# T427

> invalid lambda parameter list

**Severity** Error

The lambda has the wrong number of parameters for the method it is passed to. `map`, `filter`, `any`, `all` and `count` take a one-parameter lambda (`v => ...`); `reduce` takes an accumulator and an element (`(acc, v) => ...`) with two different names.

Adjust the parameter list to the method.

## Failing example

```flowscope
script "Sum of large prints"
data tape = subscribe(data.trades, minNotional: 100_000.0)
state recent = rolling<float>(20)
on tape.trade(tr) {
  recent.push(tr.notional)
  let total = recent.reduce(0.0, v => v + v)
  log.debug(str.formatVolume(total))
}
```

## Fixed example

```flowscope
script "Sum of large prints"
data tape = subscribe(data.trades, minNotional: 100_000.0)
state recent = rolling<float>(20)
on tape.trade(tr) {
  recent.push(tr.notional)
  let total = recent.reduce(0.0, (acc, v) => acc + v)
  log.debug(str.formatVolume(total))
}
```

## Related

- [T426](/docs/scripting/reference/diagnostics/t426)