| title | description | canonical |
|---|---|---|
Tuple | Tuple types and values in ReScript | /docs/manual/v11.0.0/tuple |
Tuples are a ReScript-specific data structure that don't exist in JavaScript. They are:
- immutable
- ordered
- fix-sized at creation time
- heterogeneous (can contain different types of values)
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letageAndName= (24, "Lil' ReScript") letmy3dCoordinates= (20.0, 30.5, 100.0)varageAndName=[24,"Lil' ReScript"];varmy3dCoordinates=[20.0,30.5,100.0];Tuples' types can be used in type annotations as well. Tuple types visually resemble tuples values.
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letageAndName: (int, string) = (24, "Lil' ReScript") // a tuple type aliastypecoord3d= (float, float, float) letmy3dCoordinates: coord3d= (20.0, 30.5, 100.0)varageAndName=[24,"Lil' ReScript"];varmy3dCoordinates=[20.0,30.5,100.0];Note: there's no tuple of size 1. You'd just use the value itself.
To get a specific member of a tuple, destructure it:
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let (_, y, _) =my3dCoordinates// now you've retrieved yvary=30.5;The _ means you're ignoring the indicated members of the tuple.
Tuples aren't meant to be updated mutatively. You'd create new ones by destructuring the old ones:
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letcoordinates1= (10, 20, 30) let (c1x, _, _) =coordinates1letcoordinates2= (c1x+50, 20, 30)varcoordinates1=[10,20,30];varc1x=10;varcoordinates2=[60,20,30];You'd use tuples in handy situations that pass around multiple values without too much ceremony. For example, to return many values:
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letgetCenterCoordinates= () => { letx=doSomeOperationsHere() lety=doSomeMoreOperationsHere() (x, y) }functiongetCenterCoordinates(param){varx=doSomeOperationsHere(undefined);vary=doSomeMoreOperationsHere(undefined);return[x,y];}Try to keep the usage of tuple local. For data structures that are long-living and passed around often, prefer a record, which has named fields.
