feat(mapper): add convenience mapper method

javiercejudo · Feb 13, 2016 · 3f2818c · 3f2818c
1 parent 7d801c2
commit 3f2818c
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Showing 3 changed files with 27 additions and 13 deletions.
diff --git a/README.md b/README.md
@@ -35,24 +35,22 @@ fn.raw(d, 10, [2, 3/10]); // d(30)
 ## Use case: functional hex to dec
 
 ```js
-var R = require('ramda');
-var fn = require('positional-notation');
+const R = require('ramda');
+const fn = require('positional-notation');
 
-var symbols = {
+const symbols = {
   '0': '0', '1': '1', '2': '2', '3': '3', '4': '4', '5': '5', '6': '6', '7': '7', '8': '8', '9': '9',
   'A': '10', 'B': '11', 'C': '12', 'D': '13', 'E': '14', 'F': '15',
 };
 
-var posNotation = fn(Object.keys(symbols).length);
+const posNotation = fn(Object.keys(symbols).length);
 
-var hexToDec = R.pipe(
+const hexToDec = R.pipe(
   R.toUpper,
   R.split(''),
   R.reverse,
   R.map(R.prop(R.__, symbols)),
-  R.addIndex(R.map)(function(val, index) {
-    return posNotation([index, val]);
-  }),
+  R.addIndex(R.map)(fn.mapper(posNotation)),
   R.sum
 );
 

diff --git a/src/index.js b/src/index.js
@@ -13,13 +13,19 @@ var floatingAdapter = require('floating-adapter');
 
 var Decimal = pipe(times, pow)(coreArbitraryPrecision(floatingAdapter));
 var toDecimal = toDecimalFactory(Decimal);
+var curry3 = curryN(3);
 
-var positionalNotationRaw = curryN(3, function (d, base, posValPair) {
+var positionalNotationRaw = curry3(function (d, base, posValPair) {
   return d(base).pow(d(posValPair[0]))
     .times(d(posValPair[1]));
 });
 
 var positionalNotation = curryN(2, pipe(positionalNotationRaw(toDecimal), Number));
+
 positionalNotation.raw = positionalNotationRaw;
 
+positionalNotation.mapper = curry3(function(f, val, index) {
+  return f([index, val]);
+});
+
 module.exports = positionalNotation;
diff --git a/test/spec.js b/test/spec.js
@@ -49,7 +49,7 @@ describe('positional notation', function() {
   });
 });
 
-describe('use case', function() {
+describe('use case: functional hex to dec', function() {
   var symbols = {
     '0': '0', '1': '1', '2': '2', '3': '3', '4': '4', '5': '5', '6': '6', '7': '7', '8': '8', '9': '9',
     'A': '10', 'B': '11', 'C': '12', 'D': '13', 'E': '14', 'F': '15',
@@ -62,12 +62,22 @@ describe('use case', function() {
     R.split(''),
     R.reverse,
     R.map(R.prop(R.__, symbols)),
-    R.addIndex(R.map)(function(val, index) {
-      return posNotation([index, val]);
-    }),
+    R.addIndex(R.map)(fn.mapper(posNotation)),
     R.sum
   );
 
+  // Vanilla equivalent
+
+  // var hexToDec = function(hex) {
+  //   return hex
+  //     .toUpperCase()
+  //     .split('')
+  //     .reverse()
+  //     .map(function(val) { return symbols[val]; })
+  //     .map(fn.mapper(posNotation))
+  //     .reduce(function(acc, val) { return acc + val; }, 0);
+  // };
+
   it('hexadecimal to decimal', function() {
     hexToDec('AB').should.be.exactly(171);