mk2taiga / simple-calc

Let's implement a dead simple command line calculator from scratch!

simple-calc

Let's implement a dead simple command line calculator from scratch!

Introduction

Your goal is to implement a very simple command line calculator from scratch in Go. Write an arithmetic expression parser on your own, without using any existing parser libraries.

Restrictions

• Do not use go/* packages such as go/parser or go/scanner in the standard library.
• Do not use text/scanner package in the standard library.
• Do not use any third-party libraries.
• Do not invoke any external processes, for example using os/exec package.

Steps to implement

The recommended way is TDD style:

1. Run go test command and make sure all tests are passed (actually no tests are run).
2. Remove t.Skip() line within TestInt function in main_test.go.
3. Run go test command and make sure TestInt fails.
4. Implement calc function in main.go so that all the tests that failed above are passed.
5. If all tests have been passed, then remove t.Skip() line within TestAddSub function in main_test.go.
6. Run go test command and make sure TestAddSub fails.
7. Update calc function in main.go so that all the tests that failed above are passed.
8. If all tests have been passed, then remove t.Skip() line within TestMulDiv function in main_test.go.
9. In the same way, update calc function until all tests in main_test.go have been passed after removing all t.Skip() lines.

Eventually, your calculator should be able to correctly calculate complex arithmetic expressions like this:

$ go build
$ ./simple-calc '(8 - 5) * (-2) + (-9 + 8) * (5 - 7) - 12 / (22 - 16) * (-3)'
2