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Questions - hashmap

Scala: Set of tuples doesn't allow me to add a "straight" tuple

I have this code of a mutable Hashmap with a mutable Set with tuples: val field = mutable.HashMap[String, mutable.Set[(Pos3, Pos3)]]() In foreach loop I'm populating the field scanner.combinations(...
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dr jerry

scala

hashmap

set

tuples

Votes: 0

Answers: 1

Latest Answer

Remember that when you do foo += x that is just sugar syntax for foo.+=(x) (i.e. omit the dot and the parenthesis) But when you do foo += (x, y) the compiler thinks you are just omitting the dot inste...
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Luis Miguel Mejía Suárez

Creating a HashMap in Rust using the fold iterator method

I am trying to create a word count HashMap from an array of words using Entry and iterators in Rust. When I try as below, use std::collections::HashMap; fn main () { let corpus = ["foo",...
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Py_Dream

rust

hashmap

iterator

Votes: 0

Answers: 1

Latest Answer

Like explained in the comment from @PitaJ, *acc.entry(word).or_insert(0) += 1 has the type () while the compiler expects fold()'s callback to return the next state each time (it is sometimes called re...
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Chayim Friedman

Transform array of objects to a map indexed by object key

I'm trying to convert an array of object to a map, indexed by an attribue value of the Object in typescript 4.1.5 Furthermore I want only the attributes of a certain type (here string) A very similar ...
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Nainpo

arrays

typescript

hashmap

Votes: 0

Answers: 1

Latest Answer

To filter the keys based on which have a string value you can't use Extarct that filters the keys which are strings (not number or symbol). You can use KeyOfType described here type KeyOfType<T, V&...
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Titian Cernicova-Dragomir

How to check if Object is instanceof HashMap&lt;?,?&gt;[] in Java?

I have in java an array of HashMaps HashMap<String, String>[] convertTags = new HashMap[1]; HashMap<String, String> tag = new HashMap<>(); tag.put("key", "test-tag&quo...
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Jayleen

java

hashmap

Votes: 0

Answers: 1

Latest Answer

When doing type checks with instanceof, you cannot use a generic type as the check: you must use a raw type. The reason for this is simple: most of the generic type information is erased at compile-...
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scottb

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