Closures and variable binding in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a closure that returns a lambda adding a fixed number.

Ruby

def make_adder(n)
  return ->(x) { x [1] n }
end

add_five = make_adder(5)
puts add_five.call(10)

Drag options to blanks, or click blank then click option'

A+

B-

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition.

Forgetting to use the lambda syntax.

The lambda adds the fixed number n to the argument x. So the operator must be +.

2fill in blank

medium

Complete the code to capture the variable correctly inside the closure.

Ruby

def make_multipliers
  multipliers = []
  3.times do |i|
    multipliers << ->(x) { x * [1] }
  end
  multipliers
end

procs = make_multipliers
puts procs[0].call(2)

Drag options to blanks, or click blank then click option'

A2

B3

Cx

Di

Attempts:

3 left

💡 Hint

Common Mistakes

Using a fixed number instead of the loop variable.

Using the wrong variable name.

The variable i is captured by the lambda to multiply x by i. This shows variable binding in closures.

3fill in blank

hard

Fix the error in the closure to correctly capture the loop variable value.

Ruby

def make_procs
  procs = []
  3.times do |i|
    val = i
    procs << -> { val [1] 1 }
  end
  procs
end

procs = make_procs
puts procs[1].call

Drag options to blanks, or click blank then click option'

A-

B+

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition.

Not capturing the variable correctly.

The lambda adds 1 to the captured val. Using + fixes the closure to use the correct value.

4fill in blank

hard

Fill both blanks to create a closure that captures the current loop variable and multiplies it.

Ruby

def make_funcs
  funcs = []
  4.times do |i|
    funcs << ->(x) { (x [1] i) [2] 2 }
  end
  funcs
end

funcs = make_funcs
puts funcs[2].call(3)

Drag options to blanks, or click blank then click option'

A*

B+

C**

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using multiplication instead of addition.

Using subtraction instead of exponentiation.

The closure adds i to x and then raises the result to the power of 2 using **.

5fill in blank

hard

Fill all three blanks to create a closure that filters and transforms a hash based on variable binding.

Ruby

def filter_transform(data)
  result = data.select { |k, v| v [1] 10 }
               .map { |k, v| [k.[2], v [3] 5] }
  result.to_h
end

input = {"a" => 12, "b" => 8, "c" => 15}
output = filter_transform(input)
puts output

Drag options to blanks, or click blank then click option'

A>

Bupcase

C-

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using less than instead of greater than for filtering.

Not transforming keys or values correctly.

The code selects key-value pairs where the value is greater than 10, then transforms keys to uppercase and subtracts 5 from values.