Definition examples

Three runnable definition scripts, simple → complex. Each marks setups for Collect — they do not measure outcomes (that is a study).

In Code the API word is flow (kind: "flow"). In the product UI the noun is always Definition.

Simple → complex

1. Bull bar

Marks every bar that closes above its open. Payload carries bar range for later studies.

What it defines

A Collectable event bull_bar whenever close > open.

Key decisions

Full script

meta({
  name: "Bull bar",
  kind: "flow",
  slug: "bull-bar",
  shortName: "BullBar",
});

events.declare({
  id: "bull_bar",
  intent: "Mark closes above open",
  payload: {
    range: { type: "number", description: "High minus low" },
    close: { type: "number", description: "Close price" },
  },
  paint: "pin",
});

outputs.declare({
  id: "close_line",
  kind: "line",
  name: "Close",
  color: "#64b5f6",
});

export function onBar(ctx) {
  ctx.plot("close_line", ctx.close);

  if (ctx.close <= ctx.open) return;

  const range = ctx.high - ctx.low;
  ctx.emit(
    "bull_bar",
    { range, close: ctx.close },
    {
      label: `Bull · R=${range.toFixed(2)}`,
      subtitle: `close ${ctx.close.toFixed(2)}`,
      price: ctx.close,
      timeStart: ctx.time,
    }
  );
}

2. EMA cross

Fires when a fast EMA crosses above a slow EMA. Uses the public Moving Average indicator as a dependency instead of re-implementing EMA math.

What it defines

Event ema_cross_up on the bar where fast MA crosses from at-or-below slow MA to above it.

Key decisions

Full script

meta({
  name: "EMA cross up",
  kind: "flow",
  slug: "ema-cross-up",
  shortName: "EmaXUp",
});

indicators.declare({
  slug: "ma",
  as: "fast",
  version: 1,
  settings: { period: 9, maType: "EMA" },
});

indicators.declare({
  slug: "ma",
  as: "slow",
  version: 1,
  settings: { period: 21, maType: "EMA" },
});

events.declare({
  id: "ema_cross_up",
  intent: "Fast EMA crosses above slow EMA",
  payload: {
    fast: { type: "number", description: "Fast EMA" },
    slow: { type: "number", description: "Slow EMA" },
    close: { type: "number", description: "Close at cross" },
  },
  paint: "pin",
  oncePer: { keys: ["session"], windowBars: 1 },
});

outputs.declare({ id: "fast_line", kind: "line", name: "Fast", color: "#26a69a" });
outputs.declare({ id: "slow_line", kind: "line", name: "Slow", color: "#ef5350" });

export function onBar(ctx) {
  const fast = ctx.indicators.fast?.value;
  const slow = ctx.indicators.slow?.value;
  if (fast == null || slow == null) return;

  ctx.plot("fast_line", fast);
  ctx.plot("slow_line", slow);

  // Identity update returns the stored prior values without changing them.
  const prevFast = ctx.accum("prevFast", null, (prev) => prev);
  const prevSlow = ctx.accum("prevSlow", null, (prev) => prev);

  if (prevFast != null && prevSlow != null && prevFast <= prevSlow && fast > slow) {
    ctx.emit(
      "ema_cross_up",
      { fast, slow, close: ctx.close },
      {
        label: "EMA cross ↑",
        subtitle: `${fast.toFixed(2)} > ${slow.toFixed(2)}`,
        price: ctx.close,
        timeStart: ctx.time,
      }
    );
  }

  ctx.accum("prevFast", null, () => fast);
  ctx.accum("prevSlow", null, () => slow);
}

Pin version to the library MA version you resolve in the builder when you can — agents should call resolve_dependency_contract before inventing shapes. See Declaring indicator dependencies.

3. Session opening-range break

Builds a session opening range from the first N bars after session open, then emits once when price breaks the high (or low) after the range is locked.

What it defines

Events or_break_up / or_break_dn with the OR high/low and break price — one break direction per session via oncePer.

Key decisions

Full script

meta({
  name: "OR break",
  kind: "flow",
  slug: "or-break",
  shortName: "ORBreak",
});

events.declare({
  id: "or_break_up",
  intent: "Close breaks above session opening range",
  payload: {
    orHigh: { type: "number", description: "Opening range high" },
    orLow: { type: "number", description: "Opening range low" },
    close: { type: "number", description: "Break close" },
    sessionKey: { type: "string", description: "Session key" },
  },
  paint: "pin",
  oncePer: { keys: ["session"] },
});

events.declare({
  id: "or_break_dn",
  intent: "Close breaks below session opening range",
  payload: {
    orHigh: { type: "number", description: "Opening range high" },
    orLow: { type: "number", description: "Opening range low" },
    close: { type: "number", description: "Break close" },
    sessionKey: { type: "string", description: "Session key" },
  },
  paint: "pin",
  oncePer: { keys: ["session"] },
});

outputs.declare({ id: "or_high", kind: "line", name: "OR high", color: "#26a69a" });
outputs.declare({ id: "or_low", kind: "line", name: "OR low", color: "#ef5350" });

const OR_BARS = 5;

export function onBar(ctx) {
  const s = ctx.session({});

  const st = ctx.accum("or", null, (prev) => {
    if (s.didOpen || prev == null) {
      return {
        key: s.key,
        bars: 1,
        high: ctx.high,
        low: ctx.low,
        locked: false,
      };
    }
    if (prev.locked) return prev;
    const bars = prev.bars + 1;
    const high = Math.max(prev.high, ctx.high);
    const low = Math.min(prev.low, ctx.low);
    return {
      key: s.key,
      bars,
      high,
      low,
      locked: bars >= OR_BARS,
    };
  });

  if (!st.locked) return;

  ctx.plot("or_high", st.high);
  ctx.plot("or_low", st.low);

  const base = {
    orHigh: st.high,
    orLow: st.low,
    close: ctx.close,
    sessionKey: st.key,
  };

  if (ctx.close > st.high) {
    ctx.emit("or_break_up", base, {
      label: "OR break ↑",
      subtitle: `H ${st.high.toFixed(2)}`,
      price: ctx.close,
      timeStart: ctx.time,
    });
  } else if (ctx.close < st.low) {
    ctx.emit("or_break_dn", base, {
      label: "OR break ↓",
      subtitle: `L ${st.low.toFixed(2)}`,
      price: ctx.close,
      timeStart: ctx.time,
    });
  }
}

Tune SessionOpts in IntelliSense for your market (exchange RTH vs named London/NY sessions). See Sessions.

Next

1. Emit and labels

2. Events and snapshots

3. First definition guide