Daily Challenge #49 - Dollars and Cents

Today's challenge requires you to create a function that will take a float and return the amount formatted in dollars and cents.

For example: 6.2 becomes $6.20

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This challenge comes from kolohelios on CodeWars. Thank you to CodeWars, who has licensed redistribution of this challenge under the 2-Clause BSD License!

Comments

[Mat-R-Such]

Python

print('$%.2f' %(float(input('Give me money '))))

[peter279k]

Here is the simple solution with PHP:

function format_money(float $amount): string {
    $amounts = explode('.', (string)$amount);
    $moneyFormat = '$%d.%s';

    if (count($amounts) === 1) {
        $floating = '00';

        return sprintf($moneyFormat, $amounts[0], $floating);
    }

    if (strlen($amounts[1]) === 1) {
      $floating = $amounts[1] . '0';

      return sprintf($moneyFormat, $amounts[0], $floating);
    }

    return sprintf($moneyFormat, $amounts[0], substr($amounts[1], 0, 2));
}

[Oleksii Filonenko]

Rust:

fn format_dollars(amount: f64) -> String {
    format!("${:.2}", amount)
}

[Maynard Cabalitan]

Ruby

def maney(amount)
  "$" + '%.2f' % amount.to_f
end

[David J. Davis]

define_method(:us_curr) { |float| format('$%.2f', float.truncate(2)) }
us_curr 2.1256 # => "$2.12"

I thought about this problem from a financial standpoint and didn't like the default ruby or rails options that have been given so far because of how much lost revenue could be happening. Amazon for example has over a billion transactions a day (according to the first link on google). If we use 1.3 billion transactions and assume that the average fractional cents that they give up in a day of transactions is half a cent (.05). That would cost them 6.5 million dollars in lost revenue from giving up fractions of a cent. My solution just trims the number instead of rounding it.

I could see potential for wanting to round up from a business standpoint too, if the calculations are creating a price point for your product in a currency form then by all means you want to round up to still avoid that 6.5 million hit. In which case you would have to adjust the currency function.

This problem can really get interesting depending on your outlook.

[Rafael Acioly]

Python :)

def to_currency(value: float) -> str:
    return "${:.2f}".format(value)

print(to_currency(6.2)) # $6.20

[Seiei Miyagi]

ruby <3

define_method(:format_dollar, &"$%.02f".:%)

[Oleksii Filonenko]

Elixir:

defmodule Day49 do
  def float_to_money(float),
    do: "$#{:io_lib.format("~.2f", [float])}"
end

[Jay]

Rust Function:

fn format_dollar(price: f32) -> String {
    format!("${:.2}", price)
}

[Amin]

My take at the challenge written in Haskell.

toFloat :: String -> Float
toFloat string = read string :: Float

decimalToInt :: Float -> Int
decimalToInt float =
  round
    $ (*) 100
    $ toFloat
    $ take 5
    $ show
    $ float - (fromIntegral $ floor float)

decimalToDollar :: Float -> String
decimalToDollar float =
  "$" 
    ++ (show $ round float)
    ++ "."
    ++ (show $ decimalToInt float)

main :: IO ()
main = do
  putStrLn $ show $ decimalToDollar 6.2 -- "$6.20"
  putStrLn $ show $ decimalToDollar 6.227 -- "$6.23"

Try it online.

For some reason, I get imprecise floating point numbers when grabbing the decimal part of a floating point number in Haskell. I'm pretty new to this language so I must miss something. Feel free to improve my work here.