Template Syntax


A Lambda represents a way of defining a simple method model. A lambda is an expression, and can appear anywhere an expression can appear.

Most simply, a lambda can be used to create a method as follows:

<assign increment = #lambda(x) x + 1>

<p>Next value is: ${increment(10)}</p>

Lambdas can also be used to create and pass anonymous methods into other method calls, as follows:

<assign list = [ 1, 2, 3, 4 ,5 ]>
<assign sum = methods.reduce( list, #lambda(x, y) x + y )>

<p>Sum is: ${sum}.</p>

Lambdas can be used to create closures. A closure can reference template model variables from the scope in which the lambda was created. For example:

<assign list = [ "one", "two", "three", "four" ,"five" ]>
<assign filtered = methods.filter( list, #lambda(x) methods.match( "m/o/", x ))>

In the example above, the lambda refers to the methods.match method from the scope in which the lambda was created.

Lambdas are typically used in conjunction with a functional programming style. The filter, map, and reduce methods of the freemarker.ext.misc package are common examples of functional programming style. These methods are commonly called high-order functions. See the JavaDoc for more details of these methods.