Refactored formatters

Combined toI, toS and regexp method into a single object so
that mistakes a more obv since related methods
are closer together. This also enabled
us to extract more complex formatters into single files which might be
neccessary for mod_value_to_item_class

src/localize/formatters/Formatter.ts

@@ -0,0 +1,19 @@
+/**
+ * formats a given numberic value to string
+ */
+export default interface Formatter {
+  /**
+   * 
+   * @param n 
+   */
+  format(n: number): string;
+  /**
+   * inverse of #format
+   * @param s returnval from #format()
+   */
+  inverse(s: string): number;
+  /**
+   * RegExp to match the value in the formatted string
+   */
+  regexp: string;
+}

src/localize/__tests__/formatters.ts → src/localize/formatters/__tests__/formatters.ts

@@ -2,7 +2,7 @@ import factory, {
   formatters,
   inverseFactory,
   regexpFactory
-} from '../formatters';
+} from '../';
 
 it('should throw if the specified formatter doesnt exist', () => {
   expect(() => factory('foobar')).toThrowError("'foobar' not found");

src/localize/formatters/__tests__/regexp_util.ts

@@ -0,0 +1,11 @@
+import {NUMBER} from '../regexp_util';
+
+it('can match hole numbers', () => {
+  const regexp =  new RegExp(`^${NUMBER}$`);
+  expect(regexp.test(`${5}`)).toBe(true);
+  expect(regexp.test(`${-123}`)).toBe(true);
+  expect(regexp.test(`${-0}`)).toBe(true);
+  expect(regexp.test(`${+0}`)).toBe(true);
+  expect(regexp.test(`${-9.5}`)).toBe(false);
+  expect(regexp.test(`${13.5}`)).toBe(false);
+})