sequences

About

sequences is a collection of utilities for working with lazily-evaluated sequences of data.

Working with lazily-evaluated sequences can be more efficient than other JS alternatives, as it allows you to minimize intermediate memory allocations where possible, and only perform operations on elements that contribute to your final result.

 
// temporary arrays are created by filter and map,
let val = [-3, -2, -1, 0, 1, 2, 3]
    .filter((val) => val > 0)
    .map((val) => val + 1)
    .reduce((sum, val) => sum + val, 0);
 
// no temporary arrays
let val2 = FromArray([-3, -2, -1, 0, 1, 2, 3])
    .pipe(Filter, (val) => val > 0)
    .pipe(Map, (val) => val + 1)
    .pipe(Reduce, (sum, val) => sum + val, 0)
    .read();
 

Why not ES6 Iterators?

• ES6 Iterators require a temporary { done, value } object to be allocated with every call, which reduces performace.

• Sequence().read() accepts a 'recycle' parameter when called, which allows you to re-use previously allocated values, to minimize allocations.

• Sequence().read() returns the next result or the terminator Sequence().END, which can simplify control flow compared to having an "independent" control channel (the iterator done parameter).

Why ES6 Iterators?

• You want to use the Iterable protocol.

API

sequences : object

Kind: global namespace

• sequences : object
  • .Sequence
    • new Sequence()
    • sequence.read(recycle)
    • sequence.pipe(sequenceConstructor, ...args)
  • .Assert ⇒ Sequence
  • .Concat ⇒ Sequence
  • .Count ⇒ Sequence
  • .Deduplicate ⇒ Sequence
  • .Default ⇒ Sequence
  • .Drain ⇒ Sequence
  • .Each ⇒ Sequence
  • .Filter ⇒ Sequence
  • .Flatten ⇒ Sequence
  • .FromArray ⇒ Sequence
  • .FromBlocks ⇒ Sequence
  • .FromIterator ⇒ Sequence
  • .From ⇒ Sequence
  • .FromObject ⇒ Sequence
  • .FromSet ⇒ Sequence
  • .Group ⇒ Sequence
  • .Join ⇒ Array
  • .Map ⇒ Sequence
  • .Reduce ⇒ Sequence
  • .Replace ⇒ Sequence
  • .Slice ⇒ Sequence
  • .Sort ⇒ Sequence
  • .Splice ⇒ Sequence
  • .ToArray ⇒ Sequence
  • .ToBlocks ⇒ Sequence
  • .ToIterator ⇒ Iterator
  • .ToObject ⇒ Sequence
  • .ToSet ⇒ Sequence
  • .Window ⇒ Sequence
  • .Zip
  • .bytes : object
    • .FromHex ⇒ Sequence
    • .FromWords ⇒ Sequence
    • .ToHex ⇒ Sequence
    • .ToWords ⇒ Sequence
  • .random : object
    • .RandomBoolean ⇒ Sequence
    • .RandomInteger ⇒ Sequence
    • .Random ⇒ Sequence
    • .RandomSelection ⇒ Sequence
    • .XORShift32 ⇒ Sequence

---

sequences.Sequence

Kind: static class of sequences

• .Sequence
  • new Sequence()
  • sequence.read(recycle)
  • sequence.pipe(sequenceConstructor, ...args)

---

new Sequence()

Sequence is the base sequence class. it should always be subclassed. sequence constructors should never require new.

---

sequence.read(recycle)

read is the core method of a sequence. read should return the next value in the sequence. if there are no more values to read, read should return Sequence.END

Kind: instance method of Sequence
Params

• recycle - a 'container' value to re-use when returning the next value. always optional.

---

sequence.pipe(sequenceConstructor, ...args)

// this
let seq = From(1, 2, 3, 4);
seq = Slice(seq, 0, 10);
seq = Assert(seq, (val, i) => Number.isInteger(val));
seq = ToArray(seq);
 
// is equivalent to this
const seq = From(1, 2, 3, 4)
   .pipe(Slice, 0, 10)
   .pipe(Assert, (val, i) => Number.isInteger(val))
   .pipe(ToArray);

pipe is a utility method to wrap one sequence in another.

