Topic `tutorial.md`

Moses: a utility-belt library for Lua

Moses is a Lua utility library which provides support for functional programming. It complements built-in Lua functions, making easier common operations on tables, arrays, lists, collections, objects, and a lot more.
Moses was deeply inspired by Underscore.js.

Adding Moses to your project

Moses' API

 * [Table functions](#table)
 * [Array functions](#array)
 * [Utility functions](#utility)
 * [Object functions](#object)
 * [Chaining](#chaining)
 * [Import](#import)

Adding Moses to your project

Drop the file moses.lua into your project and add it to your code with the require function:

local _ = require ("moses")

Note: Lua purists tend to use "_" to design a "dummy variable". Here, the usage of this underscore is quite idiomatic and refers to the name Underscore, the JS library from which *Moses takes inspiration*.

[⬆]

Moses' API

Moses' consists of a large set of functions that can be classified into four categories:

Table functions, which are mostly meant for tables, i.e Lua tables which contains both an array-part and/or a map-part,
Array functions, meant for array lists (or sequences),
Utility functions,
Object functions, meant for instances/classes.

[⬆]

Table functions

each (t, f, ...)

*Aliases: _.forEach*.

Iterates over each key-value pair in table.

_.each({1,2,3},print)

-- => 1 1
-- => 2 2
-- => 3 3

The table can be map-like (array part and hash-part).

_.each({one = 1, two = 2, three = 3},print)

-- => one 1
-- => two 2
-- => three 3

Can index and assign in an outer table or in the passed-in table:

t = {'a','b','c'}
_.each(t,function(i,v)
  t[i] = v:rep(2)
  print(t[i])
end)

-- => 1 aa
-- => 2 bb
-- => 3 cc

eachi (t, f, ...)

*Aliases: _.forEachi*.

Iterates only on integer keys in a sparse array table.

_.eachi({1,2,3},print)

-- => 1 1
-- => 2 2
-- => 3 3

The given array can be sparse, or even have a hash-like part.

local t = {a = 1, b = 2, [0] = 1, [-1] = 6, 3, x = 4, 5}
_.eachi(t,function(i,v)
  print(i,v)
end)

-- => -1 6
-- => 0 1
-- => 1 3
-- => 2 5

at (t, ...)

Collects all values at some specific keys and returns them in an array.

local t = {4,5,6}
_.at(t,1,3) -- => "{4,6}"

local t = {a = 4, bb = true, ccc = false}
_.at(t,'a', 'ccc') -- => "{4, false}"

count (t, value)

Counts the number of occurences of a given value in a table.

_.count({1,1,2,3,3,3,2,4,3,2},1) -- => 2
_.count({1,1,2,3,3,3,2,4,3,2},2) -- => 2
_.count({1,1,2,3,3,3,2,4,3,2},3) -- => 4
_.count({false, false, true},false) -- => 2
_.count({false, false, true},true) -- => 1

Returns the size of the list in case no value was provided.

_.count({1,1,2,3,3}) -- => 5

countf (t, f, ...)

Count the number of occurences of all values passing an iterator test.

_.countf({1,2,3,4,5,6}, function(i,v)
  return v%2==0
end) -- => 3

_.countf({print, pairs, os, assert, ipairs}, function(i,v)
  return type(v)=='function'
end) -- => 4

cycle (t, n)

*Aliases: _.loop*.

Returns a function which iterates on each key-value pair in a given table (similarly to _.each), except that it restarts iterating again n times. If n is not provided, it defaults to 1.

local t = {'a,'b','c'}
for k,v in _.cycle(t, 2) do
  print(k,v)
end

-- => 1 'a'
-- => 2 'b'
-- => 3 'c'
-- => 1 'a'
-- => 2 'b'
-- => 3 'c'

Supports array-like tables and map-like tables.

local t = {x = 1, y = 2, z = 3}
for k,v in _.cycle(t) do
  print(k,v)
end

-- => y    2
-- => x 1
-- => z 3

map (t, f, ...)

*Aliases: _.collect*.

Executes a function on each key-value pairs.

