Loops

Prefer for`forto` to while`while`. [FIXME: needs RFC]

A for`forloop is preferable to awhileloop, unless the loop counts in a non-uniform way (making it difficult to express usingfor`).

Guidelines for loop`loop`. [FIXME]

[FIXME] When is loop`looprecommended? Some possibilities: * For optimistic retry algorithms * For servers * To avoid mutating local variables sometimes needed to fitwhile`