The number is wrong and nothing errored
No exception, no log line, no red. The value on the screen is simply not the value it should be — and every one of these is a measured case of exactly that.
Curated by Code Recycle Editorial
- 1
The sanitizer that turns "$25M" into 25 doesn't throw. It saves, renders $25, and looks completely normal.
Why it's here: "$25M" is stored as 25. It saves, renders $25, and looks completely normal.
- 2
22 of 28 results wrong across four popular libraries. The value becomes 25 and the page renders normally.
Why it's here: 22 of 28 results wrong across four popular libraries, and the page renders fine.
- 3
Adding metres to feet produces a perfectly plausible number and no error at all.
Why it's here: Adding metres to feet produces a perfectly plausible number.
- 4
The textbook variance formula can return a NEGATIVE number, and its square root renders as a blank rather than an error.
Why it's here: The textbook variance formula can return a negative number; its root renders blank.
- 5
The mean of three p99s is not the p99. Every multi-instance dashboard does it, and the number is always too low.
Why it's here: The mean of three p99s is not the p99, and it is always too low.
- 6
Financial code without double-entry discipline does not crash when it loses money. It reports a number that is slightly wrong forever.
Why it's here: Financial code without double-entry discipline does not crash when it loses money.
- 7
Split a pool across contributors so the cents always add up. Rounding is where this quietly goes wrong.
Why it's here: Splitting a pool is where rounding quietly costs somebody their cents.