Added _.partialRight

6 files changed, 151 insertions, 8 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 359df92..e28af67 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 * Added `_.toObj`
 * Added `_.noop`
+* Added `_.partialRight`
 
 ## 1.5.1 (04/13/17)
 
diff --git a/doc/index.html b/doc/index.html
index 27bbb34..6ef18b5 100644
--- a/doc/index.html
+++ b/doc/index.html
@@ -455,6 +455,10 @@
 	<td class="summary">Partially apply a function by filling in any number of its arguments.</td>
 	</tr>
 	<tr>
+	<td class="name" nowrap><a href="#partialRight">partialRight (f, ...)</a></td>
+	<td class="summary">Similar to <a href="index.html#partial">partial</a>, but from the right.</td>
+	</tr>
+	<tr>
 	<td class="name" nowrap><a href="#curry">curry (f[, n_args])</a></td>
 	<td class="summary">Curries a function.</td>
 	</tr>
@@ -3762,13 +3766,47 @@
     <h3>Returns:</h3>
     <ol>
 
-        a new version of function f where having some of it original arguments filled
+        a new version of function f having some of it original arguments filled
+    </ol>
+
+
+    <h3>See also:</h3>
+    <ul>
+         <li><a href="index.html#partialRight">partialRight</a></li>
+         <li><a href="index.html#curry">curry</a></li>
+    </ul>
+
+
+</dd>
+    <dt>
+    <a name = "partialRight"></a>
+    <strong>partialRight (f, ...)</strong>
+    </dt>
+    <dd>
+    Similar to <a href="index.html#partial">partial</a>, but from the right.
+
+
+    <h3>Parameters:</h3>
+    <ul>
+        <li><span class="parameter">f</span>
+         a function
+        </li>
+        <li><span class="parameter">...</span>
+         a list of partial arguments to <code>f</code>
+        </li>
+    </ul>
+
+    <h3>Returns:</h3>
+    <ol>
+
+        a new version of function f having some of it original arguments filled
     </ol>
 
 
     <h3>See also:</h3>
     <ul>
-         <a href="index.html#curry">curry</a>
+         <li><a href="index.html#partialRight">partialRight</a></li>
+         <li><a href="index.html#curry">curry</a></li>
     </ul>
 
 
@@ -3803,7 +3841,8 @@
 
     <h3>See also:</h3>
     <ul>
-         <a href="index.html#partial">partial</a>
+         <li><a href="index.html#partial">partial</a></li>
+         <li><a href="index.html#partialRight">partialRight</a></li>
     </ul>
 
 
@@ -4732,7 +4771,7 @@
 </div> <!-- id="main" -->
 <div id="about">
 <i>generated by <a href="http://github.com/stevedonovan/LDoc">LDoc 1.4.6</a></i>
-<i style="float:right;">Last updated 2017-04-14 08:14:37 </i>
+<i style="float:right;">Last updated 2017-04-14 09:04:58 </i>
 </div> <!-- id="about" -->
 </div> <!-- id="container" -->
 </body>
diff --git a/doc/topics/tutorial.md.html b/doc/topics/tutorial.md.html
index 87bc9ca..e3d07ff 100644
--- a/doc/topics/tutorial.md.html
+++ b/doc/topics/tutorial.md.html
@@ -1665,7 +1665,7 @@ iter_po2() <span class="comment">-- =&gt; 2
 </pre>
 
 
-<p>The string <code>&apos;_&apos;</code> can be used as a placeholder in the list of arguments to specify an argument that should not be pre-filled, but left open to be supplied at call-time.</p>
+<p>The string <code>&apos;_&apos;</code> can be used as a placeholder in the list of arguments to specify an argument that should not be pre-filled, but is rather left open to be supplied at call-time.</p>
 
 <pre>
 <span class="keyword">local</span> <span class="keyword">function</span> diff(a, b) <span class="keyword">return</span> a - b <span class="keyword">end</span>
@@ -1674,6 +1674,39 @@ iter_po2() <span class="comment">-- =&gt; 2
 </pre>
 
