mb) >=> bmc ) ()

347+-- () -> m b |

348+-- b -> m c

349349--

350−-- ^-------------------^

351−-- () -> m c

350+-- ^-----------------------^

351+-- () -> m c

352352```

353353

354354---

@@ -433,31 +433,20 @@ data Reader r a = Reader

433433

434434[`r` -- то, что у нас в "окружении".]{ .fragment }

435435

436−```{ .haskell .fragment }

437−getCoffee :: Order -> Reader Markup Coffee

438−payForCoffee :: Coffee -> Reader Markup Payment

439−```

440−

441−```{ .haskell .fragment }

442−payment :: Payment

443−payment = runReader (payForCoffee coffee) markup

444−```

445−

446436---

447437

448438```{ .haskell }

449439data Reader r a = Reader { runReader :: r -> a }

450440

451−getCoffee :: Order -> Reader Markup Coffee

452−payForCoffee :: Coffee -> Reader Markup Payment

441+getCoffee :: Order -> Markup -> Coffee

442+payForCoffee :: Coffee -> Markup -> Payment

453443```

454444

455445```{ .haskell .fragment }

456−buyCoffee :: Order -> Reader Markup Payment

457−buyCoffee = payForCoffee <=< getCoffee

446+getCoffee :: Order -> Reader Markup Coffee

447+payForCoffee :: Coffee -> Reader Markup Payment

458448```

459449

460−

461450```{ .haskell .fragment }

462451type PricingEnv = Reader Markup

463452```

@@ -465,10 +454,18 @@ type PricingEnv = Reader Markup

465454```{ .haskell .fragment }

466455getCoffee :: Order -> PricingEnv Coffee

467456payForCoffee :: Coffee -> PricingEnv Payment

457+```

458+

459+```{ .haskell .fragment }

468460buyCoffee :: Order -> PricingEnv Payment

469461buyCoffee = payForCoffee <=< getCoffee

470462```

471463

464+```{ .haskell .fragment }

465+payment :: Payment

466+payment = runReader (buyCoffee order) markup

467+```

468+

472469---

473470

474471```{ .haskell }

@@ -533,20 +530,27 @@ bar :: Reader r a

533530qux :: a -> Reader r b

534531

535532foo :: Reader r b

536−foo = bar >>= \a -> qux a

533+foo = bar >>= \x -> qux x

537534```

538535

539536```{ .haskell .fragment }

540537foo = do

541− a <- bar

542− qux a

538+ -- (x :: a) <- (bar :: Reader r a)

539+ x <- bar

540+ qux x

543541```

544542

545543```{ .haskell .fragment }

546544foo = do

547− a <- bar

548− b <- qux a

549− return b

545+ -- (x :: a) <- (bar :: Reader r a)

546+ x <- bar

547+ -- (y :: b) <- (qux x :: Reader r b)

548+ y <- qux x

549+ return y

550+```

551+

552+```{ .haskell .fragment }

553+foo = bar >>= \x -> qux x >>= return

550554```

551555

552556---

@@ -618,6 +622,7 @@ ask = Reader (\r -> r)

618622```{ .haskell .fragment }

619623getCoffeePrice :: Coffee -> PricingEnv Price

620624getCoffeePrice coffee = do

625+ -- (markup :: Markup) <- (ask :: PricingEnv Markup)

621626 markup <- ask

622627 let coffePrice = getCoffeePrice coffee

623628 return (coffee + markup)

@@ -835,7 +840,26 @@ payment = getPayment <$> getMarkup <*> getPrice

835840

836841---

837842

838−```{ .haskell .fragment }

843+```{ .haskell }

839844(<*>) :: m (a -> b) -> m a -> m b

840−f <*> ma = ma >>= \a -> fmap (\f' -> f' a) f

845+mf <*> ma = do

846+ f <- mf

847+ a <- ma

848+ return (f a)

849+```

850+

851+```{ .haskell .fragment }

852+ap :: Monad m => m (a -> b) -> m a -> m b

853+ap mf ma = do

854+ f <- mf

855+ a <- ma

856+ return (f a)

857+```

858+

859+```{ .haskell .fragment }

860+instance Monad ... where ...

861+

862+instance Applicative ... where

863+ pure = return

864+ (<*>) = ap

841865```