Initial commit

spell.h

@@ -0,0 +1,56 @@
+#include <string>
+#include <iostream>
+using std::string;
+
+const char* smallNumbers[] = {
+  "zero", "one", "two", "three", "four", "five",
+  "six", "seven", "eight", "nine", "ten",
+  "eleven", "twelve", "thirteen", "fourteen", "fifteen",
+  "sixteen", "seventeen", "eighteen", "nineteen"
+};
+
+string spellHundreds(unsigned n) {
+  string res;
+  if (n > 99) {
+    res = smallNumbers[n/100];
+    res += " hundred";
+    n %= 100;
+    if (n) res += " and ";
+  }
+  if (n >= 20) {
+    static const char* Decades[] = {
+      "", "", "twenty", "thirty", "forty",
+      "fifty", "sixty", "seventy", "eighty", "ninety"
+    };
+    res += Decades[n/10];
+    n %= 10;
+    if (n) res += "-";
+  }
+  if (n < 20 && n > 0)
+    res += smallNumbers[n];
+  return res;
+}
+
+const char* thousandPowers[] = {
+  " billion", " million",  " thousand", "" };
+
+typedef unsigned long Spellable;
+
+string spell(Spellable n) {
+  if (n < 20) return smallNumbers[n];
+  string res;
+  const char** pScaleName = thousandPowers;
+  Spellable scaleFactor = 1000000000;// 1 billion
+  while (scaleFactor > 0) {
+    if (n >= scaleFactor) {
+      Spellable h = n / scaleFactor;
+      res += spellHundreds(h) + *pScaleName;
+      n %= scaleFactor;
+      if (n) res += " ";
+    }
+    scaleFactor /= 1000;
+    ++pScaleName;
+  }
+  return res;
+}
+