Collections and maps

length: Length of a string (characters), array or map.
default: value when the input is undefined (only then; boolean=true also replaces falsy values). Not Go’s default.
default_if_empty: Go’s default: value when the input is undefined, none, 0, “”, or an empty array or map. false counts as set.
get: The map entry key, else default, else an error.
get_path: Walks path (keys and integer indices); none when a step is missing.
first: The first element, or none.
last: The last element, or none.
nth: The element at index n, or none.
keys: The keys of a map.
values: The values of a map.
pairs: [key, value] pairs of a map.
sort_keys: The map with its keys sorted; Go ranges maps in key order, Tera literals keep insertion order.
from_pairs: A map from [key, value] pairs (the inverse of pairs), for keys a map literal cannot compute: [[k, v]] | from_pairs. Keys are stringified, a later pair wins, keys sorted.
append: The array with value appended.
concat: The array followed by the elements of with.
merge: Deep merge of two maps; with wins; keys sorted.
join: Joins with sep.
delimit: Joins with sep, and last before the final element.
reverse: Reversed array or string.
unique: Removes duplicates, keeping the first.
sort: Tera’s sort (by value, or by attribute path); not locale-aware. Use sort_by for Go’s sort.
group_by: Tera’s grouping by attribute path into a map.
sort_by: Sorts by attribute (a path such as params.weight; "" or value: the elements): collation of the render’s lang, dates as instants, stable.
complement: Elements not in without (pages compared by id).
union: Elements of either array, first occurrence kept (pages by id).
intersect: Elements present in both (pages by id).
symdiff: Elements present in exactly one (pages by id).
range: Integers from start (default 0) to end (exclusive) by step_by; Go’s seq N is range(start=1, end=N+1).
querify: A URL query string from params, keys sorted.