Skip to content

Exercise 15: Start a project

Aim: run and test from a project directory, then separate an exported function from the application. Keep this project beside your exercise files.

Create and inspect

From your fibber-hardway directory:

fibc new tally
cd tally
fibc run src/main.fib
fibc test
fibc deps tree

Inspect deps.fib, src/ and the generated spec before editing anything. deps.fib declares the project's source paths and dependencies. Keep commands in this directory so project discovery finds it. Keep a generated deps.lock in version control when dependencies are resolved and locked.

Type and predict

Replace src/main.fib with this program:

(ns main (:require [fib.string :as text]))
(defun main () -> i64
  (do
    (println (text/join ", " ["read" "count" "report"]))
    0))
Check your prediction 
read, count, report
0

Change it

  1. Run the replacement main and run the generated spec. Inspect what the spec actually tests; passing that spec does not prove your new main is correct.
  2. Create src/tally/price.fib with namespace tally.price. Move exercise 14's total function there, preserving its signature. A library module needs no main.
  3. Copy exercise 14 into specs/price-spec.fib. Remove its inline total definition, require [tally.price :as price] in both main and that spec, and call price/total. Keep the scenarios and expected values. Run main, fibc test specs/price-spec.fib, then fibc test to check discovery too.

The mapping is literal: tally.price maps to tally/price.fib under a source root, here src. Ordinary public declarations are available through the module alias. Use the namespace guide for details.

Break and repair

Rename the module file to prices.fib without changing the namespace or require. Observe the missing-module diagnostic. Repair the path/declaration agreement. Then run from the parent directory and explain why relative file paths and project discovery can differ. Return to the project directory before continuing.

Checkpoint

Draw the path from the project's source root to tally.price. Explain what deps tree tells you, and what it cannot tell you about whether your arithmetic is correct. You now have a place to build the final command.

← Behaviour specs · Course · Capstone →