Kind: instance method of Sequence
Params

• sequenceConstructor - the constructor function for another sequence. pipe assumes the constructor takes a source sequence as its first argument
• ...args * - any number of additional args to pass into sequenceConstructor

---

sequences.Assert ⇒ Sequence

 
let Assert = require('sequences/Assert');
let From = require('sequences/From');
let ToArray = require('sequences/ToArray');
 
let isInteger = (val) => Number.isInteger(val);
 
// val is [ 1, 2, 3, 4 ]
let val = From(1, 2, 3, 4)
  .pipe(Assert, isInteger)
  .pipe(ToArray)
  .read();
 
// throws an assertion error
let val2 = From(1, 2, 3, "4")
  .pipe(Assert, isInteger)
  .pipe(ToArray)
  .read();
 

Assert is a sequence wrapper that builds a sequence to run an assertion against every value in the sequence

Kind: static property of sequences
Params

• source Sequence - a source sequence
• assert function - an assertion function
• error function - an error builder function

---

sequences.Concat ⇒ Sequence

 let Count = require('sequences/Count');
 let Slice = require('sequences/Slice');
 let Concat = require('sequences/Concat');
 
 // res is '0 - 1 - 2 - 3 - 4':
 let res = Count()
   .pipe(Slice, 0, 5)
   .pipe(Concat, ' - ')
   .read();

Concat performs string concatenation of all elements in a sequence

Kind: static property of sequences
Params

• source Sequence - a source sequence
• separator string - an optional separator string, to be placed in

---

sequences.Count ⇒ Sequence

 
let Count = require('sequences/Count');
let Slice = require('sequences/Slice');
let ToArray = require('sequences/ToArray');
 
// val is [ 0, 1, 2, 3 ]
let val = Count()
  .pipe(Slice, 0, 4)
  .pipe(ToArray)
  .read();
 

Count is a sequence constructor that builds a sequence that counts integers upward Count never terminates, so make sure to add a terminating sequence like a Slice somewhere after it.

Kind: static property of sequences
Params

• start number - the number to start counting from

---

sequences.Deduplicate ⇒ Sequence

 let Count = require('sequences/Count');
 let Deduplicate = require('sequences/Deduplicate');
 let Map = require('sequences/Map');
 let Slice = require('sequences/Slice');
 let ToArray = require('sequences/ToArray');
 
 // res is [0, 1, 2, 3]:
 let res = Count()
   .pipe(Slice, 0, 50)
   .pipe(Map, (val) => val % 4)
   .pipe(Deduplicate)
   .pipe(ToArray)
   .read();

Deduplicate removes duplicates from a sequence, while maintaining sequence order NOTE: Deduplicate uses a Set to track already-seen elements, so it can potentially use a large amount of memory

Kind: static property of sequences
Params

• source Sequence - a source sequence
• projection function - an optional projection function, that you can use to deduplicate based off some part of values

---

sequences.Default ⇒ Sequence

 let Count = require('sequences/Count');
 let Default = require('sequences/Default');
 let Filter = require('sequences/Filter');
 let Slice = require('sequences/Slice');
 
 // res is [0, 10, 20, 30, 40]:
 let res = Count()
   .pipe(Slice, 0, 50)
   // filter out everything, so the sequence returns END
   .pipe(Filter, (val) => val > 9999)
   .pipe(Default, 0)
   .read(); // returns 0

Default provides a default return value to the sequence, if the sequence terminates without returning any value

Kind: static property of sequences
Params

• source Sequence - a source sequence
• _default function - the default value

---

sequences.Drain ⇒ Sequence

 let Count = require('sequences/Count');
 let Drain = require('sequences/Drain');
 let Slice = require('sequences/Slice');
 
 // returns sequence terminator
 Count()
   .pipe(Slice, 0, 4)
   .pipe(Drain)
   .read();

Drain is a sequence constructor wraps a source sequence, and when read is called it reads the entire sequence and throws it away. Useful for sequences with side-effects.

