Difference between revisions of "Fold Assignment"
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{{JavaToImplement|FoldHof|foldLeft<br>foldRight|hof.fold.assignment}} | {{JavaToImplement|FoldHof|foldLeft<br>foldRight|hof.fold.assignment}} | ||
| − | [ | + | [https://smlfamily.github.io/Basis/list.html SML List Reference] |
===foldLeft=== | ===foldLeft=== | ||
| − | <nowiki>public static <A, B> A foldLeft(BiFunction<A, B, A> f, A acc, ImmutableList<B> list)</nowiki> {{HofHof}} | + | <nowiki>public static <A, B> A foldLeft(BiFunction<A, B, A> f, A acc, ImmutableList<B> list)</nowiki> {{HofHof}} |
:<code>foldLeft(f, initial_value, [x1, x2, ..., xn])</code> | :<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. | :returns <code>f(xn,...,f(x2, f(x1, initial_value))...)</code> or <code>initial_value</code> if the list is empty. | ||
===foldRight=== | ===foldRight=== | ||
| − | <nowiki>public static <A, B> A foldRight(BiFunction<A, B, A> f, A acc, ImmutableList<B> list)</nowiki> {{HofHof}} | + | <nowiki>public static <A, B> A foldRight(BiFunction<A, B, A> f, A acc, ImmutableList<B> list)</nowiki> {{HofHof}} |
:<code>foldRight(f, initial_value, [x1, x2, ..., xn])</code> | :<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. | :returns <code>f(x1, f(x2, ..., f(xn, init)...))</code> or <code>initial_value</code> if the list is empty. | ||
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{{JavaToImplement|FoldHofApps|sum<br>countBetweenMinAndMaxExclusive|hof.map.assignment}} | {{JavaToImplement|FoldHofApps|sum<br>countBetweenMinAndMaxExclusive|hof.map.assignment}} | ||
===sum=== | ===sum=== | ||
| − | <nowiki>public static int sum(ImmutableList<Integer> xs)</nowiki> | + | <nowiki>public static int sum(ImmutableList<Integer> xs)</nowiki> |
===countBetweenMinAndMaxExclusive=== | ===countBetweenMinAndMaxExclusive=== | ||
| − | <nowiki>public static int countBetweenMinAndMaxExclusive(int min, int maxExclusive, ImmutableList<Integer> xs)</nowiki> | + | <nowiki>public static int countBetweenMinAndMaxExclusive(int min, int maxExclusive, ImmutableList<Integer> xs)</nowiki> |
=Test= | =Test= | ||
{{TestSuite|FoldTestSuite|hof.fold.assignment}} | {{TestSuite|FoldTestSuite|hof.fold.assignment}} | ||
Latest revision as of 04:41, 28 January 2022
Lexical scope is not unique to ML. Nearly all programming languages use lexical scope, including Java.
First, we will build the utility methods: foldLeft (which can be easily built with tail recursion) and foldRight (which cannot).
Next, we will build some applications which use fold: sum (which does not require lexical scope) and countBetweenMinAndMaxExclusive (which does).
Contents
Code To Implement
Fold
| class: | FoldHof.java |  |
| methods: | foldLeft foldRight |
|
| package: | hof.fold.assignment | |
| source folder: | src/main/java |
foldLeft
public static <A, B> A foldLeft(BiFunction<A, B, A> f, A acc, ImmutableList<B> list) 
foldLeft(f, initial_value, [x1, x2, ..., xn])- returns
f(xn,...,f(x2, f(x1, initial_value))...)orinitial_valueif the list is empty.
foldRight
public static <A, B> A foldRight(BiFunction<A, B, A> f, A acc, ImmutableList<B> list)
foldRight(f, initial_value, [x1, x2, ..., xn])- returns
f(x1, f(x2, ..., f(xn, init)...))orinitial_valueif the list is empty.
Fold Apps
| class: | FoldHofApps.java | |
| methods: | sum countBetweenMinAndMaxExclusive |
|
| package: | hof.map.assignment | |
| source folder: | src/main/java |
sum
public static int sum(ImmutableList<Integer> xs)
countBetweenMinAndMaxExclusive
public static int countBetweenMinAndMaxExclusive(int min, int maxExclusive, ImmutableList<Integer> xs)
Test
| class: | FoldTestSuite.java |  |
| package: | hof.fold.assignment | |
| source folder: | src/test/java |
