Operations

Operations are the building blocks of a variable. The body of a variable is a list of operations — each line beginning with a dash — that run one after the other. Each operation takes the result of the previous one as its input, does some work, and passes its output to the next. The result of the last operation becomes the value of the variable.

variables:
  part-count:
    - source: AIN0
    - threshold: 5
    - rising-edge
    - count

See Variables for a walkthrough of this example and the rules governing the first and last operations in a chain.

info

Only three operations can start a chain: source, expression, and state. Every other operation needs an input from the operation before it.

Index

By category

Sources and control flow

Operation	Description
source	Names the data source — pin, register, tag, or another variable — that feeds the chain.
state	Emits a constant value based on a series of expression tests, like an if/else-if/else.
branch	Routes the incoming value through the first matching branch's chain of operations.
if, else-if, else	Keywords used to form the conditions of a branch.
map	Applies a chain of operations to every element of an array.

Expressions and logic

Operation	Description
expression	Applies an expression to the input and outputs the result.
and	Combines the input with an expression result using a logical AND.
or	Combines the input with an expression result using a logical OR.
invert	Inverts a boolean, or negates a number.

Analog conditioning

Operation	Description
threshold	Converts a numeric value to digital high or low at a cutoff.
min	Outputs the smallest of the last N samples, filtering out short rises.
max	Outputs the largest of the last N samples, filtering out short drops.
average	Outputs the average of the last N samples.
min-delta	Holds the last value until the input moves by at least the given amount.
resample	Resamples a stream to a fixed sample rate.
rate-of-change	Outputs the change between samples divided by the time between them.

Digital conditioning

Operation	Description
debounce	Filters out changes shorter than the given window.
on-delay	Switches true only after the input has stayed true for the given time.
off-delay	Switches false only after the input has stayed false for the given time.
toggle	Flips between true and false on each rising edge.
latch-value	Holds a value until a reset expression evaluates true.
ignore-value	Drops values matching a test, repeating the last value that passed.

Event detection

Operation	Description
edge	Emits an event pulse on any transition, in either direction.
rising-edge	Emits an event pulse on each low-to-high transition.
falling-edge	Emits an event pulse on each high-to-low transition.
value-change	Emits an event pulse each time the value changes.
value-increase	Emits an event pulse each time the value increases.
value-decrease	Emits an event pulse each time the value decreases.
value-increase-diff	Emits the size of each increase, then returns to zero.

Counting

Operation	Description
count	Increments by one for each event received.
window-count	Counts the events seen within a trailing time window.
accumulate	Maintains and outputs a running sum of incoming values.

Text and patterns

Operation	Description
pattern-match	Captures the part of a string matching a pattern.
pattern-replace	Replaces the part of a string matching a pattern.
pattern-test	Outputs true when a pattern is present in the string.
pattern-escape	Escapes a value so it can be embedded safely in a pattern.
trim	Removes whitespace and non-printable characters from both ends of a string.
max-length	Truncates a string to a number of characters, or an array to a number of elements.
hash	Applies an md5 or sha1 hash to the input.

Objects, arrays and buffers

Operation	Description
object-keys	Emits an array of an object's keys, or of an array's indexes.
object-values	Emits an array of an object's values.
reject	Removes elements matching a test from an array.
to-buffer	Converts a value into a binary buffer.
from-buffer	Reads a typed value out of a binary buffer at a given offset.

Special values

Operation	Description
when-unavailable	Substitutes a value when the input is UNAVAILABLE.

Alphabetical

Operation	Description
accumulate	Maintains and outputs a running sum of incoming values.
and	Combines the input with an expression result using a logical AND.
average	Outputs the average of the last N samples.
branch	Routes the incoming value through the first matching branch's chain of operations.
count	Increments by one for each event received.
debounce	Filters out changes shorter than the given window.
edge	Emits an event pulse on any transition, in either direction.
else	Keyword forming the fallback condition of a branch.
else-if	Keyword forming an additional condition of a branch.
expression	Applies an expression to the input and outputs the result.
falling-edge	Emits an event pulse on each high-to-low transition.
from-buffer	Reads a typed value out of a binary buffer at a given offset.
hash	Applies an md5 or sha1 hash to the input.
if	Keyword forming the first condition of a branch.
ignore-value	Drops values matching a test, repeating the last value that passed.
invert	Inverts a boolean, or negates a number.
latch-value	Holds a value until a reset expression evaluates true.
map	Applies a chain of operations to every element of an array.
max	Outputs the largest of the last N samples, filtering out short drops.
max-length	Truncates a string to a number of characters, or an array to a number of elements.
min	Outputs the smallest of the last N samples, filtering out short rises.
min-delta	Holds the last value until the input moves by at least the given amount.
object-keys	Emits an array of an object's keys, or of an array's indexes.
object-values	Emits an array of an object's values.
off-delay	Switches false only after the input has stayed false for the given time.
on-delay	Switches true only after the input has stayed true for the given time.
or	Combines the input with an expression result using a logical OR.
pattern-escape	Escapes a value so it can be embedded safely in a pattern.
pattern-match	Captures the part of a string matching a pattern.
pattern-replace	Replaces the part of a string matching a pattern.
pattern-test	Outputs true when a pattern is present in the string.
rate-of-change	Outputs the change between samples divided by the time between them.
reject	Removes elements matching a test from an array.
resample	Resamples a stream to a fixed sample rate.
rising-edge	Emits an event pulse on each low-to-high transition.
source	Names the data source — pin, register, tag, or another variable — that feeds the chain.
state	Emits a constant value based on a series of expression tests, like an if/else-if/else.
threshold	Converts a numeric value to digital high or low at a cutoff.
to-buffer	Converts a value into a binary buffer.
toggle	Flips between true and false on each rising edge.
trim	Removes whitespace and non-printable characters from both ends of a string.
value-change	Emits an event pulse each time the value changes.
value-decrease	Emits an event pulse each time the value decreases.
value-increase	Emits an event pulse each time the value increases.
value-increase-diff	Emits the size of each increase, then returns to zero.
when-unavailable	Substitutes a value when the input is UNAVAILABLE.
window-count	Counts the events seen within a trailing time window.