From: Scott Worley <scottworley@scottworley.com>
Date: Thu, 23 May 2019 20:18:39 +0000 (-0700)
Subject: Handle empty tax table
X-Git-Tag: v1.0~16
X-Git-Url: http://git.scottworley.com/inverse-tax/commitdiff_plain/1c6e40691d86539d80018aa8fc495272b900c4c4

Handle empty tax table
---

diff --git a/tax.js b/tax.js
index 0d94200..d26db5f 100644
--- a/tax.js
+++ b/tax.js
@@ -49,6 +49,8 @@ function merge_tax_tables(t1, t2) {
 }
 
 function invert(table) {
+  if (table.length == 0) return x => x;
+
   // Here we solve
   //   net = m * gross + b
   // for gross:
diff --git a/tax.test.js b/tax.test.js
index 19597fb..48f2e0d 100644
--- a/tax.test.js
+++ b/tax.test.js
@@ -47,6 +47,7 @@ test("merge tax tables", () => {
 });
 
 test("invert", () => {
+  assert.strictEqual(invert([                  ])(10), 10);
   assert.strictEqual(invert([[ 0, Infinity, .1]])( 9), 10);
   assert.strictEqual(invert([[10, Infinity, .1]])(19), 20);
   assert.strictEqual(invert([[0, 100, .1], [100, Infinity, .2]])(170), 200);