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Deprecated: Return type of WP_Theme::offsetSet($offset, $value) should either be compatible with ArrayAccess::offsetSet(mixed $offset, mixed $value): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/class-wp-theme.php on line 535

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Deprecated: Return type of WP_REST_Request::offsetExists($offset) should either be compatible with ArrayAccess::offsetExists(mixed $offset): bool, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/rest-api/class-wp-rest-request.php on line 960

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Deprecated: Return type of WP_REST_Request::offsetSet($offset, $value) should either be compatible with ArrayAccess::offsetSet(mixed $offset, mixed $value): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/rest-api/class-wp-rest-request.php on line 992

Deprecated: Return type of WP_REST_Request::offsetUnset($offset) should either be compatible with ArrayAccess::offsetUnset(mixed $offset): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/rest-api/class-wp-rest-request.php on line 1003

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Deprecated: Return type of WP_Block_List::next() should either be compatible with Iterator::next(): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/class-wp-block-list.php on line 175

Deprecated: Return type of WP_Block_List::key() should either be compatible with Iterator::key(): mixed, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/class-wp-block-list.php on line 164

Deprecated: Return type of WP_Block_List::valid() should either be compatible with Iterator::valid(): bool, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/class-wp-block-list.php on line 186

Deprecated: Return type of WP_Block_List::rewind() should either be compatible with Iterator::rewind(): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/class-wp-block-list.php on line 138

Deprecated: Return type of WP_Block_List::offsetExists($index) should either be compatible with ArrayAccess::offsetExists(mixed $offset): bool, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/class-wp-block-list.php on line 75

Deprecated: Return type of WP_Block_List::offsetGet($index) should either be compatible with ArrayAccess::offsetGet(mixed $offset): mixed, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/class-wp-block-list.php on line 89

Deprecated: Return type of WP_Block_List::offsetSet($index, $value) should either be compatible with ArrayAccess::offsetSet(mixed $offset, mixed $value): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/class-wp-block-list.php on line 110

Deprecated: Return type of WP_Block_List::offsetUnset($index) should either be compatible with ArrayAccess::offsetUnset(mixed $offset): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/class-wp-block-list.php on line 127

Deprecated: Return type of WP_Block_List::count() should either be compatible with Countable::count(): int, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /var/www/twodee/blog/wp-includes/class-wp-block-list.php on line 199

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Deprecated: Creation of dynamic property WPCOM_REST_API_V2_Endpoint_Gutenberg_Available_Extensions::$wpcom_is_site_specific_endpoint is deprecated in /var/www/twodee/blog/wp-content/plugins/jetpack/_inc/lib/core-api/wpcom-endpoints/gutenberg-available-extensions.php on line 20

Deprecated: Creation of dynamic property WPCOM_REST_API_V2_Endpoint_Memberships::$wpcom_is_wpcom_only_endpoint is deprecated in /var/www/twodee/blog/wp-content/plugins/jetpack/_inc/lib/core-api/wpcom-endpoints/memberships.php on line 23

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Deprecated: Creation of dynamic property WPCOM_REST_API_V2_Endpoint_Subscribers::$wpcom_is_wpcom_only_endpoint is deprecated in /var/www/twodee/blog/wp-content/plugins/jetpack/_inc/lib/core-api/wpcom-endpoints/subscribers.php on line 15

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Deprecated: Creation of dynamic property Automattic\Jetpack\Sync\Queue::$random_int is deprecated in /var/www/twodee/blog/wp-content/plugins/jetpack/vendor/automattic/jetpack-sync/src/class-queue.php on line 38

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Deprecated: Creation of dynamic property WP_Block_Type::$plan_check is deprecated in /var/www/twodee/blog/wp-includes/class-wp-block-type.php on line 333

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Deprecated: Creation of dynamic property WP_Term::$object_id is deprecated in /var/www/twodee/blog/wp-includes/class-wp-term.php on line 198
» CS 330 Lecture 26 – More Folding, Composing, Custom Data Types

teaching machines

CS 330 Lecture 26 – More Folding, Composing, Custom Data Types

April 8, 2013 by . Filed under
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cs330, lectures, spring 2013.

Agenda

TODO

Code

today.hs

find' [] needle = Nothing
find' (first:rest) needle
  | (fst first) == needle = Just (snd first)
  | otherwise = find' rest needle

foldr' mix accum [] = accum
foldr' mix accum (first:rest) = mix first (foldr' mix accum rest)

and' = foldr' (&&) True
or' = foldr' (||) False
sum' = foldr' (+) 0
product' = foldr' (*) 1
join' = foldr' (++) []
join'' = foldr' (++) ""
length' = foldr' (\item accum -> 1 + accum) 0
average' l = sum' l / length' l
map' xform = foldr' (\item accum -> xform item:accum) []
filter' predicate = foldr' (\item accum -> if predicate item then item:accum else accum) []

-- countOvers threshold los = length' (filter' (\s -> length' s > threshold) los) 
countOvers threshold = length' . filter' (\s -> length' s > threshold)


data Expr = Add Expr Expr
          | Subtract Expr Expr
          | Negate Expr
          | Literal Double
          | Variable String
          deriving (Show)

evaluate (Add e1 e2) = evaluate e1 + evaluate e2
evaluate (Subtract e1 e2) = evaluate e1 - evaluate e2
evaluate (Negate e) = -1 * evaluate e
evaluate (Literal d) = d
evaluate (Variable name) = error "I'm not there yet. :("
 
data LineSegment = LineSegment Double Double Double Double deriving (Show, Eq)

data Vowel = A | E | I | O | U deriving (Bounded, Show)

seglen (LineSegment x1 y1 x2 y2) = sqrt ((x2 - x1) ^ 2 + (y2 - y1) ^ 2)

instance Ord LineSegment where 
  compare s1 s2 = compare (seglen s1) (seglen s2)

Haiku

Numbers fell on me
Not numbers… Meters… Seconds…
Types grounded physics