Merge pull request documentcloud#163 from jacobpurcell/conjoin-disjoin-single-elem

Support conjoin and disjoin methods for single elements

Author: fogus

test/function.combinators.js

@@ -18,13 +18,17 @@ $(document).ready(function() {
   test("conjoin", function() {
     var isPositiveEven = _.conjoin(function(x) { return x > 0; }, function(x) { return (x & 1) === 0; });
 
+    equal(isPositiveEven(2), true, 'should recognize that element satisfies a conjunction');
+    equal(isPositiveEven(1), false, 'should recognize that element does not satisfy a conjunction');
     equal(isPositiveEven([2,4,6,8]), true, 'should recognize when all elements satisfy a conjunction');
     equal(isPositiveEven([2,4,6,7,8]), false, 'should recognize when an element fails to satisfy a conjunction');
   });
 
   test("disjoin", function() {
     var orPositiveEven = _.disjoin(function(x) { return x > 0; }, function(x) { return (x & 1) === 0; });
 
+    equal(orPositiveEven(2), true, 'should recognize that element satisfies a disjunction');
+    equal(orPositiveEven(-1), false, 'should recognize that element does not satisfy a disjunction');
     equal(orPositiveEven([-1,2,3,4,5,6]), true, 'should recognize when all elements satisfy a disjunction');
     equal(orPositiveEven([-1,-3]), false, 'should recognize when an element fails to satisfy a disjunction');
   });

underscore.function.combinators.js

@@ -31,7 +31,22 @@
     };
   };
 
+  var createPredicateApplicator = function (funcToInvoke /*, preds */) {
+    var preds = _(arguments).tail();
+
+    return function (objToCheck) {
+      var array = _(objToCheck).cat();
+
+      return _[funcToInvoke](array, function (e) {
+        return _[funcToInvoke](preds, function (p) {
+          return p(e);
+        });
+      });
+    };
+  };
+
   // n.b. depends on underscore.function.arity.js
+  // n.b. depends on underscore.array.builders.js
 
   // Takes a target function and a mapping function. Returns a function
   // that applies the mapper to its arguments before evaluating the body.
@@ -64,32 +79,12 @@
     // Composes a bunch of predicates into a single predicate that
     // checks all elements of an array for conformance to all of the
     // original predicates.
-    conjoin: function(/* preds */) {
-      var preds = arguments;
-
-      return function(array) {
-        return _.every(array, function(e) {
-          return _.every(preds, function(p) {
-            return p(e);
-          });
-        });
-      };
-    },
+    conjoin: _.partial(createPredicateApplicator, ('every')),
 
     // Composes a bunch of predicates into a single predicate that
     // checks all elements of an array for conformance to any of the
     // original predicates.
-    disjoin: function(/* preds */) {
-      var preds = arguments;
-
-      return function(array) {
-        return _.some(array, function(e) {
-          return _.some(preds, function(p) {
-            return p(e);
-          });
-        });
-      };
-    },
+    disjoin: _.partial(createPredicateApplicator, 'some'),
 
     // Takes a predicate-like and returns a comparator (-1,0,1).
     comparator: function(fun) {