BhawickJain / expression-kata-with-melissa

Expression Tree Kata scaffolding, utilities, and solutions

flowchart TD
    A[+] --> B[*]
    A --> C(6)
    B --> D(12)
    B --> E(3)

This repo contains various resources for the exercise: Evaluate calculator expressions.

If you want some scaffolding you can work from src/task/expressions.ts and use or re-write tests in src/task/expressions-test.ts

There are also some solutions in src/solutions

Bonus: generating a diagram

A function has been provided which will take an expression tree and generate the necessary graphviz dot-language code to make a directed graph. Just paste the result into graphviz - e.g. at https://dreampuf.github.io/GraphvizOnline/

See src/solutions/generateGraph.ts

Bonus: parsing from string to expression tree

For the curious, a simple parser has been provided which will create an expression tree from a string. See: src/solutions/parser.test.ts

You use it by calling parseExpression(str)

Example:

parseExpression("(+ (/ 5 (* 2 5)) (- 5 4))");

//should yield

{
  op: "add",
  a: { op: "divide", a: 5, b: { op: "multiply", a: 2, b: 5 } },
  b: { op: "subtract", a: 5, b: 4 },
}