Daily Challenge #49 - Dollars and Cents

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Daily Challenge (137 Part Series)

1) Daily Challenge #1 - String Peeler 2) Daily Challenge #2 - String Diamond 3 ... 135 3) Daily Challenge #3 - Vowel Counter 4) Daily Challenge #4 - Checkbook Balancing 5) Daily Challenge #5 - Ten Minute Walk 6) Daily Challenge #6 - Grandma and her friends 7) Daily Challenge #7 - Factorial Decomposition 8) Daily Challenge #8 - Scrabble Word Calculator 9) Daily Challenge #9 - What's Your Number? 10) Daily Challenge #10 - Calculator 11) Daily Challenge #11 - Cubic Numbers 12) Daily Challenge #12 - Next Larger Number 13) Daily Challenge #13 - Twice Linear 14) Daily Challenge #14 - Square into Squares 15) Daily Challenge #15 - Stop gninnipS My sdroW! 16) Daily Challenge #16 - Number of People on the Bus 17) Daily Challenge #17 - Double Trouble 18) Daily Challenge #18 - Triple Trouble 19) Daily Challenge #19 - Turn numbers into words 20) Daily Challenge Post #20 - Number Check 21) Daily Challenge #21 - Human Readable Time 22) Daily Challenge #22 - Simple Pig Latin 23) Daily Challenge #23 - Morse Code Decoder 24) Daily Challenge #24 - Shortest Step 25) Daily Challenge #25 - Double Cola 26) Daily Challenge #26 - Ranking Position 27) Daily Challenge #27 - Unlucky Days 28) Daily Challenge #28 - Kill the Monster! 29) Daily Challenge #29 - Xs and Os 30) Daily Challenge #30 - What is the price? 31) Daily Challenge #31 - Count IPv4 Addresses 32) Daily Challenge #32 - Hide Phone Numbers 33) Daily Challenge #33 - Did you mean...? 34) Daily Challenge #34 - WeIrD StRiNg CaSe 35) Daily Challenge #35 - Find the Outlier 36) Daily Challenge #36 - Let's go for a run! 37) Daily Challenge #37 - Name Swap 38) Daily Challenge #38 - Middle Name 39) Daily Challenge #39 - Virus 40) Daily Challenge #40 - Counting Sheep 41) Daily Challenge #41 - Greed is Good 42) Daily Challenge #42 - Caesar Cipher 43) Daily Challenge #43 - Boardgame Fight Resolver 44) Daily Challenge #44 - Mexican Wave 45) Daily Challenge #45 - Change Machine 46) Daily Challenge #46 - ??? 47) Daily Challenge #47 - Alphabets 48) Daily Challenge #48 - Facebook Likes 49) Daily Challenge #49 - Dollars and Cents 50) Daily Challenge #50 - Number Neighbor 51) Daily Challenge #51 - Valid Curly Braces 52) Daily Challenge #52 - Building a Pyramid 53) Daily Challenge #53 - Faro Shuffle 54) Daily Challenge #54 - What century is it? 55) Daily Challenge #55 - Building a Pile of Cubes 56) Daily Challenge #56 - Coffee Shop 57) Daily Challenge #57 - BMI Calculator 58) Daily Challenge #58 - Smelting Iron Ingots 59) Daily Challenge #59 - Snail Sort 60) Daily Challenge #60 - Find the Missing Letter 61) Daily Challenge #61 - Evolution Rate 62) Daily Challenge #62 - Josephus Survivor 63) Daily Challenge #63- Two Sum 64) Daily Challenge #64- Drying Potatoes 65) Daily Challenge #65- A Disguised Sequence 66) Daily Challenge #66- Friend List 67) Daily Challenge #67- Phone Directory 68) Daily Challenge #68 - Grade Book 69) Daily Challenge #69 - Going to the Cinema 70) Daily Challenge #70 - Pole Vault Competition Results 71) Daily Challenge #71 - See you next Happy Year 72) Daily Challenge #72 - Matrix Shift 73) Daily Challenge #73 - ATM Heist 74) Daily Challenge #74 - Free Pizza 75) Daily Challenge #75 - Set Alarm 76) Daily Challenge #76 - Bingo! (or not...) 77) Daily Challenge #77 - Bird Mountain 78) Daily Challenge #78 - Number of Proper Fractions with Denominator d 79) Daily Challenge #79 - Connect Four 80) Daily Challenge #80 - Longest Vowel Change 81) Daily Challenge #81 - Even or Odd 82) Daily Challenge #82 - English Beggars 83) Daily Challenge #83 - Deodorant Evaporator 84) Daily Challenge #84 - Third Angle of a Triangle 85) Daily Challenge #85 - Unwanted Dollars 86) Daily Challenge #86 - Wouldn't, not Would. 87) Daily Challenge #87 - Pony Express 88) Daily Challenge #88 - Recursive Ninjas 89) Daily Challenge #89 - Extract domain name from URL 90) Daily Challenge #90 - One Step at a Time 91) Daily Challenge #91 - Bananas 92) Daily Challenge #92 - Boggle Board 93) Daily Challenge #93 - Range Extraction 94) Daily Challenge #94 - Last Digit 95) Daily Challenge #95 - CamelCase Method 96) Daily Challenge #96 - Easter Egg Crush Test 97) Daily Challenge #97 - Greed is Good 98) Daily Challenge #98 - Make a Spiral 99) Daily Challenge #99 - Balance the Scales 100) Daily Challenge #100 - Round Up 101) Daily Challenge #101 - Parentheses Generator 102) Daily Challenge #102 - Pentabonacci 103) Daily Challenge #103 - Simple Symbols 104) Daily Challenge #104 - Matrixify 105) Daily Challenge #105 - High-Sum Matrix Drop 106) Daily Challenge #106 - Average Fuel Consumption 107) Daily Challenge #107 - Escape the Mines 108) Daily Challenge #108 - Find the Counterfeit Coin 109) Daily Challenge #109 - Decorate with Wallpaper 110) Daily Challenge #110 - Love VS. Friendship 111) Daily Challenge #111 - 99 Bottles of Beer 112) Daily Challenge #112 - Functions of Integers on the Cartesian Plane 113) Daily Challenge #113 - Iterative Rotation Cipher 114) Daily Challenge #114 - Speed Control 115) Daily Challenge #115 - Look and Say Sequence 116) Daily Challenge #116 - Shortest Knight Path 117) Daily Challenge #117 - MinMinMax 118) Daily Challenge #118 - Reversing a Process 119) Daily Challenge #119 - Adding Big Numbers 120) Daily Challenge #120 - Growth of a Population 121) Daily Challenge #121 - Who has the most money? 122) Daily Challenge #122 - Clockwise Spirals 123) Daily Challenge #123 - Curry me Softly 124) Daily Challenge #124 - Middle Me 125) Daily Challenge #125 - 23 Matches or More 126) Daily Challenge #126 - The Supermarket Line 127) Daily Challenge #127 - Playing with Passphrases 128) Daily Challenge #128 - Blackjack Scorer 129) Daily Challenge #129 - Clay Pigeon Shooting 130) Daily Challenge #130 - GCD Sum 131) Daily Challenge #131 - Remove Anchor from URL 132) Daily Challenge #132 - Is my friend cheating? 133) Daily Challenge #133 - Suitcase Packing 134) Daily Challenge #134 - Rice and Chessboard Problem 135) Daily Challenge #135 - The Wide Mouthed Frog! 136) Daily Challenge #136 - The Deaf Rats of Hamelin 137) Daily Challenge #137 - Help the Bookseller

