WIP: math parser

2kyu/evaluate-mathematical-expression/description.md

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+Instructions
+Given a mathematical expression as a string you must return the result as a number.
+
+Numbers
+Number may be both whole numbers and/or decimal numbers. The same goes for the returned result.
+
+Operators
+You need to support the following mathematical operators:
+
+Multiplication *
+Division / (as floating point division)
+Addition +
+Subtraction -
+Operators are always evaluated from left-to-right, and * and / must be evaluated before + and -.
+
+Parentheses
+You need to support multiple levels of nested parentheses, ex. (2 / (2 + 3.33) * 4) - -6
+
+Whitespace
+There may or may not be whitespace between numbers and operators.
+
+An addition to this rule is that the minus sign (-) used for negating numbers and parentheses will never be separated by whitespace. I.e all of the following are valid expressions.
+
+1-1    // 0
+1 -1   // 0
+1- 1   // 0
+1 - 1  // 0
+1- -1  // 2
+1 - -1 // 2
+1--1   // 2
+
+6 + -(4)   // 2
+6 + -( -4) // 10
+And the following are invalid expressions
+
+1 - - 1    // Invalid
+1- - 1     // Invalid
+6 + - (4)  // Invalid
+6 + -(- 4) // Invalid
+Validation
+You do not need to worry about validation - you will only receive valid mathematical expressions following the above rules.

2kyu/evaluate-mathematical-expression/solution.ts

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+
+type Token = number | '+' | '-' | '*' | '/' | '(' | ')';
+
+
+
+type ASTNode = {
+  type: string,
+}
+
+type OperatorNode = {
+  type: 'operator',
+  value: '+' | '-' | '*' | '/',
+  left: ASTNode,
+  right: ASTNode,
+}
+
+type NumberNode = {
+  type: 'number',
+  value: number,
+}
+
+type GroupNode = {
+  type: 'group',
+  value: ASTNode,
+}
+
+type NegationNode = {
+  type: 'negation',
+  value: ASTNode,
+}
+
+export function calc(expression: string): number {
+  // evaluate `expression` and return result
+  return 0;
+}

2kyu/evaluate-mathematical-expression/tests.ts

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+import { calc } from './solution';
+import { expect } from "chai";
+
+var tests: [string, number][] = [
+  ['1+1', 2],
+  ['1 - 1', 0],
+  ['1* 1', 1],
+  ['1 /1', 1],
+  ['-123', -123],
+  ['123', 123],
+  ['2 /2+3 * 4.75- -6', 21.25],
+  ['12* 123', 1476],
+  ['2 / (2 + 3) * 4.33 - -6', 7.732],
+];
+
+describe("calc", function() {
+  it("should evaluate correctly", () => {
+    tests.forEach(function(m) {
+      var x = calc(m[0]);
+      var y = m[1];
+      expect(x).to.equal(y, 'Expected: "' + m[0] + '" to be ' + y + ' but got ' + x);
+    });
+  });
+});