lume/README.md

# Lume

A collection of functions for Lua, geared towards game development.


## Installation

The [lume.lua](lume.lua?raw=1) file should be dropped into an existing project
and required by it:

```lua
lume = require "lume"
```


## Function Reference

#### lume.clamp(x, min, max)
Returns the number `x` clamped between the numbers `min` and `max`

#### lume.round(x [, increment])
Rounds `x` to the nearest integer; rounds away from zero if we're midway
between two integers. If `increment` is set then the number is rounded to the
nearest increment.
```lua
lume.round(2.3) -- Returns 2
lume.round(123.4567, .1) -- Returns 123.5
```

#### lume.sign(x)
Returns `1` if `x` is 0 or above, returns `-1` when `x` is negative.

#### lume.lerp(a, b, amount)
Returns the linearly interpolated number between `a` and `b`, `amount` should
be in the range of 0 - 1; if `amount` is outside of this range it is clamped.
```lua
lume.lerp(100, 200, .5) -- Returns 150
```

#### lume.smooth(a, b, amount)
Similar to `lume.lerp()` but uses cubic interpolation instead of linear
interpolation.

#### lume.pingpong(x)
Ping-pongs the number `x` between 0 and 1.

#### lume.distance(x1, y1, x2, y2 [, squared])
Returns the distance between the two points. If `squared` is true then the
squared distance is returned -- this is faster to calculate and can still be
used when comparing distances.

#### lume.angle(x1, y1, x2, y2)
Returns the angle between the two points.

#### lume.vector(angle, magnitude)
Given an `angle` and `magnitude`, returns a vector.
```lua
local x, y = lume.vector(0, 10) -- Returns 10, 0
```

#### lume.random([a [, b]])
Returns a random number between `a` and `b`. If only `a` is supplied a number
between `0` and `a` is returned. If no arguments are supplied a random number
between `0` and `1` is returned.

#### lume.randomchoice(t)
Returns a random value from array `t`. If the array is empty an error is
raised.
```lua
lume.randomchoice({true, false}) -- Returns either true or false
```

#### lume.weightedchoice(t)
Takes the argument table `t` where the keys are the possible choices and the
value is the choice's weight. A weight should be 0 or above, the larger the
number the higher the probability of that choice being picked. If the table is
empty, a weight is below zero or all the weights are 0 then an error is raised.
```lua
lume.weightedchoice({ ["cat"] = 10, ["dog"] = 5, ["frog"] = 0 })
-- Returns either "cat" or "dog" with "cat" being twice as likely to be chosen.
```

#### lume.isarray(x)
Returns `true` if `x` is an array -- the value is assumed to be an array if it
is a table which contains a value at the index `1`. This function is used
internally and can be overridden if you wish to use a different method to detect
arrays.


#### lume.push(t, ...)
Pushes all the given values to the end of the table `t` and returns the pushed
values. Nil values are ignored.
```lua
local t = { 1, 2, 3 }
lume.push(t, 4, 5) -- `t` becomes { 1, 2, 3, 4, 5 }
```

#### lume.remove(t, x)
Removes the first instance of the value `x` if it exists in the table `t`.
Returns `x`.
```lua
local t = { 1, 2, 3 }
lume.remove(t, 2) -- `t` becomes { 1, 3 }
```

#### lume.clear(t)
Nils all the values in the table `t`, this renders the table empty. Returns
`t`.
```lua
local t = { 1, 2, 3 }
lume.clear(t) -- `t` becomes {}
```

#### lume.extend(t, ...)
Copies all the fields from the source tables to the table `t` and returns `t`.
If a key exists in multiple tables the right-most table's value is used.
```lua
local t = { a = 1, b = 2 }
lume.extend(t, { b = 4, c = 6 }) -- `t` becomes { a = 1, b = 4, c = 6 }
```

#### lume.shuffle(t)
Returns a shuffled copy of the array `t`.

#### lume.sort(t [, comp])
Returns a copy of the array `t` with all its items sorted. If `comp` is a
function it will be used to compare the items when sorting. If `comp` is a
string it will be used as the key to sort the items by.
```lua
lume.sort({ 1, 4, 3, 2, 5 }) -- Returns { 1, 2, 3, 4, 5 }
lume.sort({ {z=2}, {z=3}, {z=1} }, "z") -- Returns { {z=1}, {z=2}, {z=3} }
lume.sort({ 1, 3, 2 }, function(a, b) return a > b end) -- Returns { 3, 2, 1 }
```

