Filtering

Operations that output a subset of their input items.

Drop

Drop<type>(n)
Drop(n)

Output all input items except the first n

Take

Take<type>(n)
Take(n)

Output only the first n input items.

Dedup

Dedup<type>()
Dedup()

Output every input item that is not equal to the previous input item.

Dedup (expiring)

Dedup<type>()
Dedup()

Output the input item if it is not equal to the previous input or it has been more than milli milliseconds since the last output.

Debounce

Debounce<type>(millis)
Debounce(millis)

Outputs each input after millis milliseconds if no other input has been received.

Throttle

Throttle<type>(millis)
Throttle(millis)

Rate limits the input stream to average at most one value per millis milliseconds. It functions by outputing the first input received (if any) in successive windows of millis milliseconds.

Sample

Sample<type>(millis)
Sample(millis)

Generates a stream of values with the latest value from its input stream every millis milliseconds.

Over

Over<type>(threshold)
Over(threshold)

Output only input items greater than threshold.

Under

Under<type>(threshold)
Under(threshold)

Output only input items less than threshold.

AtLeast

AtLeast<type>(threshold)
AtLeast(threshold)

Output only input items greater than or equal to threshold.

AtMost

AtMost<type>(threshold)
AtMost(threshold)

Output only input items less than or equal to threshold.

Positive

Positive<type>()
Positive()

Output only input items that are greater than 0.

Negative

Negative<type>()
Negative()

Output only input items that are less than 0.

Zero

Zero<type>()
Zero()

Output only input items that are less than 0.

True

True<type>()
True()

Output only input items equal to true.

False

False<type>()
False()

Output only input items equal to false.

Filter

Filter<type>(function)
Filter(function)

For each input item, apply the given function and output the input if the function returns true.

Transformation

Operations that transforms each input item to produce an output item.

Const

Const<in-type,out-type>(value)
Const(value)

For each input item, output value.

Abs

Abs<type>()
Abs()

For each input item, output it's absolute value.

Scale

Scale<type>(k)
Scale(k)

For each input item, output k × input value.

Add

Add<type>(b)
Add(b)

For each input item, output b + input value.

Clamp

Clamp<type>(lo, hi)
Clamp(lo, hi)

For each input item, output lo if the input is less than lo, hi if the input more than hi, or the input value if it is between lo and hi.

ClampLow

ClampLow<type>(lo)
ClampLow(lo)

For each input item, output the maximum of the input value or lo.

ClampHigh

ClampHigh<type>(hi)
ClampHigh(hi)

For each input item, output the minimum of the input value or hi.

IsOver

IsOver<type>(threshold)
IsOver(threshold)

Output true for each input item greater than threshold otherwise false.

IsUnder

IsUnder<type>(threshold)
IsUnder(threshold)

Output true for each input item less than threshold otherwise false.

IsAtLeast

IsAtLeast<type>(threshold)
IsAtLeast(threshold)

Output true for each input item greater than or equal to threshold otherwise false.

IsAtMost

IsAtMost<type>(threshold)
IsAtMost(threshold)

Output true for each input item less than or equal to threshold otherwise false.

IsPositive

IsPositive<type>()
IsPositive()

Output true for each input item that is greater than 0 otherwise false.

IsNegative

IsNegative<type>()
IsNegative()

Output true for each input item that is less than 0 otherwise false.

IsZero

IsZero<type>()
IsZero()

Output true for each input item that is less than 0 otherwise false.

Toggle

Toggle<in-type,out-type>(initial)
Toggle(initial)

On the first input, output ! initial and thereafter output ! previous output.

Project1

Project1<type>()
Project1()

For each tuple input item, output the 1st element of the tuple

Project2

Project2<type>()
Project2()

For each tuple input item, output the 2nd element of the tuple

Project3

Project3<type>()
Project3()

For each tuple input item, output the 3rd element of the tuple

Counted

Counted<in-type,counter-type>()
Counted()

For each tuple input item, output a tuple with the input item and total number of inputs seen.

Map

Map<in-type,out-type>(function)
Map(function)

For each tuple input item, apply the given function to the input and output the returned value.

