Collection functions (length, flatten, merge) in Terraform - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of length function on a list?

Given the Terraform expression length(["apple", "banana", "cherry"]), what is the output?

Terraform

length(["apple", "banana", "cherry"])

A 2

B 3

C 0

D Error

💡 Hint

Count the number of items inside the list.

The length function returns the number of elements in the list. Here, there are three fruits, so the output is 3.

❓ query_result

intermediate

What does flatten do to nested lists?

What is the result of flatten([[1, 2], [3, 4], [5]]) in Terraform?

Terraform

flatten([[1, 2], [3, 4], [5]])

A Error

B [[1, 2], [3, 4], [5]]

C [1, 2, 3, 4, 5]

D [1, [2, 3], 4, 5]

💡 Hint

Flatten removes one level of nested lists.

The flatten function merges all inner lists into a single list, so the output is a flat list of all elements.

📝 Syntax

advanced

Which merge expression correctly combines two maps?

Select the Terraform expression that correctly merges two maps {a = 1, b = 2} and {b = 3, c = 4} with the second map overriding keys from the first.

A merge({a = 1, b = 2} + {b = 3, c = 4})

B merge({a = 1, b = 2}, {b: 3, c: 4})

C merge([{a = 1, b = 2}, {b = 3, c = 4}])

D merge({a = 1, b = 2}, {b = 3, c = 4})

💡 Hint

Use merge with two separate map arguments.

The merge function takes multiple maps as separate arguments and combines them. Option D is the correct syntax.

❓ optimization

advanced

Optimizing nested flatten calls

Given a nested list [[[1], [2, 3]], [[4]]], which expression efficiently flattens it into a single list [1, 2, 3, 4]?

A flatten(flatten([[[1], [2, 3]], [[4]]]))

B flatten([1, 2, 3, 4])

C flatten(flatten(flatten([[[1], [2, 3]], [[4]]])))

D flatten([[[1], [2, 3]], [[4]]])

💡 Hint

Use flatten twice to remove two levels of nesting.

The list has three levels of nesting. Using flatten twice removes two levels, resulting in a flat list.

🧠 Conceptual

expert

What is the length of a merged map?

If you merge two maps {x = 10, y = 20} and {y = 30, z = 40}, what is the length of the resulting map?

Terraform

length(merge({x = 10, y = 20}, {y = 30, z = 40}))

A 3

B 4

C 2

D Error

💡 Hint

Keys that appear in both maps are overridden, not duplicated.

The merged map has keys x, y, and z. The key y from the second map overrides the first. So total keys are 3.