#### lume.array(...)
Iterates the supplied iterator and returns an array filled with the values.
```lua
lume.array(string.gmatch("Hello world", "%a+")) -- Returns {"Hello", "world"}
```

#### lume.each(t, fn, ...)
Iterates the table `t` and calls the function `fn` on each value followed by
the supplied additional arguments; if `fn` is a string the method of that name
is called for each value. The function returns `t` unmodified.
```lua
lume.each({1, 2, 3}, print) -- Prints "1", "2", "3" on separate lines
lume.each({a, b, c}, "move", 10, 20) -- Does x:move(10, 20) on each value
```

#### lume.map(t, fn)
Applies the function `fn` to each value in table `t` and returns a new table
with the resulting values.
```lua
lume.map({1, 2, 3}, function(x) return x * 2 end) -- Returns {2, 4, 6}
```

#### lume.all(t [, fn])
Returns true if all the values in `t` table are true. If a `fn` function is
supplied it is called on each value, true is returned if all of the calls to
`fn` return true.
```lua
lume.all({1, 2, 1}, function(x) return x == 1 end) -- Returns false
```

#### lume.any(t [, fn])
Returns true if any of the values in `t` table are true. If a `fn` function is
supplied it is called on each value, true is returned if any of the calls to
`fn` return true.
```lua
lume.any({1, 2, 1}, function(x) return x == 1 end) -- Returns true
```

#### lume.reduce(t, fn [, first])
Applies `fn` on two arguments cumulative to the items of the array `t`, from
left to right, so as to reduce the array to a single value. If a `first` value
is specified the accumulator is initialised to this, otherwise the first value
in the array is used. If the array is empty and no `first` value is specified
an error is raised.
```lua
lume.reduce({1, 2, 3}, function(a, b) return a + b end) -- Returns 6
```

#### lume.unique(t)
Returns a copy of the `t` array with all the duplicate values removed.
```lua
lume.unique({2, 1, 2, "cat", "cat"}) -- Returns {1, 2, "cat"}
```

#### lume.filter(t, fn [, retainkeys])
Calls `fn` on each value of `t` table. Returns a new table with only the values
where `fn` returned true. If `retainkeys` is true the table is not treated as
an array and retains its original keys.
```lua
lume.filter({1, 2, 3, 4}, function(x) return x % 2 == 0 end) -- Returns {2, 4}
```

#### lume.reject(t, fn [, retainkeys])
The opposite of `lume.filter()`: Calls `fn` on each value of `t` table; returns
a new table with only the values where `fn` returned false. If `retainkeys` is
true the table is not treated as an array and retains its original keys.
```lua
lume.reject({1, 2, 3, 4}, function(x) return x % 2 == 0 end) -- Returns {1, 3}
```

#### lume.merge(...)
Returns a new table with all the given tables merged together. If a key exists
in multiple tables the right-most table's value is used.
```lua
lume.merge({a=1, b=2, c=3}, {c=8, d=9}) -- Returns {a=1, b=2, c=8, d=9}
```

#### lume.concat(...)
Returns a new array consisting of all the given arrays concatenated into one.
```lua
lume.concat({1, 2}, {3, 4}, {5, 6}) -- Returns {1, 2, 3, 4, 5, 6}
```

#### lume.find(t, value)
Returns the index/key of `value` in `t`. Returns `nil` if that value does not
exist in the table.
```lua
lume.find({"a", "b", "c"}, "b") -- Returns 2
```

#### lume.match(t, fn)
Returns the value and key of the value in table `t` which returns true when
`fn` is called on it. Returns `nil` if no such value exists.
```lua
lume.match({1, 5, 8, 7}, function(x) return x % 2 == 0 end) -- Returns 8, 3
```

#### lume.count(t [, fn])
Counts the number of values in the table `t`. If a `fn` function is supplied it
is called on each value, the number of times it returns true is counted.
```lua
lume.count({a = 2, b = 3, c = 4, d = 5}) -- Returns 4
lume.count({1, 2, 4, 6}, function(x) return x % 2 == 0 end) -- Returns 3
```

#### lume.slice(t [, i [, j]])
Mimics the behaviour of Lua's `string.sub`, but operates on an array rather
than a string. Creates and returns a new array of the given slice.
```lua
lume.slice({"a", "b", "c", "d", "e"}, 2, 4) -- Returns {"b", "c", "d"}
```

