Chapter 7: money, typed

Chapter 7's Receipt adds up a shopping basket in pounds: prices written with the #GBP suffix, multiplied by whole quantities, summed and printed in en_GB format. The IDE writes the program's shell; the amounts are yours to type. To play it in the IDE: Help > Lessons > Getting Started with EK9…, or ek9 -ide -lesson book-receipt.

What you'll build

The lesson builds this program from a file holding only its module line - the finished file, as the book prints it.

#!ek9
defines module book.receipt

  defines program

    Receipt()
      stdout <- Stdout()
      enGB <- Locale("en_GB")

      applePrice <- 0.35#GBP
      breadPrice <- 1.10#GBP
      milkPrice <- 0.85#GBP

      apples <- 6
      loaves <- 2
      bottles <- 1

      appleLine <- applePrice * apples
      breadLine <- breadPrice * loaves
      milkLine <- milkPrice * bottles

      total <- appleLine + breadLine + milkLine

      stdout.println(`Apples  x${apples}   ${enGB.format(appleLine)}`)
      stdout.println(`Bread   x${loaves}   ${enGB.format(breadLine)}`)
      stdout.println(`Milk    x${bottles}   ${enGB.format(milkLine)}`)
      stdout.println(`Total        ${enGB.format(total)}`)

Step 1: The program's shell

Choose Code > New Construct > Program…

Receipt is the program's name. Type it and choose Preview.

The preview shows Receipt about to be written. Choose Apply.

The tool leaves no blank line before the program: select the Receipt() line and, above it, type the one the book opens with. Saves when typed.

Step 2: The body, typed

Select the stub, from ready <- true down to its //AI line, and type the body exactly as the chapter shows it. Saves when typed.

Step 3: Run it

Choose Run > Run Program…

The project's only program is already chosen. Choose Run.

Apples x6 £2.10, Bread x2 £2.20, Milk x1 £0.85, Total £5.15. Choose Close.

The result

Receipt.ek9 now reads exactly as chapter 7 of Getting Started with EK9 shows it: Money times an Integer is Money, Money plus Money is Money, and the Locale formats each as pounds.

Where this lesson comes from

• For AI assistants - the MCP tool ek9_add_program.

In the EK9 reference: EK9 Basics