1 files changed, 8 insertions, 3 deletions

diff --git a/index.js b/index.js
index f168d16..6218073 100644
--- a/index.js
+++ b/index.js
@@ -19,7 +19,7 @@ basic.validate_digits = function(s, b) {
 
 // Validate that a base is valid.
 basic.validate_base = function(b){
-	return (b === 0 || b === 1 || b === -1 && (Math.abs(b) % 2) === 0)
+	return (b !== 0 && b !== 1 && b !== -1 && (Math.abs(b) % 2) === 0)
 }
 
 // Convert a string s representing a number in base b
@@ -45,7 +45,7 @@ basic.toString = function (n, b) {
 	var s = ""
 	var dividend, residual
 	while (n) {
-	  remainder = mod(n, b)
+	  remainder = basic.mod(n, b)
     n = Math.floor(n/b)
 		if (remainder) {
 		  n += 1
@@ -55,5 +55,10 @@ basic.toString = function (n, b) {
 	return s
 }
 
-function mod(n,m){ return n-(m * Math.floor(n/m)) }
+// Compute the residual of N mod M
+// Handle negative N and M correctly
+basic.mod = function (n,m){
+	m = Math.abs(m)
+  return n-(m * Math.floor(n/m))
+}