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Recursive Interest Calculator
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#!/usr/bin/env ruby | |
# Copy this file as `recint` (or whatever you want) somewhere in your path and | |
# use it according to the usage notes below! | |
if ARGV.size < 4 | |
puts "Usage: recint <collateral_factor> <supply_apr> <supply_bonus> <borrow_apr> <borrow_bonus>" | |
puts | |
puts " Example - To calculate the net interest on recursively lending this asset:" | |
puts | |
puts " 80% collateral factor (CF)" | |
puts " 2.5% supply APR" | |
puts " 3.7% supply incentive APR" | |
puts " 3.2% borrow APR" | |
puts " 2.1% borrow incentive APR" | |
puts | |
puts " Use this command:" | |
puts | |
puts " recint 80 2.5 3.7 3.2 2.1" | |
puts | |
puts " Output:" | |
puts | |
puts " Base APR: -0.30%" | |
puts " Bonus APR: 26.90%" | |
puts " Total APR: 26.60%" | |
puts | |
exit 1 | |
end | |
# Gather input | |
cf, supply_apr, supply_bonus, borrow_apr, borrow_bonus = ARGV.map(&:to_f) | |
cf /= 100 | |
# Calculate recursive supply and borrow | |
total_supply = 1 / (1 - cf) | |
total_borrow = total_supply * cf | |
# Calculate base apr | |
base_supply_apr = total_supply * supply_apr | |
base_borrow_apr = total_borrow * borrow_apr | |
base_apr = base_supply_apr - base_borrow_apr | |
# Calculate bonus apr | |
bonus_supply_apr = total_supply * supply_bonus | |
bonus_borrow_apr = total_borrow * borrow_bonus | |
bonus_apr = bonus_supply_apr + bonus_borrow_apr | |
# Calculate total apr | |
total_apr = base_apr + bonus_apr | |
def percent(f) | |
'%.2f' % f + '%' | |
end | |
puts "Base APR: #{percent(base_apr)}" | |
puts "Bonus APR: #{percent(bonus_apr)}" | |
puts "Total APR: #{percent(total_apr)}" |
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