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Comment by 3PS | Hacker News Reader

> "hash" in this context means what other languages would call a hash map

Interesting. The only other time I've seen this term used for a hash map is in the context of Redis hashes [0], which confused me to no end when I first encountered them for the same reason. Given that Redis itself is written in C, I wonder where the term originated.

[0] https://redis.io/docs/data-types/hashes/

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This got me curious, so I went and looked what it was called in a few languages.

  Perl: Hash
  Ruby: Hash
  PHP: HashMap
  Java: HashMap
  Haxe: Map
  Golang: map
  Swift: Dict
  Python: Dict
  C#: Dictionary
  Javascript: Object
  Redis: Hash
  Postgresql: hstore, json

C++: unordered_map

Does PHP have a HashMap class now? I haven’t written PHP for a few years now but associative array used to be how they were referred to.

Yeah, I pretty sure Perl also called them associative arrays, but like you I haven’t written much Perl since Perl 4/5.

In all my time as a Perl dev (since 1996) I don't think I've ever heard the term "associative array" except at the start of `perldoc perldata` - which says they're known as hashes and then never uses the term again.

    DESCRIPTION
      Variable names
        Perl has three built-in data types: scalars, arrays of scalars, and
        associative arrays of scalars, known as "hashes". A scalar is a single
        string (of any size, limited only by the available memory), number, or a
        reference to something (which will be discussed in perlref). Normal
        arrays are ordered lists of scalars indexed by number, starting with 0.
        Hashes are unordered collections of scalar values indexed by their
        associated string key.

Hash is ubiquitous.

Yes they used to be called Associative Arrays. I think the change occurred between Perl4 & Perl5.

In Programming Perl it says "Associative Arrays" in 1st edition and "Hashes (Associative Arrays)" in 2nd edition.

NB. 2nd edition was the first to cover Perl5

It doesn't, at least according to the current documentation.

Not sure why they would need a class for that when they already have a primitive type that does the job. I guess maybe a new OO interface will have its parameters ordered more consistently?

JavaScript also has Map. Which is more general since the keys don't have to be strings.

Keys do not need to be strings in Java either, you need to properly implement equals and hashCode() methods though for the key type.

Also Java has like ten different implementations of Map<K,V> depending on various use cases.

I wasn't comparing to Java. I was commenting on

> Javascript: Object

And in javascript, if you use an Object as a map, the keys do have to be strings (if they aren't already, they are converted into strings).

Associative array in PHP. As opposed to indexed array.

The oldest example I can think of is Perl.

Perl, probably.

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