We're thankfully in a world these days where all the relevant implementations are sane and reliable for most real usage, but a couple decades back that was very

We're thankfully in a world these days where all the relevant implementations are sane and reliable for most real usage, but a couple decades back that was very much the practical reality. Intel's x87 instruction set was infamous for this. Transcendentals like fsin would sometimes have fewer than a dozen bits correct and worse, the documentation on it was straight up wrong until Bruce Dawson on the chrome team filed a bug report.