Difference between revisions of "Higher Order Functions Hall of Fame Assignment"

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=Code To Implement=
 
=Code To Implement=
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==Map==
+
==Higher-order Functions==
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{{JavaToImplement|MapHof|map|hof.map.assignment}}
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{{JavaToImplement|Hof|filter<br/>foldLeft<br/>foldRight<br/>map<br/>find<br/>|hof.util.exercise}}
  
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<nowiki>public static <T, R> ImmutableList<R> map(Function<T, R> f, ImmutableList<T> list)</nowiki> {{HofHof}}
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===filter {{HofHof}}===
 +
[https://smlfamily.github.io/Basis/list.html#SIG:LIST.filter:VAL SML List filter]
  
−
{{JavaToImplement|MapHofApps|mapToLengths<br>mapToStrictlyLessThan|hof.map.assignment}}
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<syntaxhighlight lang="java>
 +
public static <E> ImList<E> filter(Predicate<E> predicate, ImList<E> list)
 +
</syntaxhighlight>
  
−
<nowiki>public static ImmutableList<Integer> mapToLengths(ImmutableList<String> texts)</nowiki>
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===foldLeft {{HofHof}}===
 +
[https://smlfamily.github.io/Basis/list.html#SIG:LIST.foldl:VAL SML List foldl]
  
−
<nowiki>public static ImmutableList<Boolean> mapToStrictlyLessThan(ImmutableList<Integer> xs, int threshold)</nowiki>
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:<code>foldLeft(f, initial_value, [x1, x2, ..., xn])</code>
 +
:returns <code>f(xn,...,f(x2, f(x1, initial_value))...)</code> or <code>initial_value</code> if the list is empty.
  
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==Filter==
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<syntaxhighlight lang="java>
−
{{JavaToImplement|FilterHof|filter|hof.filter.assignment}}
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public static <E, R> R foldLeft(BiFunction<E, R, R> f, R acc, ImList<E> list)
 +
</syntaxhighlight>
 +
===foldRight {{HofHof}}===
 +
[https://smlfamily.github.io/Basis/list.html#SIG:LIST.foldr:VAL SML List foldr]
  
−
<nowiki>public static <E> ImmutableList<E> filter(Predicate<E> predicate, ImmutableList<E> list)</nowiki> {{HofHof}}
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:<code>foldRight(f, initial_value, [x1, x2, ..., xn])</code>
 +
:returns <code>f(x1, f(x2, ..., f(xn, init)...))</code> or <code>initial_value</code> if the list is empty.
  
−
{{JavaToImplement|FilterHofApps|filterWordsWhichContainAllVowels<br>filterEvens|hof.map.assignment}}
+
<syntaxhighlight lang="java>
 +
public static <E, R> R foldRight(BiFunction<E, R, R> f, R acc, ImList<E> list)
 +
</syntaxhighlight>
 +
===map {{HofHof}}===
 +
[https://smlfamily.github.io/Basis/list.html#SIG:LIST.map:VAL SML List map]
  
−
<nowiki>public static ImmutableList<String> filterWordsWhichContainAllVowels(ImmutableList<String> words)</nowiki>
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<syntaxhighlight lang="java>
 +
public static <E, R> ImList<R> map(Function<E, R> f, ImList<E> list)
 +
</syntaxhighlight>
 +
===find {{HofHof}}===
 +
[https://smlfamily.github.io/Basis/list.html#SIG:LIST.find:VAL SML List map]
  
−
<nowiki>public static ImmutableList<Integer> filterEvens(ImmutableList<Integer> xs)</nowiki>
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<syntaxhighlight lang="java>
 +
public static <E> Optional<E> find(Predicate<E> predicate, ImList<E> list)
 +
</syntaxhighlight>
  
−
Lexical scope is not unique to ML. Nearly all programming languages use lexical scope, including Java.
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==Clients==
 +
{{JavaToImplement|HofClients|toOnlyWordsWhichContainAllVowels<br>firstPalindrome<br/>sum<br>countBetweenMinAndMaxExclusive<br/>reverse<br>toLengths<br/>toStrictlyLessThan|hof.clients.exercise}}
  
−
First, we will build the utility methods: foldLeft (which can be easily built with tail recursion) and foldRight (which cannot).
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===toOnlyWordsWhichContainAllVowels===
 +
<syntaxhighlight lang="java>
 +
public static ImList<String> toOnlyWordsWhichContainAllVowels(ImList<String> words)
 +
</syntaxhighlight>
  
−
Next, we will build some applications which use fold: sum (which does not require lexical scope) and countBetweenMinAndMaxExclusive (which does).
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===toOnlyEvens===
 +
<syntaxhighlight lang="java>
 +
public static ImList<Integer> toOnlyEvens(ImList<Integer> xs)
 +
</syntaxhighlight>
  
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==Fold==
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===toOnlyWordsWhichContainAllVowels===
−
{{JavaToImplement|FoldHof|foldLeft<br>foldRight|hof.fold.assignment}}
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<syntaxhighlight lang="java>
 +
public static ImList<String> toOnlyWordsWhichContainAllVowels(ImList<String> words)
 +
</syntaxhighlight>
  
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[http://sml-family.org/Basis/list.html SML List Reference]
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===firstPalindrome===
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===foldLeft===
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<syntaxhighlight lang="java>
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<nowiki>public static <A, B> A foldLeft(BiFunction<A, B, A> f, A acc, ImmutableList<B> list)</nowiki> {{HofHof}}
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public static Optional<String> firstPalindrome(ImList<String> words)
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:<code>foldLeft(f, initial_value, [x1, x2, ..., xn])</code>
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</syntaxhighlight>
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:returns <code>f(xn,...,f(x2, f(x1, initial_value))...)</code> or <code>initial_value</code> if the list is empty.
 
