Immersive includes a simple integrated text templating engine.
A template consists of regular text, with substitutions between {{/}}. In
addition to the regular control character escapes (\a, \b, \e, \f,
\n, \r, \t, \v), \{ can be escaped outside of substitution tags.
Inside a tag \} and \: must be escaped, as well as \[ depending on the
part of the tag it is in.
The most basic substitution tag is {{<variable name>}}. So given a variable
named foo with the content rem ips the template Lo{{foo}}um would render
as Lorem ipsum.
Variables can either be single (text) values or lists of values. The names of
list variables are usually plurals. A list variable is simply rendered as all
its elements concatenated together. The template ab{{list}}gh would become
abcdefgh if the elements of list are (c, d, e, f).
For the following examples these variables will be used: text=Lorem ipsum and list=(A1, B2, C3, D4).
Both types of variables can be limited using an indexing operator, either a
single index: {{list[2]}} → B2 / {{text[4]}} → e; or a range of
indices: {{list[2:3]}} → B2C3 / {{text[1:4]}} → Lore. If either index
is left out (e.g. [2:] or [:4]), it is assumed to be 1 for the first and
the length of the text/list for the second. Indices can be negative, in which
case they go backwards from the end of the variable: {{list[:-2]}} →
A1B2C3 / {{text[3:-3]}} → rem ips. If the indices given result in an
empty substitution the variable is effectively ignored. Before the index (or
prefix) is encountered, [ has to be escaped as \[ if it is part of the
variable name.
List substitutions can have a prefix, a suffix, and a separator:
{{list:pre[:]suf: | }} → pre[A1 | B2 | C3 | D4]suf. Thus : has to be
escaped at any position inside a tag. If both index and affixes/a separator
are used the tag looks like this: {{list[2:3]pre[:]suf: | }} → pre[B2 | C3]suf.
The prefix and suffix can be left empty if the substitution should only have a
separator: {{list::: \: }} → A1 : B2 : C3 : D4; and the suffix and
separator can be left out if not needed: {{list:List\:}} → List:A1B2C3D4.