lambdas documentation

README.md

@@ -43,7 +43,7 @@ int main() {
 
 The output of this example will be:
 
-```
+```html
 Hi Chris!
 Hi Mark!
 Hi Scott!
@@ -66,7 +66,7 @@ a JSON object.
 
 Note that when using a `std::string` as value you must explicitly specify the 
 type, since a `const char*` literal like `"foobar"` would be implicitly 
-converted to bool. Alternatively you can use [C++14 string_literals](http://en.cppreference.com/w/cpp/string/basic_string/operator%22%22s)
+converted to `bool`. Alternatively you can use [C++14 string_literals](http://en.cppreference.com/w/cpp/string/basic_string/operator%22%22s)
 if your compiler supports it.
 
 ## Advanced usage
@@ -92,7 +92,7 @@ std::cout << mstch::render(view, context, {{"user", user_view}}) << std::endl;
 
 The output will be:
 
-```
+```html
 <strong>Chris</strong>
 <strong>Mark</strong>
 <strong>Scott</strong>
@@ -100,7 +100,51 @@ The output will be:
 
 ### Lambdas
 
-TODO
+C++11 lambda expressions can be used to add logic to your templates. Like a
+`const char*` literal, lambdas can be implicitly converted to `bool`, so they
+must be wrapped in a `mstch::lambda` object when used in a `mstch::node`.
+
+The lambda expression passed to `mstch::lambda` returns a `std::string` and 
+accepts either no parameters:
+
+```c++
+std::string view{"Hello {{lambda}}!"};
+mstch::map context{
+  {"lambda", mstch::lambda{[]() {
+    return std::string{"World"};
+  }}}
+};
+
+std::cout << mstch::render(view, context) << std::endl;
+```
+
+The output will be:
+
+```html
+Hello World!
+```
+
+Or it accepts a `const std::string&` and a `mstch::renderer`. The first one is 
+passed the unrendered literal block, the second is a `std::function` that can be 
+called to render it:
+
+```c++
+std::string view{"{{#bold}}{{yay}} :){{/bold}}"};
+mstch::map context{
+  {"yay", std::string{"Yay!"}},
+  {"bold", mstch::lambda{[](const std::string& text, mstch::renderer render) {
+    return "<b>" + render(text) + "</b>";
+  }}}
+};
+
+std::cout << mstch::render(view, context) << std::endl;
+```
+
+The output will be:
+
+```html
+<b>Yay! :)</b>
+```
 
 ### Objects