_.map({1,2,3},function(i,v)
  return v+10
end)) -- => "{11,12,13}"

_.map({a = 1, b = 2},function(k,v)
  return k..v
end) -- => "{a = 'a1', b = 'b2'}"

reduce (t, f, state)

*Aliases: _.inject, _.foldl*.

Can sums all values in a table.

_.reduce({1,2,3,4},function(memo,v)
  return memo+v
end) -- => 10

Or concatenates all values.

_.reduce({'a','b','c','d'},function(memo,v)
  return memo..v
end) -- => abcd

reduceRight (t, f, state)

*Aliases: _.injectr, _.foldr*.

Similar to _.reduce, but performs from right to left.

local initial_state = 256
_.reduceRight({1,2,4,16},function(memo,v)
  return memo/v
end,initial_state) -- => 2

mapReduce (t, f, state)

*Aliases: _.mapr*.

Reduces while saving intermediate states.

_.mapReduce({'a','b','c'},function(memo,v)
  return memo..v
end) -- => "{'a', 'ab', 'abc'}"

mapReduceRight (t, f, state)

*Aliases: _.maprr*.

Reduces from right to left, while saving intermediate states.

_.mapReduceRight({'a','b','c'},function(memo,v)
  return memo..v
end) -- => "{'c', 'cb', 'cba'}"

include (t, value)

*Aliases: _.any, _.some*.

Looks for a value in a table.

_.include({6,8,10,16,29},16) -- => true
_.include({6,8,10,16,29},1) -- => false

local complex_table = {18,{2,{3}}}
local collection = {6,{18,{2,6}},10,{18,{2,{3}}},29}
_.include(collection, complex_table) -- => true

Handles iterator functions.

local function isUpper(v) return v:upper()== v end
_.include({'a','B','c'},isUpper) -- => true

detect (t, value)

Returns the index of a value in a table.

_.detect({6,8,10,16},8) -- => 2
_.detect({nil,true,0,true,true},false) -- => nil

local complex_table = {18,{2,6}}
local collection = {6,{18,{2,6}},10,{18,{2,{3}}},29}
_.detect(collection, complex_table) -- => 2

Handles iterator functions.

local function isUpper(v)
  return v:upper()==v
end
_.detect({'a','B','c'},isUpper) -- => 2

contains (t, value)

Returns true if the passed-in value was found in a given table.

_.contains({6,8,10,16},8) -- => true
_.contains({nil,true,0,true,true},false) -- => false

It can lookup for objects, and accepts iterator functions aswell:

_.contains({6,{18,{2,6}},10,{18,{2,{3}}},29},{18,{2,6}}) -- => true

_.contains({'a','B','c'}, function(array_value)
  return (array_value:upper() == array_value)
end) -- => true

findWhere (t, props)

Looks through a table and returns the first value that matches all of the key-value pairs listed in properties.

local a = {a = 1, b = 2, c = 3}
local b = {a = 2, b = 3, d = 4}
local c = {a = 3, b = 4, e = 5}
_.findWhere({a, b, c}, {a = 3, b = 4}) == c -- => true

select (t, f, ...)

*Aliases: _.filte*.

Collects values passing a validation test.

-- Even values
_.select({1,2,3,4,5,6,7}, function(key,value)
  return (value%2==0)
end) -- => "{2,4,6}"

-- Odd values
_.select({1,2,3,4,5,6,7}, function(key,value)
  return (value%2~=0)
end) -- => "{1,3,5,7}"

reject (t, f, ...)

*Aliases: _.reject*.

Removes all values failing a validation test:

_.reject({1,2,3,4,5,6,7}, function(key,value)
  return (value%2==0)
end) -- => "{1,3,5,7}"

_.reject({1,2,3,4,5,6,7}, function(key,value)
  return (value%2~=0)
end) -- => "{2,4,6}"

all (t, f, ...)

*Aliases: _.every*.

Checks whether or not all elements pass a validation test.

_.all({2,4,6}, function(key,value)
  return (value%2==0)
end) -- => true

invoke (t, method, ...)

