# doctemplates

This is the templating system used by pandoc.  It was formerly

be a module in pandoc. It has been split off to make it easier

to use independently.

Example:

``` haskell

{-# LANGUAGE OverloadedStrings #-}

import Data.Text

import Data.Aeson

import Text.DocTemplates

data Employee = Employee { firstName :: String

                         , lastName  :: String

                         , salary    :: Maybe Int }

instance ToJSON Employee where

  toJSON e = object [ "name" .= object [ "first" .= firstName e

                                       , "last"  .= lastName e ]

                    , "salary" .= salary e ]

template :: Text

template = "$for(employee)$Hi, $employee.name.first$. $if(employee.salary)$You make $employee.salary$.$else$No salary data.$endif$$sep$\n$endfor$"

main = case compileTemplate template of

         Left e    -> error e

         Right t   -> putStrLn $ renderTemplate t $ object

                        ["employee" .=

                          [ Employee "John" "Doe" Nothing

                          , Employee "Omar" "Smith" (Just 30000)

                          , Employee "Sara" "Chen" (Just 60000) ]

                        ]

```

A slot for an interpolated variable is a variable name surrounded

by dollar signs.  To include a literal `$` in your template, use

`$$`.  Variable names must begin with a letter and can contain letters,

numbers, `_`, `-`, and `.`.

The values of variables are determined by a JSON object that is

passed as a parameter to `renderTemplate`.  So, for example,

`title` will return the value of the `title` field, and

`employee.salary` will return the value of the `salary` field

of the object that is the value of the `employee` field.

The value of a variable will be indented to the same level as the

variable.

A conditional begins with `$if(variable_name)$` and ends with `$endif$`.

It may optionally contain an `$else$` section.  The if section is

used if `variable_name` has a non-null value, otherwise the else section

is used.

Conditional keywords should not be indented, or unexpected spacing

problems may occur.

The `$for$` keyword can be used to iterate over an array.  If

the value of the associated variable is not an array, a single

iteration will be performed on its value.

You may optionally specify separators using `$sep$`, as in the

example above.

Anything between the sequence `$--` and the end of the line

will be treated as a comment.