Coming from Liquid

Vascula's syntax is close to Liquid's, so most templates read the same. It is its own language, stricter than Liquid in a few places. This page lists every difference.

#Behavior

	Liquid	Vascula
Output escaping	Off; use `escape`	Always on; no way to turn it off
`raw` filter, `{% raw %}`	Available	Not available
Reading an unknown name	Prints nothing	Error, unless the application allows that root
Unknown filter	Ignored or error, depending on mode	Error
`"5" > 3`	Compares somehow	Error: ordering needs two numbers or two strings
`"5" == 5`	False	True: a numeric string equals its number
`10 \| divided_by: 4`	`2` (integer division)	`2.5`
Integers	Arbitrary size	Exact 64-bit integers
Variables assigned in a block	Global	Global (the same)
`include`	Shares the caller's variables	Removed; `render` only, with its own scope
`render` with a variable name	Not allowed	Not allowed (the same)
`and` / `or`	Evaluate right to left	Evaluate left to right, short-circuit, and return an operand
JSON inside an attribute	Breaks the attribute	Escaped for the attribute automatically
Errors	Often rendered inline	Returned to the application with line and column
Resource use	Depends on the host	Bounded: work, output, value size, depth

#Tags

Liquid tag	Vascula
`if`, `elsif`, `else`, `unless`	Same. `unless` has no `elsif`.
`case`, `when`	Same, including `when a, b` and `when a or b`.
`for` with `limit`, `offset`, `reversed`, `else`	Same. Ranges `(1..n)` work.
`forloop.*`	Same properties, including `parentloop`.
`break`, `continue`, `cycle`	Same. Cycle groups (`cycle "g": ...`) are not supported.
`assign`, `capture`	Same.
`comment`, `{% # %}`	`{% comment %}` and `{# ... #}`.
`increment`, `decrement`	Not supported; use `assign` with `plus`.
`tablerow`	Not supported; use `for` with `forloop`.
`liquid`, `echo`	Not supported.
`render`	Same idea; arguments with `name: value`. `with` and `for` forms are not supported.
`include`	Not supported.
`raw`	Not supported.
Shopify `form`, `section`, `schema`, `style`, `javascript`, `paginate`	Not part of the language; an application can add its own tags.

#Filters

These Liquid filters exist in Vascula with the same meaning: abs, append, at_least, at_most, capitalize, ceil, compact, concat, date, default, divided_by (but see the table above), downcase, escape, escape_once, first, floor, join, last, lstrip, map, minus, modulo, newline_to_br, plus, prepend, remove, remove_first, replace, replace_first, reverse, round, rstrip, size, slice, sort, sort_natural, split, strip, strip_html, strip_newlines, sum, times, truncate, truncatewords, uniq, upcase, url_decode, url_encode, where.

Vascula adds json.

Not available: raw, base64_*, url_escape, remove_last, replace_last, find, find_index, has, reject, group_by, and Shopify's commerce filters (money, img_url, t and others). Applications provide their own filters for formatting money, building URLs and translating text.

#Porting a template

Compile it. Every unsupported tag or syntax error is reported with its line and column.
Remove | raw and {% raw %}. If something must print HTML, the application has to pass it as trusted HTML.
Replace include with render, passing what the child needs as arguments.
Render it with the data it needs and fix each undeclared name error: either it is a typo, or the application must allow that root.
Check divisions: unlike Liquid, divided_by does not truncate integer division; add | floor where you relied on that.