Invokes a given function on each value in a table

_.invoke({'a','bea','cdhza'},string.len) -- => "{1,3,5}"

Can reference the method of the same name in each value.

local a = {}
function a:call() return 'a' end
local b, c, d = {}, {}, {}
b.call, c.call, d.call = a.call, a.call, a.call

_.invoke({a,b,c,d},'call') -- => "{'a','a','a','a'}"

pluck (t, property)

Fetches all values indxed with specific key in a table of objects.

local peoples = {
  {name = 'John', age = 23},{name = 'Peter', age = 17},
  {name = 'Steve', age = 15},{age = 33}}

_.pluck(peoples,'age') -- => "{23,17,15,33}"
_.pluck(peoples,'name') -- => "{'John', 'Peter', 'Steve'}"

max (t, transform, ...)

Returns the maximum value in a collection.

_.max {1,2,3} -- => 3
_.max {'a','b','c'} -- => 'c'

Can take an iterator function to extract a specific property.

local peoples = {
  {name = 'John', age = 23},{name = 'Peter', age = 17},
  {name = 'Steve', age = 15},{age = 33}}
_.max(peoples,function(people) return people.age end) -- => 33

min (t, transform, ...)

Returns the minimum value in a collection.

_.min {1,2,3} -- => 1
_.min {'a','b','c'} -- => 'a'

Can take an iterator function to extract a specific property.

local peoples = {
  {name = 'John', age = 23},{name = 'Peter', age = 17},
  {name = 'Steve', age = 15},{age = 33}}
_.min(peoples,function(people) return people.age end) -- => 15

shuffle (t, seed)

Shuffles a collection.

local list = _.shuffle {1,2,3,4,5,6} -- => "{3,2,6,4,1,5}"
_.each(list,print)

same (a, b)

Tests whether or not all values in each of the passed-in tables exists in both tables.

local a = {'a','b','c','d'}
local b = {'b','a','d','c'}
_.same(a,b) -- => true

b[#b+1] = 'e'
_.same(a,b) -- => false

sort (t, comp)

Sorts a collection.

_.sort({'b','a','d','c'}) -- => "{'a','b','c','d'}"

Handles custom comparison functions.

_.sort({'b','a','d','c'}, function(a,b)
  return a:byte() > b:byte()
end) -- => "{'d','c','b','a'}"

groupBy (t, iter, ...)

Groups values in a collection depending on their return value when passed to a predicate test.

_.groupBy({0,1,2,3,4,5,6},function(i,value)
  return value%2==0 and 'even' or 'odd'
end) -- => "{odd = {1,3,5}, even = {0,2,4,6}}"

_.groupBy({0,'a',true, false,nil,b,0.5},function(i,value)
  return type(value)
end) -- => "{number = {0,0.5}, string = {'a'}, boolean = {true, false}}"

countBy (t, iter, ...)

Splits a table in subsets and provide the count for each subset.

_.countBy({0,1,2,3,4,5,6},function(i,value)
  return value%2==0 and 'even' or 'odd'
end) -- => "{odd = 3, even = 4}"

size (...)

When given a table, provides the count for the very number of values in that table.

_.size {1,2,3} -- => 3
_.size {one = 1, two = 2} -- => 2

When given a vararg list of argument, returns the count of these arguments.

_.size(1,2,3) -- => 3
_.size('a','b',{}, function() end) -- => 4

containsKeys (t, other)

Checks whether a table has all the keys existing in another table.

_.contains({1,2,3,4},{1,2,3}) -- => true
_.contains({1,2,'d','b'},{1,2,3,5}) -- => true
_.contains({x = 1, y = 2, z = 3},{x = 1, y = 2}) -- => true

sameKeys (tA, tB)

Checks whether both tables features the same keys:

_.sameKeys({1,2,3,4},{1,2,3}) -- => false
_.sameKeys({1,2,'d','b'},{1,2,3,5}) -- => true
_.sameKeys({x = 1, y = 2, z = 3},{x = 1, y = 2}) -- => false

[⬆]

Array functions

toArray (...)

Converts a vararg list of arguments to an array.

_.toArray(1,2,8,'d','a',0) -- => "{1,2,8,'d','a',0}"

find (array, value, from)

Looks for a value in a given array and returns the position of the first occurence.