Kind: static property of sequences
Params

• source Sequence - the source sequence to drain

---

sequences.Each ⇒ Sequence

 let Count = require('sequences/Count');
 let Drain = require('sequences/Drain');
 let Each = require('sequences/Each');
 let Slice = require('sequences/Slice');
 
 // should log:
 // element 0 is 1
 // element 1 is 2
 // element 2 is 3
 Count()
   .pipe(Slice, 1, 4)
   .pipe(Each, (val, i) => console.log(`element ${i} is ${val}`))
   .pipe(Drain)
   .read();

Each takes a function, and called it once per every element in a sequence. Useful for logging, or performing other side-effects.

Kind: static property of sequences
Params

• source Sequence - the source sequence to drain
• each function - a function to get called for each value

---

sequences.Filter ⇒ Sequence

 let Count = require('sequences/Count');
 let Filter = require('sequences/Filter');
 let Slice = require('sequences/Slice');
 let ToArray = require('sequences/ToArray');
 
 // res is [0, 10, 20, 30, 40]:
 let res = Count()
   .pipe(Slice, 0, 50)
   .pipe(Filter, (val, i) => (val % 10 === 0))
   .pipe(ToArray)
   .read();

Filter removes some items from a sequence.

Kind: static property of sequences
Params

• source Sequence - a source sequence
• filter function - a filter function

---

sequences.Flatten ⇒ Sequence

 let From = require('sequences/From');
 let Flatten = require('sequences/Flatten');
 let ToArray = require('sequences/ToArray');
 
 // res is [1, 2, 3, 4, 5, 6]:
 let res = From(1, [], [2, 3], From(4, 5, 6))
   .pipe(Flatten)
   .pipe(ToArray)
   .read();

Flatten 'flattens' a sequence of "collections" into a sequence of elements. right now, Flatten supports flattening sequences and array-like objects. Anything else will be passed through without modification.

Kind: static property of sequences
Params

• source Sequence - a sequence of arrays

---

sequences.FromArray ⇒ Sequence

 let FromArray = require('sequences/FromArray');
 let ToArray = require('sequences/ToArray');
 
 // res is [1, 2, 3]:
 let res = FromArray([ 1, 2, 3 ])
   .pipe(ToArray)
   .read();

FromArray builds a sequence from an array.

Kind: static property of sequences
Params

• values array - values to return in the sequence, in order

---

sequences.FromBlocks ⇒ Sequence

 let From = require('sequences/From');
 let FromBlocks = require('sequences/FromBlocks');
 let ToArray = require('sequences/ToArray');
 
 // res is [1, 2, 3, 4, 5, 6]:
 let res = From([ 1, 2, 3 ], [4, 5, 6])
   .pipe(FromBlocks)
   .pipe(ToArray)
   .read();

FromBlocks 'flattens' a sequence of arrays into a sequence of elements. FromBlocks is a legacy alias for Flatten

Kind: static property of sequences
Params

• source Sequence - a sequence of arrays

---

sequences.FromIterator ⇒ Sequence

FromIterator builds a sequence from an iterator

Kind: static property of sequences
Params

• iterator Iterator - iterator to convert into a sequence

---

sequences.From ⇒ Sequence

 let From = require('sequences/From');
 let ToArray = require('sequences/ToArray');
 
 // res is [1, 2, 3]:
 let res = From(1, 2, 3)
   .pipe(ToArray)
   .read();

From builds a sequence from its arguments.

Kind: static property of sequences
Params

• ...values * - values to return in the sequence, in order

---

sequences.FromObject ⇒ Sequence

 let FromObject = require('sequences/FromObject');
 let ToArray = require('sequences/ToArray');
 
 // res is [{ key: 'a', value: 1 }, { key: 'b', value: 2 }]:
 let res = FromObject({ a: 1, b: 2 })
   .pipe(ToArray)
   .read();

FromObject builds a sequence of key-value pairs from an object.

Kind: static property of sequences
Params

• obj object - object from which to return a sequence of key-value pairs

---

sequences.FromSet ⇒ Sequence

FromSet builds a sequence from a Set

Kind: static property of sequences
Params

• set Set - set to convert into a sequence

---

sequences.Group ⇒ Sequence

 let From = require('sequences/From');
 let Group = require('sequences/Group');
 let ToArray = require('sequences/ToArray');
 
 // res is [ [1, 2, 3], [4, 5, 6] ]:
 let res = From(1, 2, 3, 4, 5, 6)
   .pipe(Group, 3)
   .pipe(ToArray)
   .read();