#### lume.first(t [, n])
Returns the first element of an array or nil if the array is empty. If `n` is
specificed an array of the first `n` elements is returned.
```lua
lume.first({"a", "b", "c"}) -- Returns "a"
```

#### lume.last(t [, n])
Returns the last element of an array or nil if the array is empty. If `n` is
specificed an array of the last `n` elements is returned.
```lua
lume.last({"a", "b", "c"}) -- Returns "c"
```

#### lume.invert(t)
Returns a copy of the table where the keys have become the values and the
values the keys.
```lua
lume.invert({a = "x", b = "y"}) -- returns {x = "a", y = "b"}
```

#### lume.pick(t, ...)
Returns a copy of the table filtered to only contain values for the given keys.
```lua
lume.pick({ a = 1, b = 2, c = 3 }, "a", "c") -- Returns { a = 1, c = 3 }
```

#### lume.keys(t)
Returns an array containing each key of the table.

#### lume.clone(t)
Returns a shallow copy of the table `t`.

#### lume.fn(fn, ...)
Creates a wrapper function around function `fn`, automatically inserting the
arguments into `fn` which will persist every time the wrapper is called. Any
arguments which are passed to the returned function will be inserted after the
already existing arguments passed to `fn`.
```lua
local f = lume.fn(print, "Hello")
f("world") -- Prints "Hello world"
```

#### lume.once(fn, ...)
Returns a wrapper function to `fn` which takes the supplied arguments. The
wrapper function will call `fn` on the first call and do nothing on any
subsequent calls.
```lua
local f = lume.once(print, "Hello")
f() -- Prints "Hello"
f() -- Does nothing
```

#### lume.memoize(fn)
Returns a wrapper function to `fn` where the results for any given set of
arguments are cached. `lume.memoize()` is useful when used on functions with
slow-running computations.
```lua
fib = lume.memoize(function(n) return n < 2 and n or fib(n-1) + fib(n-2) end)
```

#### lume.combine(...)
Creates a wrapper function which calls each supplied argument in the order they
were passed to `lume.combine()`; nil arguments are ignored. The wrapper
function passes its own arguments to each of its wrapped functions when it is
called.
```lua
local f = lume.combine(function(a, b) print(a + b) end,
                       function(a, b) print(a * b) end)
f(3, 4) -- Prints "7" then "12" on a new line
```

#### lume.call(fn, ...)
Calls the given function with the provided arguments and returns its values. If
`fn` is `nil` then no action is performed and the function returns `nil`.
```lua
lume.call(print, "Hello world") -- Prints "Hello world"
```

#### lume.time(fn, ...)
Inserts the arguments into function `fn` and calls it. Returns the time in
seconds the function `fn` took to execute followed by `fn`'s returned values.
```lua
lume.time(function(x) return x end, "hello") -- Returns 0, "hello"
```

#### lume.lambda(str)
Takes a string lambda and returns a function. `str` should be a list of
comma-separated parameters, followed by `->`, followed by the expression which
will be evaluated and returned.
```lua
local f = lume.lambda "x,y -> 2*x+y"
f(10, 5) -- Returns 25
```

#### lume.serialize(x)
Serializes the argument `x` into a string which can be loaded again using
`lume.deserialize()`. Only booleans, numbers, tables and strings can be
serialized. Circular references will result in an error; all nested tables are
serialized as unique tables.
```lua
lume.serialize({a = "test", b = {1, 2, 3}, false})
-- Returns "{[1]=false,["a"]="test",["b"]={[1]=1,[2]=2,[3]=3,},}"
```

#### lume.deserialize(str)
Deserializes a string created by `lume.serialize()` and returns the resulting
value. This function should not be run on an untrusted string.
```lua
lume.deserialize("{1, 2, 3}") -- Returns {1, 2, 3}
```

#### lume.split(str [, sep])
Returns an array of the words in the string `str`. If `sep` is provided it is
used as the delimiter, consecutive delimiters are not grouped together and will
delimit empty strings.
```lua
lume.split("One two three") -- Returns {"One", "two", "three"}
lume.split("a,b,,c", ",") -- Returns {"a", "b", "", "c"}
```

#### lume.trim(str [, chars])
Trims the whitespace from the start and end of the string `str` and returns the
new string. If a `chars` value is set the characters in `chars` are trimmed
instead of whitespace.
```lua
lume.trim("  Hello  ") -- Returns "Hello"
```