_.find({{4},{3},{2},{1}},{3}) -- => 2

It can also start the search at a specific position in the array:

-- search value 4 starting from index 3
_.find({1,4,2,3,4,5},4,3) -- => 5

reverse (array)

Reverses an array.

_.reverse({1,2,3,'d'}) -- => "{'d',3,2,1}"

selectWhile (array, f, ...

*Aliases: _.takeWhile*.

Collects values as long as they pass a given test. Stops on the first non-passing test.

_.selectWhile({2,4,5,8}, function(i,v)
  return v%2==0
end) -- => "{2,4}"

dropWhile (array, f, ...

*Aliases: _.rejectWhile*.

Removes values as long as they pass a given test. Stops on the first non-passing test.

_.dropWhile({2,4,5,8}, function(i,v)
  return v%2==0
end) -- => "{5,8}"

sortedIndex (array, value, comp, sort)

Returns the index at which a value should be inserted to preserve order.

_.sortedIndex({1,2,3},4) -- => 4

Can take a custom comparison functions.

local comp = function(a,b) return a<b end
_.sortedIndex({-5,0,4,4},3,comp) -- => 3

indexOf (array, value)

Returns the index of a value in an array.

_.indexOf({1,2,3},2) -- => 2

lastIndexOf (array, value)

Returns the index of the last occurence of a given value in an array.

_.lastIndexOf({1,2,2,3},2) -- => 3

addTop (array, ...)

Adds given values at the top of an array. The latter values bubbles at the top.

local array = {1}
_.addTop(array,1,2,3,4) -- => "{4,3,2,1,1}"

push (array, ...)

Adds given values at the end of an array.

local array = {1}
_.push(array,1,2,3,4) -- => "{1,1,2,3,4}"

pop (array, n)

*Aliases: _.shift*.

Removes and returns the first value in an array.

local array = {1,2,3}
local pop = _.pop(array) -- => "pop = 1", "array = {2,3}"

unshift (array, n)

Removes and returns the last value in an array.

local array = {1,2,3}
local value = _.unshift(array) -- => "value = 3", "array = {1,2}"

pull (array, ...)

*Aliases: _.remove*.

Removes all provided values from a given array.

_.pull({1,2,1,2,3,4,3},1,2,3) -- => "{4}"

removeRange (array, start, finish)

*Aliases: _.rmRange, _.chop*.

Trims out all values index within a range.

local array = {1,2,3,4,5,6,7,8,9}
_.removeRange(array, 3,8) -- => "{1,2,9}"

chunk (array, f, ...)

Iterates over an array aggregating consecutive values in subsets tables, on the basis of the return value of f(key,value,...). Consecutive elements which return the same value are aggregated together.

local t = {1,1,2,3,3,4}
_.chunk(t, function(k,v) return v%2==0 end) -- => "{{1,1},{2},{3,3},{4}}"

slice (array, start, finish)

*Aliases: _.sub*.

Slices and returns a part of an array.

local array = {1,2,3,4,5,6,7,8,9}
_.slice(array, 3,6) -- => "{3,4,5,6}"

first (array, n)

*Aliases: _.head, _.take*.

Returns the first N elements in an array.

local array = {1,2,3,4,5,6,7,8,9}
_.first(array,3) -- => "{1,2,3}"

initial (array, n)

Excludes the last N elements in an array.

local array = {1,2,3,4,5,6,7,8,9}
_.initial(array,5) -- => "{1,2,3,4}"

last (array, n)

*Aliases: _.skip*.

Returns the last N elements in an array.

local array = {1,2,3,4,5,6,7,8,9}
_.last(array,3) -- => "{7,8,9}"

rest (array, index)

*Aliases: _.tail*.

Trims out all values indexed before index.

local array = {1,2,3,4,5,6,7,8,9}
_.rest(array,6) -- => "{6,7,8,9}"

compact (array)

Trims out all falsy values.

_.compact {a,'aa',false,'bb',true} -- => "{'aa','bb',true}"

flatten (array, shallow)

Flattens a nested array.

