return5/Lua8Streams

simple module i made in an attempt to emulate java 8 streams.

Streams

a simple module for emulating java 8 streams in lua.
Doesn't provide 100% of functionality of native java streams.

Please see 'examples.lua' for commented and working examples.

Functions

• Streams:stream(t)
  • creates a new stream from a table.

Intermediate operations

• Streams:map(func)

  • intermediate operator which maps inputs into different outputs.
  • takes in a function which does the mapping.

• Streams:filter(func)

  • intermediate operator which filters input items.
  • takes in a function which accepts inputs and returns a boolean value.

• Streams:skip(n)

  • intermediate function which returns a stream skipping over the first n items.
  • if used, it should be the first intermediate method called.

• Streams:limit(n)

  • intermediate operation which returns a stream limited to the first n items.
  • if used, it should be the first intermediate method called.

Finalizer methods

• Streams:collect()

  • finalizer method which returns a table with each item as an index of that table.

• Streams:distinct()

  • finalizer method which returns a table which has all duplicate values removed.

• Streams:join(del,prefix,suffix)

  • finalizer method which converts stream into string.
  • all parameters are optional. takes in delimeter value for each item, a prefix for each item, and a postfix for each item.

• Streams:partitionBy(func)

  • finalizer method which returns a table with keys "true" and "false", with values which are tables containing each item from the stream which evaluates to either true false in the provided function.
  • takes in a function which should accept the current item and the index value, should return a boolean value.

• Streams:groupBy(keyFunc,valueFunc)

  • finalizer method which returns a table where the keys and values are generated from the provided functions.
  • keyFunc generates the keys. should take in item and index value. should return key value.
  • valueFunc generated the values. should take in key, item, the table to return, and the index value. no return is expected.

• Streams:average(func)

  • finalizer method which returns the average of items in stream.
  • optional parameter is a function for summing items in stream.

• Streams:sum(func)

  • finalizer method which returns the sum of all items in the stream.
  • optional parameter is a function which controls how items are summed.

• Streams:count()

  • finalizer method which returns the count of items in teh stream.

• Streams:reduce(func,ident)

  • finalizer method which reduces stream down to a single value.
  • func is a function which takes in current item and the results so far of reduction. returns updated result.
  • ident is optional. inital value for starting reduction, if not provided then first item in stream is used.

• Streams:forEach(func)

  • for each item in the stream call the given function.
  • func should take in the item and return nothing.

• Streams:allMatch(matchingFunc)

  • finalizer method which returns true if all items in stream evaluates to true in given function. otherwise, returns false.
  • matchingFunc should take in item and index of item, should return true or false.

• Streams:anyMatch(matchingFunc)

  • finalizer which returns true is any item in stream evaluates to true in the given function. otherwise, return false.
  • matchingFunc should accept item and index of item. should return true or false.

• Streams:noneMatch(matchingFunc)

  • finalizer method which returns true if none of the items in stream evaluates to true in the provided function. otherwise, returns false.
  • matchingFunc should accept item and index, returns true or false.

• Streams:findFirst()

  • finalizer which returns the first item in the stream.

• Streams:max(cmp)

  • finalizer method which returns the max value in the steam.
  • accepts optional compare function which handles comparison for max value.

• Streams:min(cmp)

  • finalizer method which returns the min value in the steam.
  • accepts optional compare function which handles comparison for min value.

Basic working example

    --import the module
    local Streams = require("Streams')
    --create a stream, filter it, then collect the reuslts.
    --first create a stream from the given table.
    --we then filter out non even indexes.
    --then we collect the results into a table.
    local results = Streams({1,2,3,4,5,6,7,8}):filter(function(_,i) return i % 2 == 0 end):collect()    
    
    --from this point do whatever you want with the table.