The signature of function is

out-type function(const in-type&)

Map (no copy)

Map<in-type,out-type>(function)
N/A

For each tuple input item, call the given function with the input and result and output the result.

The signature of function is

void function(const in-type&, out-type&)

Scan

Scan<in-type,state-type>(function, init)
Scan(function, init)

The scan operator keeps a state of state-type which is initially init. For each input item, the given function is called with the input item and the current state as arguments. The returned value is output and becomes the new state.

The function signature of the update function is

state-type update(const in-type&, const state-type&)

Scan (no copy)

Scan<in-type,state-type>(update, init)
N/A

The scan operator keeps a state of state-type which is initialized by init function (optional). For each input item, the given update function is called with the input item and the current state as arguments. The update can modify the state argument and the new state is the output of the operator.

The function signature of the update function is

void update(const in-type&, state-type&)

and the function signature of the init funciton is

void init(state-type&)

Aggregation

Operators that aggregate or summarize information from multiple items in output items.

Count

Count<type>()
Count()

For each item received, output the total number of items received since the start.

WinSum

WinSum<type,width>()
WinSum(width)

Outputs the sum of a width size sliding window over the input stream.

SumOf

SumOf<type,count>()
SumOf(count)

Outputs the sum of each batch of count input items.

SumOver

SumOver<type>(millis)
SumOver(millis)

Outputs the sum of each batch of input items received over millis milliseconds.

WinAverage

WinAverage<type,width>()
WinAverage(width)

Outputs the average of a width size sliding window over the input stream.

AverageOf

AverageOf<type,count>()
AverageOf(count)

Outputs the average of each batch of count input items.

AverageOver

AverageOver<type>(millis)
AverageOver(millis)

Outputs the average of each batch of input items received over millis milliseconds.

WinMin

WinMin<type,width>()
WinMin(width)

Outputs the minimum of a width size sliding window over the input stream.

MinOf

MinOf<type,count>()
MinOf(count)

Outputs the minimum of each batch of count input items.

MinOver

MinOver<type>(millis)
MinOver(millis)

Outputs the minimum of each batch of input items received over millis milliseconds.

WinMax

WinMax<type,width>()
WinMax(width)

Outputs the maximum of a width size sliding window over the input stream.

MaxOf

MaxOf<type,count>()
MaxOf(count)

Outputs the maximum of each batch of count input items.

MaxOver

MaxOver<type>(millis)
MaxOver(millis)

Outputs the maximum of each batch of input items received over millis milliseconds.

String operators

Lines

Lines()
N/A

Output a stream of lines (strbuf class) from an input stream of characters (char).

Format

Format<type>(format)
N/A

Build a formatted string from input items using the format template. Any occurrence of $1 in the template is replaced by the input value. Occurrences of $t are replaced by the current time as a Unix timestamp (number of seconds since Jan. 1, 1970).

Split

Split<max-fields>(delimiter)
Split()

Splits each input string at the given delimiter and outputs the resulting strings in a vector. The C++ types are strbuf input and Vec<strbuf,max-fields> output.

ToString

ToString<input-type>()
ToString()

Converts the input values to a string and outputs it as a strbuf

ToJson

ToJson<input-type>()
ToJson()

Converts the input values to a JSON string and outputs it as a jsons

Miscellaneous

Iterate

Iterate<type>(millis, repeat)
Iterate(millis, repeat)

Generates a stream of values from a generator (e.g. Range). The values are generated one every millis milliseconds. If repeat is true then the iterater will start over with the 1st value after it reaches the last. The millis and repeat parameters are optional with defaults 0 and false respectively.

Poll

Poll<type>(millis)
Poll(millis)

Generates a stream of values from an input by polling the current value every millis milliseconds.

Build

Build<in-type,state-type,result-type>(function, init)
N/A

This operator replaces the scan -> filter -> map pattern with a single operator and also only allocates one result object at creation time. The operator keeps a state of state-type which is initially init. For each input item, the given function is called with the input item and the current state and result as reference arguments. If the function returns true, the current value of result is output otherwise nothing is output.