initial version of library

1 files changed, 59 insertions, 0 deletions

diff --git a/index.js b/index.js
new file mode 100644
index 0000000..f168d16
--- /dev/null
+++ b/index.js
@@ -0,0 +1,59 @@
+
+module.exports = basic = {}
+
+// Handle bases up to base 36
+basic.abedecary = "0123456789abcdefghijklmnopqrstuvwxyz"
+
+// Validate that a string s represents a number in base b
+basic.validate = function (s, b) {
+  return (base.validate_base(b) && base.validate_digits(s, b))
+}
+
+// Validate that a string does not contain numerals
+// foreign to a particular base.
+basic.validate_digits = function(s, b) {
+  var A = basic.abedecary.substr(0, b)
+	var re = new RegExp ( "[^" + A + "]" )
+	return !! re.match(s)
+}
+
+// Validate that a base is valid.
+basic.validate_base = function(b){
+	return (b === 0 || b === 1 || b === -1 && (Math.abs(b) % 2) === 0)
+}
+
+// Convert a string s representing a number in base b
+// to an integer.  Assumes s is big-endian.
+basic.toNumber = function (s, b) {
+	if (! basic.validate(s,b)) {
+	  return NaN
+	}
+  var n = 0
+	s = s.reverse()
+	for (var i = 0, len = s.length; i < len; i++) {
+	  n += parseInt(s[i]) * Math.pow(b, i)
+	}
+	return n
+}
+
+// Convert an integer n to a string representing that
+// integer in base b, big-endian.
+basic.toString = function (n, b) {
+	if (! basic.validate_base(b)) {
+	  throw new Error ("invalid base")
+	}
+	var s = ""
+	var dividend, residual
+	while (n) {
+	  remainder = mod(n, b)
+    n = Math.floor(n/b)
+		if (remainder) {
+		  n += 1
+		}
+		s += basic.abedecary[n]
+	}
+	return s
+}
+
+function mod(n,m){ return n-(m * Math.floor(n/m)) }
+