From c38752820cf44daee6037e9c57eb6d38d5f00d07 Mon Sep 17 00:00:00 2001
From: Christian Lawson-Perfect <christianperfect@gmail.com>
Date: Tue, 16 Jan 2024 09:39:38 +0000
Subject: [PATCH] siground rounds to 0 when within 1e-15.
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`cos(pi/2)`, for example, is not exactly 0 due to floating point
rounding error - it's 6.123233995736766e-17.

This commit changes `math.siground` to round a to 0 when `isclose(a,0)`,
which is true if it's ±1e-15.
---
 runtime/scripts/math.js | 3 +++
 tests/jme-runtime.js    | 3 +++
 tests/jme/jme-tests.mjs | 2 ++
 tests/numbas-runtime.js | 3 +++
 4 files changed, 11 insertions(+)

diff --git a/runtime/scripts/math.js b/runtime/scripts/math.js
index a0afa5aed..10a3c2c6a 100644
--- a/runtime/scripts/math.js
+++ b/runtime/scripts/math.js
@@ -1227,6 +1227,9 @@ var math = Numbas.math = /** @lends Numbas.math */ {
         if(a.complex) {
             return math.complex(math.siground(a.re,b),math.siground(a.im,b));
         } else {
+            if(math.isclose(a,0)) {
+                return 0;
+            }
             return parseFloat(a.toPrecision(b))
         }
     },
diff --git a/tests/jme-runtime.js b/tests/jme-runtime.js
index 748122105..100314ef2 100644
--- a/tests/jme-runtime.js
+++ b/tests/jme-runtime.js
@@ -3448,6 +3448,9 @@ var math = Numbas.math = /** @lends Numbas.math */ {
         if(a.complex) {
             return math.complex(math.siground(a.re,b),math.siground(a.im,b));
         } else {
+            if(math.isclose(a,0)) {
+                return 0;
+            }
             return parseFloat(a.toPrecision(b))
         }
     },
diff --git a/tests/jme/jme-tests.mjs b/tests/jme/jme-tests.mjs
index c9e130f29..08487c083 100644
--- a/tests/jme/jme-tests.mjs
+++ b/tests/jme/jme-tests.mjs
@@ -1011,6 +1011,8 @@ Numbas.queueScript('jme_tests',['qunit','jme','jme-rules','jme-display','jme-cal
             assert.equal(evaluate('ceil('+expr+')').value, c, 'ceil('+expr+')');
             deepCloseEqual(assert,evaluate('fract('+expr+')'), evaluate(fr), 'fract('+expr+')');
         });
+
+        assert.equal(evaluate('siground(cos(pi/2),3)').value, 0, 'siground(cos(pi/2))');
     });
 
     QUnit.test('Currency',function(assert) {
diff --git a/tests/numbas-runtime.js b/tests/numbas-runtime.js
index bcebc9684..da557f209 100644
--- a/tests/numbas-runtime.js
+++ b/tests/numbas-runtime.js
@@ -3449,6 +3449,9 @@ var math = Numbas.math = /** @lends Numbas.math */ {
         if(a.complex) {
             return math.complex(math.siground(a.re,b),math.siground(a.im,b));
         } else {
+            if(math.isclose(a,0)) {
+                return 0;
+            }
             return parseFloat(a.toPrecision(b))
         }
     },