Group converts a sequence into a sequence of 'blocks' (fixed-size arrays of the elements)

Kind: static property of sequences
Params

• source Sequence - the source sequence
• size number - the size of blocks to emit

---

sequences.Join ⇒ Array

 let Join = require('sequences/Join');
 let ToArray = require('sequences/ToArray');
 
 // res is [ [1, 4], [1, 5], [1, 6], [2, 4], [2, 5], [2, 6], [3, 4], [3, 5], [3, 6] ]:
 let res = Join([1, 2, 3], [4, 5, 6])
   .pipe(ToArray)
   .read();

Join converts two arrays into a number (first array size * second array size) of pairs (arrays of two items)

Kind: static property of sequences
Params

• outerSource Array - first array
• innerSource Array - second array

---

sequences.Map ⇒ Sequence

 let Count = require('sequences/Count');
 let Map = require('sequences/Map');
 let Slice = require('sequences/Slice');
 let ToArray = require('sequences/ToArray');
 
 // res is [1, 2, 3]:
 let res = Count()
   .pipe(Slice, 0, 4)
   .pipe(Map, (val, i) => val + 1)
   .pipe(ToArray)
   .read();

Map transforms each element in a sequence.

Kind: static property of sequences
Params

• source Sequence - a source sequence
• map function - a map function

---

sequences.Reduce ⇒ Sequence

 let Count = require('sequences/Count');
 let Reduce = require('sequences/Reduce');
 let Slice = require('sequences/Slice');
 
 // res is 6:
 let res = Count()
   .pipe(Slice, 0, 4)
   .pipe(Reduce, (state, val, i) => state + val)
   .read();

Reduce 'reduces' a sequence of elements to a single result.

Kind: static property of sequences
Params

• source Sequence - a source sequence
• reduce function - a reduce function
• state * - the initial value of the state

---

sequences.Replace ⇒ Sequence

 let From = require('sequences/From');
 let Replace = require('sequences/Replace');
 let ToArray = require('sequences/ToArray');
 
 // res is [1, 1, 2, 2, 3, 3]:
 let res = From(1, -1, 2, -2, 3, -3)
   .pipe(Replace, (val) => val < 0, (val) => -val)
   .pipe(ToArray)
   .read();

Replace allows you to replace some elements in a sequence dynamically. It acts like a mapping with a pre-selector choosing which elements to map

Kind: static property of sequences
Params

• source Sequence - a source sequence
• selector function - the selector function, that chooses which elements to replace
• mapper function - the mapper function, that replaces the elements

---

sequences.Slice ⇒ Sequence

 let Count = require('sequences/Count');
 let Slice = require('sequences/Slice');
 let ToArray = require('sequences/ToArray');
 
 // res is [1, 2, 3]:
 let res = Count()
   .pipe(Slice, 0, 4)
   .pipe(ToArray)
   .read();

Slice 'slices' out a piece of a sequence to use

Kind: static property of sequences
Params

• source Sequence - a source sequence
• start integer - the index to start from (inclusive)
• end integer - the index to end at (exclusive)

---

sequences.Sort ⇒ Sequence

 let From = require('sequences/From');
 let Sort = require('sequences/Sort');
 let ToArray = require('sequences/ToArray');
 
 // res is [1, 2, 3]:
 let res = From(3, 2, 1)
   .pipe(Sort)
   .pipe(ToArray)
   .read();

Sort sorts a sequence inline.

NOTE: Sort must buffer all values in the sequence for sorting, so it has a space complexity of O(N)

Kind: static property of sequences
Params

• source Sequence - the source sequence

---

sequences.Splice ⇒ Sequence

 let From = require('sequences/From');
 let Splice = require('sequences/Splice');
 let ToArray = require('sequences/ToArray');
 
 // res is [1, 2, 3, 4, 5, 6]:
 let res = Splice(From(1, 2, 3), From(4, 5, 6))
   .pipe(ToArray)
   .read();

Splice 'splices' several sequences together, concatenating them into a single sequence

Kind: static property of sequences
Params

• ...sources Sequence - the source sequences

---

sequences.ToArray ⇒ Sequence

 let From = require('sequences/From');
 let ToArray = require('sequences/ToArray');
 
 // res is [1, 2, 3]:
 let res = From(1, 2, 3)
   .pipe(ToArray)
   .read();

ToArray converts a sequence into an array.

