provide a placeholder value

README.md

@@ -86,19 +86,16 @@ inc(7);
 One may wish to partially apply a function whose parameters are in the "wrong"
 order. All functions defined via sanctuary-def accommodate this by accepting
 "placeholders". A placeholder is an object with a `'@@functional/placeholder'`
-property whose value is `true`. [`R.__`][1] is one such object. A placeholder
+property whose value is `true`. `$.__` is one such object. A placeholder
 indicates an argument yet to be provided. For example:
 
 ```javascript
-//    _ :: Placeholder
-const _ = {'@@functional/placeholder': true};
-
 //    concatS :: String -> String -> String
 const concatS =
 def('concatS', {}, [$.String, $.String, $.String], (x, y) => x + y);
 
 //    exclaim :: String -> String
-const exclaim = concatS(_, '!');
+const exclaim = concatS($.__, '!');
 
 exclaim('ahoy');
 // => 'ahoy!'
@@ -179,7 +176,7 @@ Type comprising every Function value.
 $.Arguments :: Type
 ```
 
-Type comprising every [`arguments`][2] object.
+Type comprising every [`arguments`][1] object.
 
 #### `Array`
 
@@ -212,7 +209,7 @@ $.Error :: Type
 ```
 
 Type comprising every Error value, including values of more specific
-constructors such as [`SyntaxError`][3] and [`TypeError`][4].
+constructors such as [`SyntaxError`][2] and [`TypeError`][3].
 
 #### `FiniteNumber`
 
@@ -243,7 +240,7 @@ $.Integer :: Type
 ```
 
 Type comprising every integer in the range
-[[`Number.MIN_SAFE_INTEGER`][5] .. [`Number.MAX_SAFE_INTEGER`][6]].
+[[`Number.MIN_SAFE_INTEGER`][4] .. [`Number.MAX_SAFE_INTEGER`][5]].
 
 #### `NegativeFiniteNumber`
 
@@ -328,7 +325,7 @@ $.Object :: Type
 Type comprising every "plain" Object value. Specifically, values created via:
 
   - object literal syntax;
-  - [`Object.create`][7]; or
+  - [`Object.create`][6]; or
   - the `new` operator in conjunction with `Object` or a custom
     constructor function.
 
@@ -731,11 +728,11 @@ showCard(Pair('X', '♠'));
 
 #### `EnumType`
 
-`EnumType` is used to construct [enumerated types][8].
+`EnumType` is used to construct [enumerated types][7].
 
 To define an enumerated type one must provide:
 
-  - an array of values with distinct [`R.toString`][9] representations.
+  - an array of values with distinct [`R.toString`][8] representations.
 
 ```haskell
 EnumType :: Array Any -> Type
@@ -973,8 +970,8 @@ _concat([1, 2], 'buzz');
 
 The type of `_concat` is misleading: it suggests that it can operate on any
 two values of *any* one type. In fact there's an implicit constraint, since
-the type must support concatenation (in [mathematical][10] terms, the type
-must have a [semigroup][11]). The run-time type errors that result when this
+the type must support concatenation (in [mathematical][9] terms, the type
+must have a [semigroup][10]). The run-time type errors that result when this
 constraint is violated are not particularly descriptive:
 
 ```javascript
@@ -1029,14 +1026,13 @@ Multiple constraints may be placed on a type variable by including multiple
 `TypeClass` values in the list (e.g. `{a: [Foo, Bar, Baz]}`).
 
 
-[1]: http://ramdajs.com/docs/#__
-[2]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/arguments
-[3]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SyntaxError
-[4]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError
-[5]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MIN_SAFE_INTEGER
-[6]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER
-[7]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create
-[8]: https://en.wikipedia.org/wiki/Enumerated_type
-[9]: http://ramdajs.com/docs/#toString
-[10]: https://en.wikipedia.org/wiki/Semigroup
-[11]: https://github.com/fantasyland/fantasy-land#semigroup
+[1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/arguments
+[2]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SyntaxError
+[3]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError
+[4]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MIN_SAFE_INTEGER
+[5]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER
+[6]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create
+[7]: https://en.wikipedia.org/wiki/Enumerated_type
+[8]: http://ramdajs.com/docs/#toString
+[9]: https://en.wikipedia.org/wiki/Semigroup
+[10]: https://github.com/fantasyland/fantasy-land#semigroup

index.js

@@ -15,7 +15,7 @@
 
   'use strict';
 
