In this HackerRank Blocks problem solution in ruby programming, Higher-order functions are one of the key components of functional programming. A higher-order function is a tool that takes other functions as parameters or returns them as a result.
Blocks are nameless methods that can be passed to another method as a parameter.
Passing a block to a method is a great way of data abstraction.
Blocks can either be defined with a keyword do … end or curly braces { … }.
Example:
a). Passing a block to a method that takes no parameter
CODE
def call_block
puts “Start of method.”
yield
puts “End of method.”
end
call_block do
puts “I am inside call_block method.”
end
OUTPUT
Start of method.
I am inside call_block method.
End of method.
In this example, a block is passed to the call_block method.
To invoke this block inside the method, we used a keyword, yield.
Calling yield will execute the code within the block that is provided to the method.
b). Passing a block to a method that takes one or more parameters.
CODE
def calculate(a,b)
yield(a, b)
end
puts calculate(15, 10) {|a, b| a – b}
OUTPUT
5
In this example, we have defined a method calculate that takes two parameters a and b.
The yield statement invokes the block with parameters a and b, and executes it.
Task
You are given a partially complete code. Your task is to fill in the blanks (_______).
The factorial method computes: n! { n x n – 1 x … 2 x 1 }.
Problem solution.
def factorial
yield
end
n = gets.to_i
factorial do
puts "#{(1..n).inject(:*) || 1}"
end
Second solution.
def factorial(n)
x = (1..n).inject(:*) || 1
yield(x)
end
n = gets.to_i
factorial(n) do |x|
puts x
end