NOTE: ToArray will always return exactly once. If the source sequence is empty, ToArray will return an empty array.

Kind: static property of sequences
Params

• source Sequence - the source sequence

---

sequences.ToBlocks ⇒ Sequence

 let From = require('sequences/From');
 let ToBlocks = require('sequences/ToBlocks');
 let ToArray = require('sequences/ToArray');
 
 // res is [ [1, 2, 3], [4, 5, 6] ]:
 let res = From(1, 2, 3, 4, 5, 6)
   .pipe(ToBlocks, 3)
   .pipe(ToArray)
   .read();

ToBlocks converts a sequence into a sequence of 'blocks' (fixed-size arrays of the elements) ToBlocks is a legacy alias for Group

Kind: static property of sequences
Params

• source Sequence - the source sequence
• size number - the size of blocks to emit

---

sequences.ToIterator ⇒ Iterator

 let From = require('sequences/From');
 let Map = require('sequences/Map');
 let ToIterator = require('sequences/ToIterator');
 
 // res is [1, 2, 3]:
 let res = From(1, 2, 3)
   .pipe(Map, (x) => x + 1)
   .pipe(ToIterator);
 
 console.log(res.next()); // { value: 2, done: false }
 

ToIterator converts a sequence into an iterator, if you need one

Kind: static property of sequences
Params

• source Sequence - the source sequence

---

sequences.ToObject ⇒ Sequence

 let From = require('sequences/From');
 let ToObject = require('sequences/ToObject');
 
 // res is { a: 1, b: 2 }:
 let res = From({ key: 'a', value: 1 }, { key: 'b', value: 2 })
   .pipe(ToObject)
   .read();

ToObject converts a sequence into an object The sequence must be a sequence of key-value pairs, structured as an object with a 'key' and a 'value' property.

NOTE: ToObject will always return exactly once. If the source sequence is empty, ToObject will return an empty object.

Kind: static property of sequences
Params

• source Sequence - the source sequence

---

sequences.ToSet ⇒ Sequence

ToSet converts a sequence into a Set

NOTE: ToSet will always return exactly once. If the source sequence is empty, ToSet will return an empty Set.

Kind: static property of sequences
Params

• source Sequence - the source sequence

---

sequences.Window ⇒ Sequence

 
let From = require('sequences/From');
let ToArray = require('sequences/ToArray');
let Window = require('sequences/Window');
 
let isInteger = (val) => Number.isInteger(val);
 
// val is [ [ 1, 2, 3 ], [ 2, 3, 4 ], [ 3, 4, 5 ] ]
let val = From(1, 2, 3, 4, 5)
  .pipe(Window, 3)
  .pipe(ToArray)
  .read();
 
// val2 is [ [ 1 ], [ 1, 2 ], [ 1, 2, 3 ], [ 2, 3, 4 ], [ 3, 4, 5 ], [ 4, 5 ], [ 5 ] ]
let val2 = From(1, 2, 3, 4, 5)
  .pipe(Window, 3, true)
  .pipe(ToArray)
  .read();
 

Window is a sequence wrapper that returns a fixed-length sliding window of a source sequence

Kind: static property of sequences
Params

• source Sequence - a source sequence
• size number - the size of the window buffer
• edges boolean - allow edges (a not-full buffer)

---

sequences.Zip

 
 let Zip = require('sequences/Zip');
 let From = require('sequences/From');
 let ToArray = require('sequences/ToArray');
 
 
 // res is [ [1, 4], [2, 5], [3, 6] ]:
 let res = Zip([1, 2, 3], [4, 5, 6])
   .pipe(ToArray)
   .read();
 
 
 // Zip takes in sequences or arrays as sources
 // res is [ [1, 4], [2, 5], [3, 6] ]:
 let res = Zip([1, 2, 3], From(4, 5, 6))
   .pipe(ToArray)
   .read();
 
 
 // the zipped sequence will be the length of the _longest_ source
 // if any source sequences end early, their result will be undefined
 // res is [ [1, 4], [2, 5], [undefined, 6] ]:
 let res = Zip([1, 2], [4, 5, 6])
   .pipe(ToArray)
   .read();
 