  
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===foldRight===
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===sum===
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<nowiki>public static <A, B> A foldRight(BiFunction<A, B, A> f, A acc, ImmutableList<B> list)</nowiki> {{HofHof}}
+
<syntaxhighlight lang="java>
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:<code>foldRight(f, initial_value, [x1, x2, ..., xn])</code>
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public static int sum(ImList<Integer> xs)
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:returns <code>f(x1, f(x2, ..., f(xn, init)...))</code> or <code>initial_value</code> if the list is empty.
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</syntaxhighlight>
  
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==Fold Apps==
 
−
{{JavaToImplement|FoldHofApps|sum<br>countBetweenMinAndMaxExclusive|hof.map.assignment}}
 
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===sum===
 
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<nowiki>public static int sum(ImmutableList<Integer> xs)</nowiki>
 
 
===countBetweenMinAndMaxExclusive===
 
===countBetweenMinAndMaxExclusive===
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<nowiki>public static int countBetweenMinAndMaxExclusive(int min, int maxExclusive, ImmutableList<Integer> xs)</nowiki>
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<syntaxhighlight lang="java>
 +
public static int countBetweenMinAndMaxExclusive(int min, int maxExclusive, ImList<Integer> xs)
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</syntaxhighlight>
 +
 
 +
===reverse===
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<syntaxhighlight lang="java>
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public static <E> ImList<E> reverse(ImList<E> xs)
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</syntaxhighlight>
 +
 
 +
===toLengths===
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<syntaxhighlight lang="java>
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public static ImList<Integer> toLengths(ImList<String> texts)
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</syntaxhighlight>
 +
 
 +
===toStrictlyLessThan===
 +
<syntaxhighlight lang="java>
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public static ImList<Boolean> toStrictlyLessThan(ImList<Integer> xs, int threshold)
 +
</syntaxhighlight>
  
 
=Test=
 
=Test=
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{{TestSuite|HigherOrderFunctionTestSuite|hof.assignment}}
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{{TestSuite|HigherOrderFunctionTestSuite|hof}}
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==Map==
 
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{{TestSuite|MapTestSuite|hof.map.assignment}}
 
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==Filter==
 
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{{TestSuite|FilterTestSuite|hof.map.assignment}}
 
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=Test=
 
−
{{TestSuite|FoldTestSuite|hof.fold.assignment}}
 

Latest revision as of 03:32, 12 October 2023

Code To Implement

Higher-order Functions

class: Hof.java Java.png
methods: filter
foldLeft
foldRight
map
find
package: hof.util.exercise
source folder: src/main/java

filter Laurel Wreath

SML List filter 

public static <E> ImList<E> filter(Predicate<E> predicate, ImList<E> list)

foldLeft Laurel Wreath

SML List foldl

foldLeft(f, initial_value, [x1, x2, ..., xn])
returns f(xn,...,f(x2, f(x1, initial_value))...) or initial_value if the list is empty.
public static <E, R> R foldLeft(BiFunction<E, R, R> f, R acc, ImList<E> list)

foldRight Laurel Wreath

SML List foldr

foldRight(f, initial_value, [x1, x2, ..., xn])
returns f(x1, f(x2, ..., f(xn, init)...)) or initial_value if the list is empty.
public static <E, R> R foldRight(BiFunction<E, R, R> f, R acc, ImList<E> list)

map Laurel Wreath

SML List map 

public static <E, R> ImList<R> map(Function<E, R> f, ImList<E> list)

find Laurel Wreath

SML List map 

public static <E> Optional<E> find(Predicate<E> predicate, ImList<E> list)

Clients

class: HofClients.java Java.png
methods: toOnlyWordsWhichContainAllVowels
firstPalindrome
sum
countBetweenMinAndMaxExclusive
reverse
toLengths
toStrictlyLessThan
package: hof.clients.exercise
source folder: src/main/java

toOnlyWordsWhichContainAllVowels

public static ImList<String> toOnlyWordsWhichContainAllVowels(ImList<String> words)

toOnlyEvens

public static ImList<Integer> toOnlyEvens(ImList<Integer> xs)

toOnlyWordsWhichContainAllVowels

public static ImList<String> toOnlyWordsWhichContainAllVowels(ImList<String> words)

firstPalindrome

public static Optional<String> firstPalindrome(ImList<String> words)

sum

public static int sum(ImList<Integer> xs)

countBetweenMinAndMaxExclusive

public static int countBetweenMinAndMaxExclusive(int min, int maxExclusive, ImList<Integer> xs)

reverse

public static <E> ImList<E> reverse(ImList<E> xs)

toLengths

public static ImList<Integer> toLengths(ImList<String> texts)

toStrictlyLessThan

public static ImList<Boolean> toStrictlyLessThan(ImList<Integer> xs, int threshold)

Test

class: HigherOrderFunctionTestSuite.java Junit.png
package: hof
source folder: src/test/java
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