_.flatten({1,{2,3},{4,5,{6,7}}}) -- => "{1,2,3,4,5,6,7}"

When given arg "shallow", flatten only at the first level.

_.flatten({1,{2},{{3}}},true) -- => "{1,{2},{{3}}}"

difference (array, array2)

*Aliases: _.without, _.diff*.

Returns values in the given array not present in a second array.

local array = {1,2,'a',4,5}
_.difference(array,{1,'a'}) -- => "{2,4,5}"

union (...)

Produces a duplicate-free union of all passed-in arrays.

local A = {'a'}
local B = {'a',1,2,3}
local C = {2,10}
_.union(A,B,C) -- => "{'a',1,2,3,10}"

intersection (array, ...)

Returns the intersection (common-part) of all passed-in arrays:

local A = {'a'}
local B = {'a',1,2,3}
local C = {2,10,1,'a'}
_.intersection(A,B,C) -- => "{'a',2,1}"

symmetricDifference (array, array2)

*Aliases: _.symdiff,_.xor*.

Returns values in the first array not present in the second and also values in the second array not present in the first one.

local array = {1,2,3}
local array2 = {1,4,5}
_.symmetricDifference(array, array2) -- => "{2,3,4,5}"

unique (array)

*Aliases: _.uniq*.

Makes an array duplicate-free.

_.unique {1,1,2,2,3,3,4,4,4,5} -- => "{1,2,3,4,5}"

isunique (array)

*Aliases: _.isuniq*.

Checks if a given array contains no duplicate value.

_.isunique({1,2,3,4,5}) -- => true
_.isunique({1,2,3,4,4}) -- => false

zip (...)

Zips values from different arrays, on the basis on their common keys.

local names = {'Bob','Alice','James'}
local ages = {22, 23}
_.zip(names,ages) -- => "{{'Bob',22},{'Alice',23},{'James'}}"

append (array, other)

Appends two arrays.

_.append({1,2,3},{'a','b'}) -- => "{1,2,3,'a','b'}"

interleave (...)

Interleaves values from passed-in arrays.

t1 = {1, 2, 3}
t2 = {'a', 'b', 'c'}
_.interleave(t1, t2) -- => "{1,'a',2,'b',3,'c'}"

interpose (value, array)

Interposes a value between consecutive values in an arrays.

_.interleave('a', {1,2,3}) -- => "{1,'a',2,'a',3}"

range (...)

Generates an arithmetic sequence.

_.range(1,4) -- => "{1,2,3,4}"

In case a single value is provided, it generates a sequence from 0 to that value.

_.range(3) -- => "{0,1,2,3}"

The incremental step can also be provided as third argument.

_.range(0,2,0.7) -- => "{0,0.7,1.4}"

rep (value, n)

Generates a list of n repetitions of a value.

_.rep(4,3) -- => "{4,4,4}"

partition (array, n)

*Aliases: _.part*.

Returns an iterator function for partitions of a given array.

local t = {1,2,3,4,5,6}
for p in _.partition(t,2) do
  print(table.concat(p, ','))
end

-- => 1,2
-- => 3,4
-- => 5,6

permutation (array)

*Aliases: _.perm*.

Returns an iterator function for permutations of a given array.

t = {'a','b','c'}
for p in _.permutation(t) do
  print(table.concat(p))
end

-- => 'bca'
-- => 'cba'
-- => 'cab'
-- => 'acb'
-- => 'bac'
-- => 'abc'

invert (array)

*Aliases: _.mirror*.

Switches key-value pairs:

_.invert {'a','b','c'} -- => "{a=1, b=2, c=3}"

concat (array, sep, i, j)

*Aliases: _.join*.

Concatenates a given array values:

_.concat({'a',1,0,1,'b'}) -- => 'a101b'

[⬆]

Utility functions

identity (value)

Returns the passed-in value.
This function is internally used as a default transformation function.

