DEYIN LANGUAGE REFERENCE

Deyin pipelines are composed using the single pipeline operator |. All whitespace and newline breaks preceding pipe operators are ignored.

1. COMPLETE EBNF SPECIFICATION

pipeline   ::= "stream" CNAME "from" source ("|" step)*
source     ::= CNAME (STRING | CNAME)?
step       ::= window | filter | map | sink | compile

window     ::= "window" DURATION
filter     ::= "filter" EXPR
map        ::= "map" EXPR
sink       ::= "sink" "to" CNAME (STRING | CNAME)?
compile    ::= "compile" "to" CNAME

DURATION   ::= [0-9]+ ("s" | "m" | "h" | "d")
PERCENT    ::= [0-9]+ "%"
EXPR       ::= [^|\n]+

2. STAGE OPERATORS

KEYWORD	SYNTAX PATTERN	EXAMPLE
stream	stream <name> from <source> [arg]	stream ticks from kafka "market.BTC"
window	window <number><unit>	window 5m, window 30s, window 1h
filter	filter <boolean_expr>	filter price > 20 and rsi(14) < 30
map	map <assignment | signal>	map buy 10%, map delta = price - 100
sink	sink to <dest> [arg]	sink to stdout, sink to postgres "trades"
compile	compile to <python | wasm>	compile to python, compile to wasm

3. BUILT-IN TECHNICAL FUNCTIONS

FUNCTION	SIGNATURE	DESCRIPTION
rsi	rsi(period=14)	Calculates Relative Strength Index over the sliding window ring buffer
sma	sma(period=10)	Computes Simple Moving Average of price over period
ema	ema(period=10)	Computes Exponential Moving Average of price

4. EXPRESSION EVALUATION RULES

- Numeric Coercion: Fields like price, rsi, volume, and timestamp are automatically coerced to floating-point or integer values.
- Percentage Syntax: 10% evaluates to 0.10.
- Action Shorthands: buy 10% sets row["signal"] = "BUY 0.1"; sell all sets row["signal"] = "SELL".