Automated Market Makers (AMM) in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the constant product in an AMM.

Blockchain / Solidity

constant_product = reserve_a [1] reserve_b

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A/

B*

C-

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of multiplication.

The constant product formula multiplies the reserves of two tokens to keep the product constant.

2fill in blank

medium

Complete the code to calculate the output amount of token B given an input amount of token A.

Blockchain / Solidity

output_amount = reserve_b - (constant_product [1] (reserve_a + input_amount))

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A/

B+

C*

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using multiplication instead of division.

The output amount is calculated by dividing the constant product by the new reserve of token A after adding the input amount.

3fill in blank

hard

Fix the error in the code to correctly update reserves after a swap.

Blockchain / Solidity

reserve_a = reserve_a + [1]
reserve_b = reserve_b - output_amount

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Ainput_amount

Boutput_amount

Cconstant_product

Dfee

Attempts:

3 left

💡 Hint

Common Mistakes

Adding output_amount to reserve_a instead of input_amount.

After a swap, reserve A increases by the input amount of token A.

4fill in blank

hard

Fill both blanks to calculate the fee deducted from the input amount.

Blockchain / Solidity

fee_amount = input_amount [1] fee_rate
net_input = input_amount [2] fee_amount

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A*

B-

C+

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Adding fee instead of subtracting it.

The fee is calculated by multiplying the input amount by the fee rate, then subtracted from the input to get the net input.

5fill in blank

hard

Fill all three blanks to create a dictionary of token reserves with their updated values.

Blockchain / Solidity

updated_reserves = { '[1]': reserve_a, '[2]': reserve_b, '[3]': fee_amount }

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AtokenA

BtokenB

Cfee

Damount

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect or inconsistent keys.

The dictionary keys represent the tokens and fee, mapping to their updated reserve values.