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issorted

issorted(v, [by=,] [lt=,] [rev=false])

Test whether a vector is in sorted order. The by, lt and rev keywords modify what order is considered to be sorted just as they do for sort.

Examples

Check if a vector is sorted in ascending order:

julia> v = [1, 2, 3, 4];
julia> issorted(v)
true

This example checks if the vector v is sorted in ascending order. Since it is sorted, the function returns true.

Check if a vector is sorted in descending order:

julia> v = [4, 3, 2, 1];
julia> issorted(v, rev=true)
true

Here, the rev=true argument is used to check if the vector v is sorted in descending order. The function returns true because the vector is indeed sorted in descending order.

Check if a vector of strings is sorted based on string length:

julia> v = ["apple", "banana", "orange", "grape"];
julia> issorted(v, by=length)
true

In this example, the by=length argument is used to check if the vector of strings v is sorted based on string length. Since the strings are sorted in increasing order of length, the function returns true.

Check if a vector is sorted using a custom comparison function:

julia> v = [2.5, 6.7, 4.3, 9.1];
julia> issorted(v, lt=(x, y)->abs(x) < abs(y))
false

Here, the lt=(x, y)->abs(x) < abs(y) argument is used to define a custom comparison function. The function checks if the absolute values of elements in the vector v are sorted in ascending order. Since the vector is not sorted in this manner, the function returns false.

Common mistake example:

julia> v = [3, 1, 2];
julia> issorted(v, by=length)
ERROR: MethodError: no method matching length(::Int64)

In this example, the by=length argument is used with the issorted function, expecting to sort a vector of integers based on their length. However, the length function is not applicable to integers, resulting in a MethodError. It's important to provide appropriate arguments based on the type of elements in the vector.

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