Template functions

Template functions:

implement control flow and conditionals, for example if() and switch()
render widgets and snippets of HTML, for example std:ui:notice() and std:form:token()
include other templates in the current template.

There are three categories of template functions provided by the platform:

language functions, which implement core features of the HSVT language
ui functions, which affect the rendering of the standard Haplo UI
platform functions, which provide rendering of widgets

Plugins can define their own template functions. These are made available to all plugins, so must be in an appropriate namespace.

Function syntax

A function is formed of

the function name
an open bracket (
zero or more arguments, separated by spaces (not commas)
a close bracket )
an optional anonymous block
zero or more named blocks

A block is a number of other language elements enclosed in {} brackets, and a named block is prefixed by a name.

For example, the usual if() function looks like

if(value) {
    "True"
} else {
    "False"
}

and is formed of the name, a single argument in () brackets, an anonymous block containing the literal "True" and a named else block containing the literal "False".

But of course, functions can be as simple as this

<form method="POST"> std:form:token()
    // ...
</form>

where std:form:token() includes the standard CSRF token into your view.