Simple Intro to Partially Applied Functions in Scala

[Scott Shipp]

If you've ever wondered what people who program in a functional language mean when they say "partially applied function" then I wrote a blog that I hope helps give the answer.

Simple Intro to Partially Applied Functions in Scala

Feedback welcome. I really would love to hear if I was able to make this "simple" as the title suggests.

[chris webster]

Nice one, Scott - thanks for posting!

Not sure if you're planning to follow this up with a look at currying, but here's my take on using curried functions to get rid of all those place-holders:
scala> // Curried function to convert standard currency to base units e.g. dollars to cents scala> def convertCurrencyToUnits(unitsPer: Int) = (currAmount: BigDecimal) => currAmount * unitsPer convertCurrencyToUnits: (unitsPer: Int)BigDecimal => scala.math.BigDecimal scala> // Function to convert dollars to cents scala> def dollarsToCents = convertCurrencyToUnits(100) dollarsToCents: BigDecimal => scala.math.BigDecimal scala> // Function to convert old UK pounds to pence scala> def oldPoundsToPence = convertCurrencyToUnits(240) oldPoundsToPence: BigDecimal => scala.math.BigDecimal scala> // Making change... scala> def changeForDollars(dollars: BigDecimal, coin: Int) = dollarsToCents(dollars) / coin changeForDollars: (dollars: BigDecimal, coin: Int)scala.math.BigDecimal scala> def changeForOldPounds(pounds: BigDecimal, coin: Int) = oldPoundsToPence(pounds) / coin changeForOldPounds: (pounds: BigDecimal, coin: Int)scala.math.BigDecimal scala> // Try them out: scala> // How many nickels in $1.50? scala> changeForDollars(1.50, 5) res0: scala.math.BigDecimal = 30.0 scala> // How many shillings (12 pence) in £3? scala> changeForOldPounds(3, 12) res1: scala.math.BigDecimal = 60 // No need to remember how many pennies in a shilling: scala> def shillingsForOldPounds = (pounds: BigDecimal) => changeForOldPounds(pounds, 12) shillingsForOldPounds: BigDecimal => scala.math.BigDecimal scala> shillingsForOldPounds(3) res2: scala.math.BigDecimal = 60
Strictly speaking, some of those functions could be function values, but I'm trying to keep it simple, as you did!

[Scott Shipp]

Sweet! Thanks for checking it out and thanks for the suggestion. That's a great idea!