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fill!

fill!(A, x)

Fill array A with the value x. If x is an object reference, all elements will refer to the same object. fill!(A, Foo()) will return A filled with the result of evaluating Foo() once.

Examples

julia> foo = Array(Int8,1,2);
julia> fill!(foo, 42)
1x2 Array{Int8,2}:
 42     42

Referencing another collection

 julia> foo = [1,2];
 julia> bar = Array(Any,1);
 julia> fill!(bar,foo)
 1-element Array{Any,1}:
  [1,2]
 julia> foo[1] = 42;
 julia> bar
 1-element Array{Any,1}:
 [42,2]

Using functions

julia> function Foo()
                    4^3
            end;
julia> bar = Array(Int8,2);
julia> fill!(bar, Foo())
2-element Array{Int64,1}:
 64
 64

1. Fill an array with a specific value:

   julia> arr = [0, 0, 0, 0, 0];
   julia> fill!(arr, 5)
   5-element Array{Int64,1}:
   5
   5
   5
   5
   5

   This example fills the array arr with the value 5.

2. Fill a matrix with a specific value:

   julia> matrix = zeros(3, 3);
   julia> fill!(matrix, 1.5)
   3×3 Array{Float64,2}:
   1.5  1.5  1.5
   1.5  1.5  1.5
   1.5  1.5  1.5

   It fills a matrix of zeros with the value 1.5.

3. Fill an array with a complex number:

   julia> complex_arr = Vector{ComplexF64}(undef, 4);
   julia> fill!(complex_arr, 1 + 2im)
   4-element Array{ComplexF64,1}:
   1.0 + 2.0im
   1.0 + 2.0im
   1.0 + 2.0im
   1.0 + 2.0im

   In this example, it fills an array with complex numbers.

4. Fill an array with a custom object:

   julia> struct Person
             name::String
             age::Int
         end
   julia> people = Vector{Person}(undef, 3);
   julia> fill!(people, Person("John", 25))
   3-element Array{Person,1}:
   Person("John", 25)
   Person("John", 25)
   Person("John", 25)

   The fill! function can also be used to fill an array with custom objects. In this case, it fills an array with instances of the Person struct.

Common mistake example:

julia> arr = [1, 2, 3, 4, 5];
julia> fill!(arr, 1:3)
ERROR: DimensionMismatch("tried to assign 3 elements to 5 destinations")

In this example, an error occurs because the size of the value being filled (1:3) does not match the size of the array (arr). Make sure the dimensions match to avoid such errors when using fill!.

See Also

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