 
+<h3>partialRight (f, &hellip;)</h3>
+
+<p>Like <code>_.partial</code>, it partially applies a function by filling in any number of its arguments, but from the right.</p>
+
+<pre>
+<span class="keyword">local</span> <span class="keyword">function</span> concat(...) <span class="keyword">return</span> <span class="global">table</span>.concat({...},<span class="string">','</span>) <span class="keyword">end</span>
+<span class="keyword">local</span> concat_right = _.partialRight(concat,<span class="string">'a'</span>,<span class="string">'b'</span>,<span class="string">'c'</span>)
+concat_right(<span class="string">'d'</span>) <span class="comment">-- =&gt; d,a,b,c
+</span>
+concat_right = _.partialRight(concat,<span class="string">'a'</span>,<span class="string">'b'</span>)
+concat_right(<span class="string">'c'</span>,<span class="string">'d'</span>) <span class="comment">-- =&gt; c,d,a,b
+</span>
+concat_right = _.partialRight(concat,<span class="string">'a'</span>)
+concat_right(<span class="string">'b'</span>,<span class="string">'c'</span>,<span class="string">'d'</span>) <span class="comment">-- =&gt; b,c,d,a</span>
+</pre>
+
+
+<p>The string <code>&apos;_&apos;</code>, as always, can be used as a placeholder in the list of arguments to specify an argument that should not be pre-filled, but is rather left open to be supplied at call-time.
+In that case, the first args supplied at runtime will be used to fill the initial list of args while the remaining will be prepended.</p>
+
+<pre>
+<span class="keyword">local</span> <span class="keyword">function</span> concat(...) <span class="keyword">return</span> <span class="global">table</span>.concat({...},<span class="string">','</span>) <span class="keyword">end</span>
+<span class="keyword">local</span> concat_right = _.partialRight(concat,<span class="string">'a'</span>,<span class="string">'_'</span>,<span class="string">'c'</span>)
+concat_right(<span class="string">'d'</span>,<span class="string">'b'</span>) <span class="comment">-- =&gt; b,a,d,c
+</span>
+concat_right = _.partialRight(concat,<span class="string">'a'</span>,<span class="string">'b'</span>,<span class="string">'_'</span>)
+concat_right(<span class="string">'c'</span>,<span class="string">'d'</span>) <span class="comment">-- =&gt; d,a,b,c
+</span>
+concat_right = _.partialRight(concat,<span class="string">'_'</span>,<span class="string">'a'</span>)
+concat_right(<span class="string">'b'</span>,<span class="string">'c'</span>,<span class="string">'d'</span>) <span class="comment">-- =&gt; c,d,b,a</span>
+</pre>
+
+
 <h3>curry (f, n_args)</h3>
 
 <p>Curries a function. If the given function <code>f</code> takes multiple arguments, it returns another version of <code>f</code> that takes a single argument
@@ -2154,7 +2187,7 @@ _.import(context, <span class="keyword">true</span>)
 </div> <!-- id="main" -->
 <div id="about">
 <i>generated by <a href="http://github.com/stevedonovan/LDoc">LDoc 1.4.6</a></i>
-<i style="float:right;">Last updated 2017-04-14 08:14:37 </i>
+<i style="float:right;">Last updated 2017-04-14 09:04:58 </i>
 </div> <!-- id="about" -->
 </div> <!-- id="container" -->
 </body>
diff --git a/doc/tutorial.md b/doc/tutorial.md
index cfb6c46..31906a2 100644
--- a/doc/tutorial.md
+++ b/doc/tutorial.md
@@ -1436,7 +1436,7 @@ local diffFrom20 = _.partial(diff, 20) -- arg 'a' will be 20 by default
 diffFrom20(5) -- => 15
 ````
 
-The string `'_'` can be used as a placeholder in the list of arguments to specify an argument that should not be pre-filled, but left open to be supplied at call-time.
+The string `'_'` can be used as a placeholder in the list of arguments to specify an argument that should not be pre-filled, but is rather left open to be supplied at call-time.
 
