# Flipped inputs pass silently

> Feed a calculation the right number the wrong way round and nothing crashes. In a signal, you trade the opposite strategy.

Building block · Getting the numbers right · found 2026-09-26 · by John Kingola

## What I was looking for

Bugs that still produce plausible numbers, in an Expert Advisor audit and across trading libraries.

## What I found

Oldest bar for newest, losses for wins, excess kurtosis for raw: the result is still a number of the right type in the right range. The report fills in and the number gets trusted.

barter-rs fed its win rate the loss count, so it reported 0.30 where the answer was 0.70; three independent libraries agreed on the right value. An MT5 Expert Advisor I audited read its price arrays oldest-first and sold on a bullish MACD cross. Both the issue reporter and the author had missed it.

## The move

I test against a known answer, not against "it runs": type and range checks cannot see a flip.

Web version: https://kingola.dev/notes/flipped-inputs-pass-silently/