An iolist isn't a string, you can't pass it to the uppercase function for instance. It's really meant for I/O as the name implies. Regular string concatenation

An iolist isn't a string, you can't pass it to the uppercase function for instance. It's really meant for I/O as the name implies. Regular string concatenation is optimized to avoid copying when possible: https://www.erlang.org/doc/system/binaryhandling.html#constructing-binaries https://www.erlang.org/doc/system/binaryhandling.html#constr...