# issubset

``````..  issubset(A, S) -> Bool
âŠ†(A,S) -> Bool

Return ``true`` if ``A`` is a subset of or equal to ``S``.``````

## Examples

Check if every element of `a` is in `b`:

``````julia> issubset([1, 2, 3], [1, 2, 3, 4, 5])
true``````

This example checks if every element in `[1, 2, 3]` is present in `[1, 2, 3, 4, 5]`. Since all elements are present, it returns `true`.

``````julia> issubset([4, 5, 6], [1, 2, 3])
false``````

In this case, not all elements in `[4, 5, 6]` are present in `[1, 2, 3]`, so it returns `false`.

Check if `a` is a proper subset of `b`:

``````julia> issubset([1, 2], [1, 2, 3])
true``````

Here, `[1, 2]` is a proper subset of `[1, 2, 3]`, so it returns `true`.

``````julia> issubset([1, 2, 3], [1, 2, 3])
false``````

Since `[1, 2, 3]` is not a proper subset of itself, it returns `false`.

Check if `a` is not a subset of `b`:

``````julia> issubset([4, 5, 6], [1, 2, 3])
true``````

In this example, `[4, 5, 6]` is not a subset of `[1, 2, 3]`, so it returns `true`.

``````julia> issubset([1, 2, 3], [1, 2, 3])
false``````

Since `[1, 2, 3]` is a subset of itself, it returns `false`.

Common mistake example:

``````julia> issubset([1, 2, 3], 4)
ERROR: MethodError: no method matching issubset(::Array{Int64,1}, ::Int64)``````

In this example, the second argument provided is not an iterable collection. The `issubset` function expects both arguments to be collections that can be iterated over. Make sure to provide valid collections as arguments to `issubset`.