FlowscopeDocs

T106

invalid map key type

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Severity Error

Map keys must be string, int or bool. Floats are rejected because two prices that print the same can differ in their last bit, so lookups would miss; colors, times and records are not supported as keys either.

For price-keyed maps, convert the price to an integer tick index (int(math.round(price / context.tickSize))) and use that as the key.

Failing example

Flowscope Script
script "Volume at price"
data chart = subscribe(data.ohlcv)
state byPrice = map<float, float>(2000)
on chart.close {
  let c = chart.close
  if c != null {
    byPrice[c] = (byPrice[c] ?? 0.0) + (chart.volume ?? 0.0)
  }
}

Fixed example

Flowscope Script
script "Volume at price"
data chart = subscribe(data.ohlcv)
state byTick = map<int, float>(2000)
on chart.close {
  let c = chart.close
  if c != null {
    let key = int(math.round(c / context.tickSize)) ?? 0
    byTick[key] = (byTick[key] ?? 0.0) + (chart.volume ?? 0.0)
  }
}