--- /dev/null
+"use strict";
+
+function parse_table(as_text) {
+ function parse_line(line) {
+ return line.trim().split(' ').filter(x => x !== '').map(x => parseFloat(x));
+ }
+ return as_text.trim().split('\n').map(parse_line);
+}
+
+function parse_tax_table(as_text) {
+ return parse_table(as_text).map(([start, rate], i, table) =>
+ [start, i < table.length - 1 ? table[i+1][0] : Infinity, rate / 100.0]);
+}
+
+function sum(nums) {
+ return nums.reduce((total, num) => total + num, 0);
+}
+
+function tax(table, income) {
+ return sum(table.map(([start, end, rate]) =>
+ Math.max(0, Math.min(income, end) - start) * rate));
+}
+
+function apply_deductible(table, deductible) {
+ return table.map(([start, end, rate]) => [start + deductible, end + deductible, rate]);
+}
+
+function merge_tax_tables(t1, t2) {
+ if (t1.length == 0) return t2;
+ if (t2.length == 0) return t1;
+ [start1, end1, rate1] = t1[0];
+ [start2, end2, rate2] = t2[0];
+ if (start1 == start2) {
+ if (end1 == end2) {
+ return [[start1, end1, rate1 + rate2]].concat(merge_tax_tables(t1.slice(1), t2.slice(1)));
+ }
+ if (end1 < end2) {
+ return [[start1, end1, rate1 + rate2]].concat(merge_tax_tables(t1.slice(1), [[end1, end2, rate2]].concat(t2.slice(1))));
+ }
+ return merge_tax_tables(t2, t1);
+ }
+ if (start1 < start2) {
+ if (end1 <= start2) {
+ return [t1[0]].concat(merge_tax_tables(t1.slice(1), t2));
+ }
+ return [[start1, start2, rate1]].concat(merge_tax_tables([[start2, end1, rate1]].concat(t1.slice(1)), t2));
+ }
+ return merge_tax_tables(t2, t1);
+}
--- /dev/null
+"use strict";
+
+var assert = require('assert');
+
+function test(description, f) {
+ f();
+}
+
+function near(a, b, epsilon = 1e-6) {
+ return Math.abs(a - b) < epsilon;
+}
+
+test("parse tax table", () => {
+ const parsed = parse_tax_table(' 1 2\n10 4\n');
+ assert.strictEqual(parsed.length, 2);
+ assert.deepStrictEqual(parsed[0], [1, 10, .02]);
+ assert.deepStrictEqual(parsed[1], [10, Infinity, .04]);
+});
+
+test("sum", () => {
+ assert.strictEqual(sum([]), 0);
+ assert.strictEqual(sum([7]), 7);
+ assert.strictEqual(sum([100, 1, 10]), 111);
+});
+
+test("tax", () => {
+ assert.strictEqual(tax([[10, 100, .01], [100, Infinity, .1]], 150), 5.9);
+ assert.ok(near(tax([[10, 100, .01], [100, Infinity, .1]], 150), 5.9));
+});
projects / inverse-tax / commitdiff