_.identity(1)-- => 1
_.identity(false) -- => false
_.identity('hello!') -- => 'hello!'

once (f)

Produces a function that runs only once. Successive calls to this function will still yield the same input.

local sq = _.once(function(a) return a*a end)
sq(1) -- => 1
sq(2) -- => 1
sq(3) -- => 1
sq(4) -- => 1
sq(5) -- => 1

memoize (f, hash)

*Aliases: _.cache*.

Memoizes a slow-running function. It caches the result for a specific input, so that the next time the function is called with the same input, it will lookup the result in its cache, instead of running again the function body.

local function fibonacci(n)
  return n < 2 and n or fibonacci(n-1)+fibonacci(n-2)
end
local mem_fibonacci = _.memoize(fibonacci)
fibonacci(20) -- => 6765 (but takes some time)
mem_fibonacci(20) -- => 6765 (takes less time)

after (f, count)

Produces a function that will respond only after a given number of calls.

local f = _.after(_.identity,3)
f(1) -- => nil
f(2) -- => nil
f(3) -- => 3
f(4) -- => 4

compose (...)

Composes functions. Each function consumes the return value of the one that follows.

local function f(x) return x^2 end
local function g(x) return x+1 end
local function h(x) return x/2 end
local compositae = _.compose(f,g,h)
compositae(10) -- => 36
compositae(20) -- => 121

pipe (value, ...)

Pipes a value through a series of functions.

local function f(x) return x^2 end
local function g(x) return x+1 end
local function h(x) return x/2 end
_.pipe(10,f,g,h) -- => 36
_.pipe(20,f,g,h) -- => 121

complement (f)

Returns a function which returns the logical complement of a given function.

_.complement(function() return true end)() -- => false

juxtapose (value, ...)

*Aliases: _.juxt*.

Calls a sequence of functions with the same input.

local function f(x) return x^2 end
local function g(x) return x+1 end
local function h(x) return x/2 end
_.juxtapose(10, f, g, h) -- => 100, 11, 5

wrap (f, wrapper)

Wraps a function inside a wrapper. Allows the wrapper to execute code before and after function run.

local greet = function(name) return "hi: " .. name end
local greet_backwards = _.wrap(greet, function(f,arg)
  return f(arg) ..'\nhi: ' .. arg:reverse()
end)
greet_backwards('John')

-- => hi: John
-- => hi: nhoJ

times (n, iter, ...)

Calls a given function n times.

local f = ('Lua programming'):gmatch('.')
_.times(3,f) -- => {'L','u','a'}

bind (f, v)

Binds a value to be the first argument to a function.

local sqrt2 = _.bind(math.sqrt,2)
sqrt2() -- => 1.4142135623731

bindn (f, ...)

Binds a variable number of values to be the first arguments to a function.

local function out(...) return table.concat {...} end
local out = _.bindn(out,'OutPut',':',' ')
out(1,2,3) -- => OutPut: 123
out('a','b','c','d') -- => OutPut: abcd

uniqueId (template, ...)

*Aliases: _.uid*.

Returns an unique integer ID.

_.uniqueId() -- => 1

Can handle string templates for formatted output.

_.uniqueId('ID%s') -- => 'ID2'

Or a function, for the same purpose.

local formatter = function(ID) return '$'..ID..'$' end
_.uniqueId(formatter) -- => '$ID1$'

[⬆]

Object functions

keys (obj)

Collects the names of an object attributes.

_.keys({1,2,3}) -- => "{1,2,3}"
_.keys({x = 0, y = 1}) -- => "{'y','x'}"

values (obj)

Collects the values of an object attributes.

_.values({1,2,3}) -- => "{1,2,3}"
_.values({x = 0, y = 1}) -- => "{1,0}"

toBoolean (value)

Converts a given value to a boolean.

_.toBoolean(true) -- => true
_.toBoolean(false) -- => false
_.toBoolean(nil) -- => false
_.toBoolean({}) -- => true
_.toBoolean(1) -- => true

extend (destObj, ...)

Extends a destination object with the properties of some source objects.

_.extend({},{a = 'b', c = 'd'}) -- => "{a = 'b', c = 'd'}"

functions (obj, recurseMt)

*Aliases: _.methods*.

Returns all functions names within an object.

