I recently learned of the existence of the => operator, which forms an element of type Pair: julia> 2 => ones(4) 2 => [1.0, 1.0, 1.0, 1.0] which makes a Pair. I just assumed Pair was a convenience type synonym for a length 2 Tuple, but it’s not. julia> typeof((1,2)) == typeof(1 => 2) false Just …

A 2-tuple is a collection of elements that may have nothing to do with each other; a pair associates the first element with the second. It’s typically used to relate dictionary keys with their respective values, for instance. Regarding functionality differences, as their docstring tell, a Pair is t…

The reason we need a difference is to facilitate broadcast. Broacasting over (1,2) applies to the two elements separately, but broadcasting treats 1=>2 as a scalar.

[image] malacroi: The reason we need a difference is to facilitate broadcast. No, the Pair type came long before the dot syntax for broadcasting.

[image] purplishrock: Just curious as to what functionality Pair provides that a two element tuple could not ? That’s not the right question in Julia. All 2-element collections could do the same thing. But, of course, you may not want them to do the same thing, and having a different type al…

[image] Tamas_Papp: All 2-element collections could do the same thing. cough arrays cough

Of course pairs and 2-tuples are structurally the same, and 2-tuples can just as well represent an association from the first item to the second item (that is the definition of a mathematical functional relation after all: [1] , [2] , [3] , [4] , [5] , [6] ). The reason for the distinction is to clarify …

Why is there a type "Pair"?

New to Julia

sijo December 12, 2020, 9:39am 5

See here for a previous (short) discussion: https://discourse.julialang.org/t/pair-a-b-vs-tuple-a-b/

Topic		Replies	Views
`Pair{A,B}` vs. `Tuple{A,B}` General Usage	4	6237	May 20, 2021
`(x, y)` works but `x => y` doesn't General Usage	17	1951	June 11, 2021
Broadcasting and pairs using `.=>` General Usage	3	691	May 29, 2019
Incomplete description of type vector of pairs General Usage question , inference , type-of-pair	6	923	June 15, 2022
Union all Types General Usage type , functions , type-hierarchy	2	328	November 11, 2022

Why is there a type "Pair"?

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