copy

copy(x)

Create a shallow copy of x: the outer structure is copied, but not all internal values. For example, copying an array produces a new array with identically-same elements as the original.

Examples

Create a copy of an array:

julia> arr = [1, 2, 3, 4, 5];
julia> arr_copy = copy(arr);
julia> arr_copy[1] = 10;
julia> arr
5-element Array{Int64,1}:
1
2
3
4
5
julia> arr_copy
5-element Array{Int64,1}:
10
2
3
4
5

This example demonstrates that modifying the copied array (arr_copy) does not affect the original array (arr).

Copy a dictionary:

julia> dict = Dict("a" => 1, "b" => 2, "c" => 3);
julia> dict_copy = copy(dict);
julia> dict_copy["b"] = 20;
julia> dict
Dict{String,Int64} with 3 entries:
"a" => 1
"b" => 2
"c" => 3
julia> dict_copy
Dict{String,Int64} with 3 entries:
"a" => 1
"b" => 20
"c" => 3

Here, the copied dictionary (dict_copy) can be modified independently without affecting the original dictionary (dict).

Copy a string:

julia> str = "Hello, Julia!";
julia> str_copy = copy(str);
julia> str_copy[1] = 'J';
julia> str
"Hello, Julia!"
julia> str_copy
"Jello, Julia!"

In this example, copying a string allows you to modify the copied string without modifying the original string.

Common mistake example:

julia> a = [1, 2, 3];
julia> b = a;
julia> c = copy(a);
julia> b[1] = 10;
julia> c[1] = 20;
julia> a
3-element Array{Int64,1}:
 10
 2
 3
julia> b
3-element Array{Int64,1}:
 10
 2
 3
julia> c
3-element Array{Int64,1}:
 20
 2
 3

In this example, assigning b = a creates a reference to the original array, so modifying b also modifies a. However, using copy(a) creates a new array c that is independent of a.

User Contributed Notes

Add a Note

The format of note supported is markdown, use triple backtick to start and end a code block.

copy

Examples

See Also

User Contributed Notes

Add a Note