 
 // if you need to clip your results to the shortest sequence, use Zip.Short
 // res is [ [1, 4], [2, 5] ]:
 let res = Zip.Short([1, 2], [4, 5, 6])
   .pipe(ToArray)
   .read();
 

Zip combines any number of arrays or sequences into a single sequence of tuples of elements at the same index

Kind: static property of sequences

---

sequences.bytes : object

Kind: static namespace of sequences

• .bytes : object
  • .FromHex ⇒ Sequence
  • .FromWords ⇒ Sequence
  • .ToHex ⇒ Sequence
  • .ToWords ⇒ Sequence

---

bytes.FromHex ⇒ Sequence

 
let FromHex = require('sequences/bytes/FromHex');
*

FromHex converts a hex string into a Sequence of bytes

Kind: static property of bytes
Params

• hex string

---

bytes.FromWords ⇒ Sequence

 // res is [1, 2, 3, 4, 5, 6]:
 let res = From([ 1, 2, 3 ], [4, 5, 6])
   .pipe(FromWords)
   .pipe(ToArray)
   .read();

FromWords 'flattens' a sequence of words (32 bit integers) into a sequence of elements.

Kind: static property of bytes
Returns: Sequence - - a sequence of bytes
Params

• source Sequence - a sequence of words
• isLittleEndian boolean - an optional parameter to set the byte order, default true

---

bytes.ToHex ⇒ Sequence

 // res is '000102':
 let res = From(1, 2, 3)
   .pipe(ToHex)
   .read();

ToHex converts a sequence into an array.

NOTE: ToHex will always return exactly once. If the source sequence is empty, ToHex will return an empty string.

Kind: static property of bytes
Params

• source Sequence - the source sequence

---

bytes.ToWords ⇒ Sequence

 // res is [1, 2, 3, 4, 5, 6]:
 let res = From([ 1, 2, 3 ], [4, 5, 6])
   .pipe(ToWords)
   .pipe(ToArray)
   .read();

ToWords 'flattens' a sequence of words (32 bit integers) into a sequence of elements.

Kind: static property of bytes
Returns: Sequence - - a sequence of bytes
Params

• source Sequence - a sequence of words
• isLittleEndian boolean - an optional parameter to set the byte order, default true

---

sequences.random : object

Kind: static namespace of sequences

• .random : object
  • .RandomBoolean ⇒ Sequence
  • .RandomInteger ⇒ Sequence
  • .Random ⇒ Sequence
  • .RandomSelection ⇒ Sequence
  • .XORShift32 ⇒ Sequence

---

random.RandomBoolean ⇒ Sequence

 
let RandomBoolean = require('sequences/random/RandomBoolean');
*

RandomBoolean is a Sequence pseudo-random number generator that returns a random boolean.

Kind: static property of random
Params

• seed number - an optional 32 bit seed

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random.RandomInteger ⇒ Sequence

 
let RandomInteger = require('sequences/random/RandomInteger');
*

RandomInteger is a Sequence pseudo-random number generator that returns a random int between min and max, inclusive. RandomInteger returns in the range [0, 1] by default. RandomInteger has 32 bits of precision.

Kind: static property of random
Params

• min number - the minimum possible integer to return
• max number - the maximum possible integer to return
• seed number - an optional 32 bit seed

---

random.Random ⇒ Sequence

 
let Random = require('sequences/random/Random');
*

Random is a Sequence pseudo-random number generator that returns a random number between min and max, inclusive. Random returns in the range [0, 1] by default. Random has 32 bits of precision.

Kind: static property of random
Params

• min number
• max number
• seed number - an optional 32 bit seed

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random.RandomSelection ⇒ Sequence

 
let RandomSelection = require('sequences/random/RandomSelection');
*

RandomSelection is a Sequence generator that returns a random relection from the choices.

Kind: static property of random
Params

• choices Array - the selection choices
• seed number - an optional 32 bit seed

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random.XORShift32 ⇒ Sequence

 
let XORShift32 = require('sequences/random/XORShift32');
*

XORShift32 is a Sequence implementation of the XORShift32 PRNG algorithm

Kind: static property of random
Params

• seed number - an optional 32 bit seed

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