# erlquad #
Copyright (c) 2016 Guilherme Andrade
__Version:__ 1.1.1
__Authors:__ Guilherme Andrade ([`erlquad(at)gandrade(dot)net`](mailto:erlquad(at)gandrade(dot)net)).
`erlquad`: A simple Erlang quadtree implementation
---------
`erlquad` is a straightforward Erlang implementation of [quadtrees](https://en.wikipedia.org/wiki/Quadtree), supporting both bounding-box outlines as well as precise coordinates for small enough objects.
It exposes functions for fetching, folding and any'ing (with boolean predicate) particular areas of interest as well as all contained objects. Deeplist versions of fetching methods are also included for when there's no need to concatenate the intermediate results and thus avoid the overhead of doing so.
Buckets have unlimited capacity and depth is fixed on initialization.
```erlang
Object1 = #big_square{ x = 1000, y = 750, side = 10 },
Object2 = #tiny_circle{ x = 3000, y = 1000 },
Object3 = #tiny_circle{ x = 3000, y = 2000 },
GetOutline = fun (#tiny_circle{ x = X, y = Y }) ->
{X, Y};
(#big_square{ x = X, y = Y, side = S }) ->
{X - S/2, Y - S/2, X + S/2, Y + S/2}
end,
IsSquare = fun (#tiny_circle{}) -> false;
(#big_square{}) -> true
end,
CountCirclesFold = fun (#tiny_circle{}, Acc) -> Acc + 1;
(#big_square{}, Acc) -> Acc
end,
Q1 = erlquad:new(0, 0, 4000, 3000, 3), % Left, Bottom, Right, Top, Depth
Q2 = erlquad:objects_add([Object1, Object2, Object3], GetOutline, Q1),
erlquad:area_query(0, 0, 1999, 2999, Q2), % [#big_square{...}]
erlquad:area_query(2000, 0, 3999, 2999, Q2), % [#tiny_circle{...}, #tiny_circle{...}]
erlquad:area_query(0, 0, 3999, 2999, Q2), % [#big_square{...}, #tiny_circle{...}, #tiny_circle{...}]
erlquad:area_query_deep(0, 0, 3999, 2999, Q2), % [[], [[#big_square{...}, [[], [], ...]], [[[], ...[]]]]]
erlquad:area_query_any(IsSquare, 0, 0, 1999, 1499, Q2), % true
erlquad:area_query_any(IsSquare, 2000, 1500, 3999, 2999, Q2), % false
erlquad:area_query_fold(CountCirclesFold, 0, 2000, 0, 3999, 2999, Q2), % 2
erlquad:area_query_fold(CountCirclesFold, 0, 2000, 0, 3999, 1499, Q2), % 1
erlquad:area_query_fold(CountCirclesFold, 0, 2000, 0, 3999, 749, Q2), % 0
erlquad:objects_any(IsSquare, Q2), % true
erlquad:objects_fold(CountCirclesFold, 0, Q2), % 2
erlquad:objects_all(Q2), % [#big_square{...}, #tiny_circle{...}, #tiny_circle{...}]
erlquad:objects_deep_all(Q2), % [[], [[#big_square{...}, [[], [], ...]], [[[], ...[]]]]]
```
Define 'COMPILE_NATIVE_ERLQUAD' (e.g. "rebar compile -DCOMPILE_NATIVE_ERLQUAD") for HiPE compilation.
## Modules ##
<table width="100%" border="0" summary="list of modules">
<tr><td><a href="https://github.com/g-andrade/erlquad/blob/master/doc/erlquad.md" class="module">erlquad</a></td></tr></table>
