Add "node_modules" to .gitignore. Clarify how head() works. Add pop() method.

.gitignore

@@ -1 +1,2 @@
 *.swp
+node_modules/

lazy.js

@@ -74,12 +74,13 @@ function Lazy (em, opts) {
         );
     }
 
+    self.pop = function (f) {
+        self.head(f);
+        return self.skip(1);
+    }
+
     self.head = function (f) {
-        var lazy = newLazy();
-        lazy.on(dataName, function g (x) {
-            f(x)
-            lazy.removeListener(dataName, g)
-        })
+        self.once(dataName, f);
     }
 
     self.tail = function () {

readme.txt

@@ -153,6 +153,7 @@ Supports the following operations:
     * lazy.product(f)
     * lazy.foldr(op, i, f)
     * lazy.skip(n)
+    * lazy.pop(f)
     * lazy.head(f)
     * lazy.tail(f)
     * lazy.join(f)

test/head.js

@@ -2,25 +2,33 @@ var assert = require('assert');
 var Lazy = require('..');
 var expresso = expresso;
 
-function range(i, j) {
-    var r = [];
-    for (;i<j;i++) r.push(i);
-    return r;
-}
-
 exports['head'] = function () {
     var lazy = new Lazy;
-    var data = [];
     var executed = 0;
-    lazy.head(function (x) {
-        assert.equal(x, 0);
-        executed++;
-    })
+    var expect = function(n) {
+        return function(x) {
+            executed++;
+            assert.eql(x, n);
+        }
+    }
 
-    range(0,10).forEach(function (x) {
+    // callback should only execute once.
+    lazy.head(expect(12));
+    [12, 13, 14].forEach(function (x) {
         lazy.emit('data', x);
     });
+    assert.equal(executed, 1);
 
-    assert.equal(executed, 1, 'head executed too much');
+    // multiple calls to head leave the lazy list unchanged.
+    lazy.head(expect(123));
+    lazy.head(expect(123));
+    lazy.head(expect(123));
+    lazy.join(expect([123, 456, 789]));
+    [123, 456, 789].forEach(function(x) {
+        lazy.emit('data', x);
+    })
+    assert.equal(executed, 4);
+    lazy.emit('end');
+    assert.equal(executed, 5);
 }
 

test/pop.js

@@ -0,0 +1,27 @@
+var assert = require('assert');
+var Lazy = require('..');
+var expresso = expresso;
+
+exports['pop'] = function () {
+    var lazy = new Lazy;
+    var executed = 0;
+
+    var expect = function(n) {
+        return function(x) {
+            executed++;
+            assert.eql(x, n);
+        }
+    }
+
+    lazy.pop(expect(77))
+        .pop(expect(99))
+        .join(expect([11, 55, 33]));
+
+    [77, 99, 11, 55, 33].forEach(function (x) {
+        lazy.emit('data', x);
+    });
+    lazy.emit('end');
+
+    assert.equal(executed, 3);
+}
+