Helper Functions (q.*)

QSL provides 12 global helper functions in the q namespace for common trading logic.

Quick Reference

Function	Signature	Returns
`q.crossOver`	`(seriesA, seriesB, i)`	`boolean`
`q.crossUnder`	`(seriesA, seriesB, i)`	`boolean`
`q.highest`	`(series, period, i)`	`number`
`q.lowest`	`(series, period, i)`	`number`
`q.sma`	`(series, period, i)`	`number`
`q.isNaN`	`(value)`	`boolean`
`q.clamp`	`(value, min, max)`	`number`
`q.between`	`(value, min, max)`	`boolean`
`q.pctChange`	`(a, b)`	`number`
`q.sign`	`(value)`	`-1 \| 0 \| 1`
`q.abs`	`(value)`	`number`
`q.round`	`(value, decimals)`	`number`

Crossover Detection

q.crossOver(seriesA, seriesB, i)

Returns true when seriesA crosses above seriesB at bar i. Compares current and previous bar values to detect the crossing.

if (q.crossOver(ctx.ind.fastEma, ctx.ind.slowEma, i)) {
  ctx.order.market('ASSET', 1, { signal: 'buy' });
}

q.crossUnder(seriesA, seriesB, i)

Returns true when seriesA crosses below seriesB at bar i.

if (q.crossUnder(ctx.ind.fastEma, ctx.ind.slowEma, i)) {
  ctx.order.close('ASSET', { signal: 'sell' });
}

Lookback Functions

q.highest(series, period, i)

Returns the highest value in the last period bars ending at i.

const highest20 = q.highest(ctx.series.high, 20, i);

q.lowest(series, period, i)

Returns the lowest value in the last period bars ending at i.

const lowest20 = q.lowest(ctx.series.low, 20, i);

q.sma(series, period, i)

Returns the simple moving average over the last period bars ending at i. Useful for quick calculations inside onBar without declaring a full indicator.

const avgVolume = q.sma(ctx.series.volume, 20, i);
if (ctx.series.volume[i] > avgVolume * 2) {
  // Volume spike detected
}

Validation

q.isNaN(value)

Returns true if the value is NaN. Essential for checking whether an indicator has enough bars to produce valid output.

if (q.isNaN(ctx.ind.ema[i])) return; // Indicator not ready

Math Utilities

q.clamp(value, min, max)

Constrains a value within the range [min, max].

const size = q.clamp(rawSize, 0.1, 5); // Limit position size

q.between(value, min, max)

Returns true if value is within [min, max] (inclusive).

if (q.between(ctx.ind.rsi[i], 30, 70)) {
  // RSI in neutral zone
}

q.pctChange(a, b)

Returns the percentage change from b to a as a decimal (e.g., 0.05 for 5%).

const change = q.pctChange(ctx.series.close[i], ctx.series.close[i - 1]);
if (change > 0.03) {
  // Price jumped more than 3%
}

q.sign(value)

Returns -1, 0, or 1 indicating the sign of the value.

const direction = q.sign(ctx.ind.macd.histogram[i]);

q.abs(value)

Returns the absolute value.

const spread = q.abs(ctx.ind.fastEma[i] - ctx.ind.slowEma[i]);

q.round(value, decimals)

Rounds a value to the specified number of decimal places.

const price = q.round(ctx.series.close[i] * 1.02, 2); // 2% above, 2 decimals

Example: Using Multiple Helpers

function onBar(ctx, i) {
  const ema = ctx.ind.ema;
  const close = ctx.series.close;
  
  // Skip if indicator not ready
  if (q.isNaN(ema[i])) return;
  
  // Trend filter: price above 20-bar high
  const above20High = close[i] > q.highest(close, 20, i - 1);
  
  // Volume filter: above-average volume
  const highVolume = ctx.series.volume[i] > q.sma(ctx.series.volume, 20, i);
  
  // Entry on bullish crossover with filters
  if (above20High && highVolume && ctx.position('ASSET').qty === 0) {
    if (q.crossOver(ctx.ind.fastEma, ctx.ind.slowEma, i)) {
      const size = q.clamp(1, 0.5, 3);
      ctx.order.market('ASSET', size, { signal: 'buy' });
    }
  }
  
  // Exit on bearish crossover
  if (q.crossUnder(ctx.ind.fastEma, ctx.ind.slowEma, i)) {
    ctx.order.close('ASSET', { signal: 'sell' });
  }
}

onBar() — Where helpers are used
Indicators — Declaring indicators