-  var $ = {};
+  var $ = {__: {'@@functional/placeholder': true}};
 
   var MAX_SAFE_INTEGER = Math.pow(2, 53) - 1;
   var MIN_SAFE_INTEGER = -MAX_SAFE_INTEGER;

test/index.js

@@ -348,9 +348,9 @@ describe('def', function() {
     var triple =
     def('triple', {}, [$.Number, $.Number, $.Number, $.Array($.Number)], list);
 
-    eq(triple(R.__, R.__, 3)(R.__, 2)(1), [1, 2, 3]);
+    eq(triple($.__, $.__, 3)($.__, 2)(1), [1, 2, 3]);
 
-    throws(function() { triple(R.__, /x/); },
+    throws(function() { triple($.__, /x/); },
            errorEq(TypeError,
                    'Invalid value\n' +
                    '\n' +
@@ -362,7 +362,7 @@ describe('def', function() {
                    '\n' +
                    'The value at position 1 is not a member of ‘Number’.\n'));
 
-    throws(function() { triple(R.__, R.__, /x/); },
+    throws(function() { triple($.__, $.__, /x/); },
            errorEq(TypeError,
                    'Invalid value\n' +
                    '\n' +
@@ -374,7 +374,7 @@ describe('def', function() {
                    '\n' +
                    'The value at position 1 is not a member of ‘Number’.\n'));
 
-    throws(function() { triple(R.__, 2, 3)(/x/); },
+    throws(function() { triple($.__, 2, 3)(/x/); },
            errorEq(TypeError,
                    'Invalid value\n' +
                    '\n' +
@@ -584,14 +584,14 @@ describe('def', function() {
     var a000 = def('a00', {}, [a, a, a, $.Array(a)], Array);
     var anum = a000(1);
     var astr = a000('a');
-    var bstr = a000(R.__, 'b');
+    var bstr = a000($.__, 'b');
     var abstr = astr('b');
 
     eq(anum(2, 3), [1, 2, 3]);
     eq(anum(2)(3), [1, 2, 3]);
     eq(astr('b', 'c'), ['a', 'b', 'c']);
     eq(bstr('a', 'c'), ['a', 'b', 'c']);
-    eq(astr(R.__, 'c')('b'), ['a', 'b', 'c']);
+    eq(astr($.__, 'c')('b'), ['a', 'b', 'c']);
     eq(abstr('c'), ['a', 'b', 'c']);
   });
 
@@ -1432,7 +1432,7 @@ describe('def', function() {
     def('values',
         {},
         [$.StrMap(a), $.Array(a)],
-        function(m) { return R.map(R.prop(R.__, m), keys(m)); });
+        function(m) { return R.map(R.prop($.__, m), keys(m)); });
 
     var o = Object.create(null);
     o.x = 1;
@@ -1622,7 +1622,7 @@ describe('def', function() {
                    '\n' +
                    'Since there is no type of which all the above values are members, the type-variable constraint has been violated.\n'));
 
-    throws(function() { aa(R.__, 0)(/x/); },
+    throws(function() { aa($.__, 0)(/x/); },
            errorEq(TypeError,
                    'Type-variable constraint violation\n' +
                    '\n' +
@@ -2254,7 +2254,7 @@ describe('def', function() {
                    '\n' +
                    '‘or’ requires ‘a’ to satisfy the Alternative type-class constraint; the value at position 1 does not.\n'));
 
-    throws(function() { or(R.__, Right(1)); },
+    throws(function() { or($.__, Right(1)); },
            errorEq(TypeError,
                    'Type-class constraint violation\n' +
                    '\n' +
@@ -2290,7 +2290,7 @@ describe('def', function() {
                    '\n' +
                    '‘concat’ requires ‘a’ to satisfy the Semigroup type-class constraint; the value at position 1 does not.\n'));
 
-    throws(function() { concat(R.__, /x/); },
+    throws(function() { concat($.__, /x/); },
            errorEq(TypeError,
                    'Type-class constraint violation\n' +
                    '\n' +