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


Want to propose a challenge idea for a future post? Email yo+challenge@dev.to with your suggestions!

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

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Here we go!

f=a=>`$${a.toFixed`2`}`;

And the results:

f(.4); // "$0.40"
f(0); // "$0.00"
f(6.2); // "$6.20"

And how about some Intl?

f=a=>new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' }).format(a)

Which does a bit more, like adding commas:

f(.4); // "$0.40"
f(0); // "$0.00"
f(6.2); // "$6.20"
f(100000000.1234); // "$100,000,000.12"
 

Hello, I am surprised, you can call a function with ``. How come is it working?

 

ES6 added this functionality, called Tagged Template! A few examples can be found here: wesbos.com/tagged-template-literals/

 

Sometimes I just think about Rails method that does a very specific thing, type it out in console and it works

number_to_currency(number)
 
const formatDollars = money => `$${money.toFixed(2)}`;


`
love js

 

Mind rounding "errors":

formatDollars(.126)
> '$0.13'

Same happens in python:

print(f"{123.126:.2f}")
123.13
 

It rounded up, though, so is that an error? It seems like expected behavior to me.

 

Go - with tests as usual

fun fact - this was the first time I wrote anything using Vim

dollars.go

package dollars

import (
    "fmt"
)

// Dollars returns the string representation of a float as a dollar amount
func Dollars(amount float64) string {
    return fmt.Sprintf("$%.2f", amount)
}

dollars_test.go

package dollars

import (
    "testing"
)

var testCases = []struct {
    description string
    input       float64
    expected    string
}{
    {
        "only cents",
        .04,
        "$0.04",
    },
    {
        "only dollars",
        3,
        "$3.00",
    },
    {
        "cents & dollars",
        3.14,
        "$3.14",
    },
    {
        "amounts with more than two decimal places round to the nearest cent",
        4.478,
        "$4.48",
    },

}

func TestDollars(t *testing.T) {
    for _, test := range testCases {
        if result := Dollars(test.input); result != test.expected {
            t.Fatalf("FAILED: %s - Dollars(%f): %s, expected %s \n", test.description, test.input, result, test.expected)
        }
        t.Logf("PASS: %s \n", test.description)
    }
}

 

I'm not sure, but I think that "Sprintf" rounds to nearest integer.
Try with a value like 3.149 if still returns 3.14 or 3.15

 

Yeah it rounds to the nearest cent in this case, the question becomes then do we want it to work that way, or do we say "Hey you don't have a full cent" so it always rounds down?

 

Added additional test case to clarify current rounding behavior.

 

With miles separator too:

const formatMoney = money => [...`$${money .toFixed(2)}`]
  .reverse()
  .flatMap((c, i) => (c != '.' && c != '$' && i > 3 && i % 3 == 0) ? [',', c]: [c])
  .reverse()
  .join('');

// formatMoney(12123123123131232.000) => $12,123,123,123,131,232.00
 

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.

 

Rust Function:

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

 

ruby <3

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

Ruby

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

Elixir:

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

In Ruby:

def float_to_currency(float)
  format('$%.2f', float)
end
 

Python :)

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

print(to_currency(6.2)) # $6.20
 

Rust:

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

Here is the python code

num=float(input())
print("${:,.2f}".format(num))

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