_.functions(coroutine) -- => "{'create','resume','running','status','wrap','yield'}"

clone (obj, shallow)

Clones a given object.

local obj = {1,2,3}
local obj2 = _.clone(obj)
print(obj2 == obj) -- => false
print(_.isEqual(obj2, obj)) -- => true

tap (obj, f, ...)

Invokes a given interceptor function on some object, and then returns the object itself. Useful to tap into method chaining to hook intermediate results. The pased-interceptor is prototyped as f(obj,...).

local v = _.chain({1,2,3,4,5,6,7,8,9,10)
  :filter(function(k,v) return v%2~=0 end) -- filters even values
  :tap(function(v) print('Max is', _.max(v) end) -- Tap max values
  :map(function(k,v) return k^2)
  :value() -- =>    Max is 9

has (obj, key)

Checks if an object has a given attribute.

_.has(_,'has') -- => true
_.has(coroutine,'resume') -- => true
_.has(math,'random') -- => true

pick (obj, ...)

*Aliases: _.choose*.

Collects whilelisted properties of a given object.

local object = {a = 1, b = 2, c = 3}
_.pick(object,'a','c') -- => "{a = 1, c = 3}"

omit (obj, ...)

*Aliases: _.drop*.

Omits blacklisted properties of a given object.

local object = {a = 1, b = 2, c = 3}
_.omit(object,'a','c') -- => "{b = 2}"

template (obj, template)

*Aliases: _.defaults*.

Applies a template on an object, preserving existing properties.

local obj = {a = 0}
_.template(obj,{a = 1, b = 2, c = 3}) -- => "{a=0, c=3, b=2}"

isEqual (objA, objB, useMt)

*Aliases: _.compare*.

Compares objects:

_.isEqual(1,1) -- => true
_.isEqual(true,false) -- => false
_.isEqual(3.14,math.pi) -- => false
_.isEqual({3,4,5},{3,4,{5}}) -- => false

result (obj, method, ...)

Calls an object method, passing it as a first argument the object itself.

_.result('abc','len') -- => 3
_.result({'a','b','c'},table.concat) -- => 'abc'

isTable (t)

Is the given argument an object (i.e a table) ?

_.isTable({}) -- => true
_.isTable(math) -- => true
_.isTable(string) -- => true

isCallable (obj)

Is the given argument callable ?

_.isCallable(print) -- => true
_.isCallable(function() end) -- => true
_.isCallable(setmetatable({},{__index = string}).upper) -- => true
_.isCallable(setmetatable({},{__call = function() return end})) -- => true

isArray (obj)

Is the given argument an array (i.e. a sequence) ?

_.isArray({}) -- => true
_.isArray({1,2,3}) -- => true
_.isArray({'a','b','c'}) -- => true

isIterable (obj)

Checks if the given object is iterable with pairs .

_.isIterable({}) -- => true
_.isIterable(function() end) -- => false
_.isIterable(false) -- => false
_.isIterable(1) -- => false

isEmpty (obj)

Is the given argument empty ?

_.isEmpty('') -- => true
_.isEmpty({})  -- => true
_.isEmpty({'a','b','c'}) -- => false

isString (obj)

Is the given argument a string ?

_.isString('') -- => true
_.isString('Hello') -- => false
_.isString({}) -- => false

isFunction (obj)

Is the given argument a function ?

_.isFunction(print) -- => true
_.isFunction(function() end) -- => true
_.isFunction({}) -- => false

isNil (obj)

Is the given argument nil ?

_.isNil(nil) -- => true
_.isNil() -- => true
_.isNil({}) -- => false

isNumber (obj)

Is the given argument a number ?

_.isNumber(math.pi) -- => true
_.isNumber(math.huge) -- => true
_.isNumber(0/0) -- => true
_.isNumber() -- => false

isNaN (obj)

Is the given argument NaN ?

_.isNaN(1) -- => false
_.isNaN(0/0) -- => true

isFinite (obj)

Is the given argument a finite number ?

_.isFinite(99e99) -- => true
_.isFinite(math.pi) -- => true
_.isFinite(math.huge) -- => false
_.isFinite(1/0) -- => false
_.isFinite(0/0) -- => false

isBoolean (obj)

Is the given argument a boolean ?

