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promote

promote(xs...)

Convert all arguments to their common promotion type (if any), and return them all (as a tuple).

Examples

In the Julia programming language, the function promote(xs...) is used to convert all arguments to their common promotion type (if any) and return them all as a tuple.

julia> promote(1.5, 2)
(1.5, 2.0)

In this example, both 1.5 and 2 are promoted to their common type, which is Float64. The function returns a tuple (1.5, 2.0).

julia> promote(3, 4, 5)
(3, 4, 5)

In this case, all arguments are already of the same type (Int64), so no promotion is needed. The function returns a tuple (3, 4, 5).

julia> promote(1, 2.5, 3//2)
(1.0, 2.5, 1.5)

Here, the arguments have different types (Int64, Float64, Rational{Int64}), so they are promoted to their common type, which is Float64. The function returns a tuple (1.0, 2.5, 1.5).

Common mistake example:

julia> promote(1, "two")
ERROR: MethodError: no promotion exists between Int64 and String

In this example, the arguments 1 and "two" have incompatible types (Int64 and String). The promote function requires a common promotion type, and if it doesn't exist, it throws a MethodError. Ensure that the arguments can be promoted to a common type before using the promote function.

See Also

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