Common Lisp's FORMAT function is—along with the extended LOOP macro—one of the two Common Lisp features that inspires a strong emotional response in a lot of Common Lisp users. Some love it; others hate it.1

FORMAT's fans love it for its great power and concision, while its detractors hate it because of the potential for misuse and its opacity. Complex FORMAT control strings sometimes bear a suspicious resemblance to line noise, but FORMAT remains popular with Common Lispers who like to be able to generate little bits of human-readable output without having to clutter their code with lots of output-generating code. While FORMAT's control strings can be cryptic, at least a single FORMAT expression doesn't clutter ...

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