_.isBoolean(true) -- => true
_.isBoolean(false) -- => true
_.isBoolean(1==1) -- => true
_.isBoolean(print) -- => false

isInteger (obj)

Is the given argument an integer ?

_.isInteger(math.pi) -- => false
_.isInteger(1) -- => true
_.isInteger(-1) -- => true

[⬆]

Chaining

Method chaining (also known as name parameter idiom), is a technique for invoking consecutively method calls in object-oriented style. Each method returns an object, and methods calls are chained together. Moses offers chaining for your perusal.
Let's use chaining to get the count of evey single word in some lyrics (case won't matter here).

local lyrics = {
  "I am a lumberjack and I am okay",
  "I sleep all night and I work all day",
  "He is a lumberjack and he is okay",
  "He sleeps all night and he works all day"
}

local stats = _.chain(lyrics)
  :map(function(k,line)
    local t = {}
    for w in line:gmatch('(%w+)') do
      t[#t+1] = w
    end
    return t
  end)
  :flatten()
  :countBy(function(i,v) return v:lower() end)
  :value()

-- => "{
-- =>    sleep = 1, night = 2, works = 1, am = 2, is = 2,
-- =>    he = 2, and = 4, I = 4, he = 2, day = 2, a = 2,
-- =>    work = 1, all = 4, okay = 2
-- =>  }"

For convenience, you can also use _(value) to start chaining methods, instead of _.chain(value).

Note that one can use :value() to unwrap a chained object.

local t = {1,2,3}
print(_(t):value() == t) -- => true

[⬆]

Import

All library functions can be imported in a context using import into a specified context.

local context = {}
_.import(context)

context.each({1,2,3},print)

-- => 1 1
-- => 2 2
-- => 3 3

When no context was provided, it defaults to the global environment _G.

_.import()

each({1,2,3},print)

-- => 1 1
-- => 2 2
-- => 3 3

Passing noConflict argument leaves untouched conflicting keys while importing into the context.

local context = {each = 1}
_.import(context, true)

print(context.each) -- => 1
context.eachi({1,2,3},print)

-- => 1 1
-- => 2 2
-- => 3 3

[⬆]

Moses

Contents

Topics

Modules

Topic tutorial.md

each (t, f, ...)

eachi (t, f, ...)

at (t, ...)

count (t, value)

countf (t, f, ...)

cycle (t, n)

map (t, f, ...)

reduce (t, f, state)

reduceRight (t, f, state)

mapReduce (t, f, state)

mapReduceRight (t, f, state)

include (t, value)

detect (t, value)

contains (t, value)

findWhere (t, props)

select (t, f, ...)

reject (t, f, ...)

all (t, f, ...)

invoke (t, method, ...)

pluck (t, property)

max (t, transform, ...)

min (t, transform, ...)

shuffle (t, seed)

same (a, b)

sort (t, comp)

groupBy (t, iter, ...)

countBy (t, iter, ...)

size (...)

containsKeys (t, other)

sameKeys (tA, tB)

toArray (...)

find (array, value, from)

reverse (array)

selectWhile (array, f, ...

dropWhile (array, f, ...

sortedIndex (array, value, comp, sort)

indexOf (array, value)

lastIndexOf (array, value)

addTop (array, ...)

push (array, ...)

pop (array, n)

unshift (array, n)

pull (array, ...)

removeRange (array, start, finish)

chunk (array, f, ...)

slice (array, start, finish)

first (array, n)

initial (array, n)

last (array, n)

rest (array, index)

compact (array)

flatten (array, shallow)

difference (array, array2)

union (...)

intersection (array, ...)

symmetricDifference (array, array2)

unique (array)

isunique (array)

zip (...)

append (array, other)

interleave (...)

interpose (value, array)

range (...)

rep (value, n)

partition (array, n)

permutation (array)

invert (array)

concat (array, sep, i, j)

identity (value)

once (f)

memoize (f, hash)

after (f, count)

compose (...)

pipe (value, ...)

complement (f)

Topic `tutorial.md`