what does it mean `[nil, true, 99].all? ` in ruby

In Ruby, the [nil, true, 99].all? expression checks if all elements of the array [nil, true, 99] satisfy a certain condition.

The all? method is an Enumerable method in Ruby that returns true if the given block returns true for every element in the collection.

In this case, since no block is provided as an argument to all?, the expression will return true if all elements in the array are truthy (i.e., not nil or false).

Let's see some examples:

main.rb
# Example 1
[true, true, true].all?   # Output: true
# Since all elements are truthy, the result is true

# Example 2
[nil, true, 99].all?     # Output: false
# The first element is nil, which is not truthy. So, the result is false

# Example 3
[1, 2, 3, 4].all? { |num| num > 0 }   # Output: true
# The block checks if each element is greater than 0. Since all elements satisfy the condition, the result is true
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Note: It's important to understand that [nil, true, 99].all? returns false if there is at least one element that is falsy (i.e., nil or false). If you need to check for the presence of a specific value, you may want to use other methods like include?.