re-write using Underscore.js

coffeescript/euler.coffee

@@ -0,0 +1,39 @@
+_ = require './underscore.js'
+
+exports.factors = (x) ->
+  output = []
+  root = Math.sqrt x
+  for y in [0...root]
+    if x % y == 0
+      output.push y
+      output.push x / y
+  if x % root == 0 then output.push root
+  output
+
+exports.fibs = (max) ->
+  if max == 0 then return [0]
+  output = [0, 1]
+  while (x = output[output.length - 1] + output[output.length - 2]) <= max
+    output.push x
+  output
+
+exports.gcd = (x, y) ->
+  if y == 0 then x
+  else exports.gcd y, x % y
+
+exports.isPalindrome = (x) ->
+  s = x.toString()
+  for i in [0...s.length / 2]
+    if s[i] != s[s.length - 1 - i]
+      return false
+  true
+
+exports.isPrime = (x) ->
+  (exports.factors x).length == 2
+
+exports.lcm = (x, y) ->
+  (Math.abs (x * y)) / (exports.gcd x, y)
+
+exports.sum = (xs) ->
+  add = (x, y) -> x + y
+  _.reduce xs, add, 0

coffeescript/p1.coffee

@@ -1,6 +1,4 @@
-sum = (xs...) ->
-  output = 0
-  output += x for x in xs
-  output
+euler = require './euler.coffee'
+_ = require './underscore.js'
 
-alert sum (x for x in [0...1000] when x % 3 == 0 or x % 5 == 0)...
+console.log euler.sum _.select [0...1000], (x) -> x % 3 == 0 or x % 5 == 0

coffeescript/p2.coffee

@@ -1,14 +1,4 @@
-sum = (xs...) ->
-  output = 0
-  output += x for x in xs
-  output
+euler = require './euler.coffee'
+_ = require './underscore.js'
 
-fibs = (max) ->
-  if max < 0 then return []
-  if max == 0 then return [0]
-  output = [0, 1]
-  while (n = output[output.length - 2] + output[output.length - 1]) <= max
-    output.push n
-  output
-
-alert sum (x for x in fibs 4000000 when x % 2 == 0)...
+console.log euler.sum _.select (euler.fibs 4000000), (x) -> x % 2 == 0

coffeescript/p3.coffee

@@ -1,14 +1,4 @@
-factors = (x) ->
-  output = []
-  root = Math.sqrt x
-  for y in [0...root]
-    if x % y == 0
-      output.push y
-      output.push x / y
-  if x % root == 0 then output.push root
-  output
+euler = require './euler.coffee'
+_ = require './underscore.js'
 
-isPrime = (x) ->
-  2 == (factors x).length
-
-alert Math.max (x for x in factors 600851475143 when isPrime x)...
+console.log _.max _.select (euler.factors 600851475143), euler.isPrime

coffeescript/p4.coffee

@@ -1,9 +1,5 @@
-isPalindrome = (x) ->
-  s = x.toString()
-  for i in [0...s.length / 2]
-    if s[i] != s[s.length - 1 - i]
-      return false
-  return true
+euler = require './euler.coffee'
+_ = require './underscore.js'
 
 products = () ->
   output = []
@@ -12,4 +8,4 @@ products = () ->
       output.push (x * y)
   output
 
-alert Math.max (x for x in products() when isPalindrome x)...
+console.log _.max _.select products(), euler.isPalindrome

coffeescript/p5.coffee

@@ -1,14 +1,4 @@
-gcd = (x, y) ->
-  if y == 0 then x
-  else gcd y, x % y
+euler = require './euler.coffee'
+_ = require './underscore.js'
 
-lcm = (x, y) ->
-  (Math.abs (x * y)) / (gcd x, y)
-
-lcmAll = (x, y, zs...) ->
-  output = lcm x, y
-  for z in zs
-    output = lcm output, z
-  output
-
-alert lcmAll [1...21]...
+console.log _.reduce [1...21], euler.lcm, 1