#### lume.wordwrap(str [, limit])
Returns `str` wrapped to `limit` number of characters per line, by default
`limit` is `72`. `limit` can also be a function which when passed a string,
returns `true` if it is too long for a single line.
```lua
-- Returns "Hello world\nThis is a\nshort string"
lume.wordwrap("Hello world. This is a short string", 14)
```

#### lume.format(str [, vars])
Returns a formatted string. The values of keys in the table `vars` can be
inserted into the string by using the form `"{key}"` in `str`; numerical keys
can also be used.
```lua
lume.format("{b} hi {a}", {a = "mark", b = "Oh"}) -- Returns "Oh hi mark"
lume.format("Hello {1}!", {"world"}) -- Returns "Hello world!"
```

#### lume.trace(...)
Prints the current filename and line number followed by each argument separated
by a space.
```lua
-- Assuming the file is called "example.lua" and the next line is 12:
lume.trace("hello", 1234) -- Prints "example.lua:12: hello 1234"
```

#### lume.dostring(str)
Executes the lua code inside `str`.
```lua
lume.dostring("print('Hello!')") -- Prints "Hello!"
```

#### lume.uuid()
Generates a random UUID string; version 4 as specified in
[RFC 4122](http://www.ietf.org/rfc/rfc4122.txt).

#### lume.hotswap(modname)
Reloads an already loaded module in place, allowing you to immediately see the
effects of code changes without having to restart the program. `modname` should
be the same string used when loading the module with require(). In the case of
an error the global environment is restored and `nil` plus an error message is
returned.
```lua
lume.hotswap("lume") -- Reloads the lume module
assert(lume.hotswap("inexistant_module")) -- Raises an error
```

#### lume.ripairs(t)
Performs the same function as `ipairs()` but iterates in reverse; this allows
the removal of items from the table during iteration without any items being
skipped.
```lua
-- Prints "3->c", "2->b" and "1->a" on separate lines
for i, v in lume.ripairs({ "a", "b", "c" }) do
  print(i .. "->" .. v)
end
```

#### lume.color(str [, mul])
Takes color string `str` and returns 4 values, one for each color channel (`r`,
`g`, `b` and `a`). By default the returned values are between 0 and 1; the
values are multiplied by the number `mul` if it is provided.
```lua
lume.color("#ff0000")               -- Returns 1, 0, 0, 1
lume.color("rgba(255, 0, 255, .5)") -- Returns 1, 0, 1, .5
lume.color("#00ffff", 256)          -- Returns 0, 256, 256, 256
lume.color("rgb(255, 0, 0)", 256)   -- Returns 256, 0, 0, 256
```

#### lume.chain(value)
Returns a wrapped object which allows chaining of lume functions. The function
result() should be called at the end of the chain to return the resulting
value.
```lua
lume.chain({1, 2, 3, 4})
  :filter(function(x) return x % 2 == 0 end)
  :map(function(x) return -x end)
  :result() -- Returns { -2, -4 }
```
The table returned by the `lume` module, when called, acts in the same manner
as calling `lume.chain()`.
```lua
lume({1, 2, 3}):each(print) -- Prints 1, 2 then 3 on separate lines
```

## Iteratee functions
Several lume functions allow a `table`, `string` or `nil` to be used in place
of their iteratee function argument. The functions that provide this behaviour
are: `map()`, `all()`, `any()`, `filter()`, `reject()`, `match()` and
`count()`.

If the argument is `nil` then each value will return itself.
```lua
lume.filter({ true, true, false, true }, nil) -- { true, true, true }
```

If the argument is a `string` then each value will be assumed to be a table,
and will return the value of the key which matches the string.
``` lua
local t = {{ z = "cat" }, { z = "dog" }, { z = "owl" }}
lume.map(t, "z") -- Returns { "cat", "dog", "owl" }
```

If the argument is a `table` then each value will return `true` or `false`,
depending on whether the values at each of the table's keys match the
collection's value's values.
```lua
local t = {
  { age = 10, type = "cat" },
  { age = 8,  type = "dog" },
  { age = 10, type = "owl" },
}
lume.count(t, { age = 10 }) -- returns 2
```


## License

This library is free software; you can redistribute it and/or modify it under
the terms of the MIT license. See [LICENSE](LICENSE) for details.