fix: encapsulate natSafeMath.isGTE

Agoric · Nov 5, 2020 · 658c223 · 658c223
1 parent 738406d
commit 658c223
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Showing 3 changed files with 8 additions and 6 deletions.
diff --git a/packages/zoe/src/contractSupport/safeMath.js b/packages/zoe/src/contractSupport/safeMath.js
@@ -10,4 +10,5 @@ export const natSafeMath = harden({
   multiply: (x, y) => Nat(x * y),
   floorDivide: (x, y) => Nat(Math.floor(x / y)),
   ceilDivide: (x, y) => Nat(Math.ceil(x / y)),
+  isGTE: (x, y) => x >= y,
 });
diff --git a/packages/zoe/src/contractSupport/statistics.js b/packages/zoe/src/contractSupport/statistics.js
@@ -3,6 +3,7 @@
  * @typedef {Object} TypedMath
  * @property {(a: T, b: T) => T} add
  * @property {(a: T, b: T) => T} divide
+ * @property {(a: T, b: T) => boolean} isGTE
  */
 
 /**
@@ -15,12 +16,12 @@
  */
 export const calculateMedian = (samples, math) => {
   const sorted = samples.sort((a, b) => {
-    if (a < b) {
+    if (!math.isGTE(a, b)) {
       return -1;
-    } else if (a === b) {
-      return 0;
+    } else if (!math.isGTE(b, a)) {
+      return 1;
     }
-    return 1;
+    return 0;
   });
 
   if (sorted.length === 0) {

diff --git a/packages/zoe/src/contracts/priceAggregator.js b/packages/zoe/src/contracts/priceAggregator.js
@@ -12,7 +12,7 @@ import {
 import '../../exported';
 import './exported';
 
-const { add, multiply, floorDivide, ceilDivide } = natSafeMath;
+const { add, multiply, floorDivide, ceilDivide, isGTE } = natSafeMath;
 
 /**
  * This contract aggregates price values from a set of oracles and provides a
@@ -163,7 +163,7 @@ const start = async zcf => {
   const updateQuote = async (samples, timestamp) => {
     const median = calculateMedian(
       samples.filter(sample => sample > 0 && Number.isSafeInteger(sample)),
-      { add, divide: floorDivide },
+      { add, divide: floorDivide, isGTE },
     );
 
     // console.error('found median', median, 'of', samples);