Hackerrank Blocks Solution
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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 and .
The yield
statement invokes the block with parameters and , and executes it.
Task
You are given a partially complete code. Your task is to fill in the blanks (_______
).
The factorial method computes: n!
{ x x x }.
Solution in ruby
Approach 1.
def factorial
yield
end
n = gets.to_i
factorial do
puts (1..n).inject(:*)
end
Approach 2.
def factorial
yield
end
n = gets.to_i
factorial do
puts (1..n).reduce(:*)
end
Approach 3.
def factorial
yield
end
n = gets.to_i
factorial do
puts (1..n).inject(:*)
end