 ```lua
 local function diff(a, b) return a - b end
@@ -1444,6 +1444,37 @@ local remove5 = _.partial(diff, '_', 5) -- arg 'a' will be given at call-time, b
 remove5(20) -- => 15
 ````
 
+### partialRight (f, ...)
+
+Like `_.partial`, it partially applies a function by filling in any number of its arguments, but from the right.
+
+```lua
+local function concat(...) return table.concat({...},',') end
+local concat_right = _.partialRight(concat,'a','b','c')
+concat_right('d') -- => d,a,b,c
+
+concat_right = _.partialRight(concat,'a','b')
+concat_right('c','d') -- => c,d,a,b
+
+concat_right = _.partialRight(concat,'a')
+concat_right('b','c','d') -- => b,c,d,a
+```
+
+The string `'_'`, as always, can be used as a placeholder in the list of arguments to specify an argument that should not be pre-filled, but is rather left open to be supplied at call-time.
+In that case, the first args supplied at runtime will be used to fill the initial list of args while the remaining will be prepended.
+
+```lua
+local function concat(...) return table.concat({...},',') end
+local concat_right = _.partialRight(concat,'a','_','c')
+concat_right('d','b') -- => b,a,d,c
+
+concat_right = _.partialRight(concat,'a','b','_')
+concat_right('c','d') -- => d,a,b,c
+
+concat_right = _.partialRight(concat,'_','a')
+concat_right('b','c','d') -- => c,d,b,a
+````
+
 ### curry (f, n_args)
 
 Curries a function. If the given function `f` takes multiple arguments, it returns another version of `f` that takes a single argument 
diff --git a/moses.lua b/moses.lua
index e56d370..1432f2b 100644
--- a/moses.lua
+++ b/moses.lua
@@ -1516,7 +1516,8 @@ end
 -- @name partial
 -- @param f a function
 -- @param ... a list of partial arguments to `f`
--- @return a new version of function f where having some of it original arguments filled
+-- @return a new version of function f having some of it original arguments filled
+-- @see partialRight
 -- @see curry
 function _.partial(f,...)
 	local partial_args = {...}
@@ -1530,6 +1531,25 @@ function _.partial(f,...)
 	end
 end
 
+--- Similar to @{partial}, but from the right.
+-- @name partialRight
+-- @param f a function
+-- @param ... a list of partial arguments to `f`
+-- @return a new version of function f having some of it original arguments filled
+-- @see partialRight
+-- @see curry
+function _.partialRight(f,...)
+	local partial_args = {...}
+	return function (...)
+		local n_args = {...}	
+		local f_args = {}
+		for k = 1,#partial_args do
+			f_args[k] = (partial_args[k] == '_') and _.pop(n_args) or partial_args[k]
+		end
+		return f(unpack(_.append(n_args, f_args)))
+	end
+end
+
 --- Curries a function. If the given function `f` takes multiple arguments, it returns another version of 
 -- `f` that takes a single argument (the first of the arguments to the original function) and returns a new 
 -- function that takes the remainder of the arguments and returns the result. 
@@ -1538,6 +1558,7 @@ end
 -- @param[opt] n_args the number of arguments expected for `f`. Defaults to 2.
 -- @return a curried version of `f`
 -- @see partial
+-- @see partialRight
 function _.curry(f, n_args)
 	n_args = n_args or 2
 	local _args = {}
diff --git a/spec/func_spec.lua b/spec/func_spec.lua
index a46763c..0d3ea97 100644
--- a/spec/func_spec.lua
+++ b/spec/func_spec.lua
@@ -337,6 +337,24 @@ context('Utility functions specs', function()
 		
 	end)
 	
+	context('partialRight', function()
+
+		test('applies partial but from the right',function()
+			local function concat(a,b,c,d) return a..b..c..d end
+			assert_equal(_.partialRight(concat,'a','b','c')('d'), 'dabc')
+			assert_equal(_.partialRight(concat,'a','b')('c','d'), 'cdab')
+			assert_equal(_.partialRight(concat,'a')('b','c','d'), 'bcda')
+		end)
+		
+		test('\'_\' can be used as a placeholder',function()
+			local function concat(a,b,c,d) return a..b..c..d end		
+			assert_equal(_.partialRight(concat,'a','_','c')('d','b'), 'badc')
+			assert_equal(_.partialRight(concat,'a','b','_')('c','d'), 'dabc')
+			assert_equal(_.partialRight(concat,'_','a')('b','c','d'), 'cdba')
+		end)
+		
+	end)	
+	
 	context('curry', function()
 
 		test('curries a function for a specific number of args',function()