> So, the case is that the formatting string fits into memory, the data being formatted fits in memory but the output formatted text does not? It takes a minim

> So, the case is that the formatting string fits into memory, the data being formatted fits in memory but the output formatted text does not? It takes a minimum of twice as much memory to store the original data and its formatted stream. Some systems don't have much memory, and some systems work with large amounts of data. Some systems work with more data than fits in RAM, or more data than even fits on disk, or even infinite streams of data, from sensors or generated data. All of these use-cases must be accommodated by Hare. That said, you can easily format into a dynamically allocated string in Hare if you so desire: let s = fmt::asprintf("Hello, {}!", user); defer free(s); This has the obvious downside of requiring an additional memory allocation, which can also fail just as easily as I/O can, and must be freed after use. However, this function does not require I/O, so all of the I/O failure cases are ruled out. There are trade-offs between these two approaches. Hare's design is meant to let the user evaluate these trade-offs for their use-case and make an explicit, planned decision regarding their needs and potential failure modes.