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data/format

(format out str &args)

Macro defined at lib/data/format.lisp:120:2

Output the string STR formatted against ARGS to the stream OUT. In the case OUT is nil, a string in returned; If OUT is true, the result is printed to standard output.

Formatting specifiers

Formatting specifiers take the form {...}, where ... includes both a reference (what’s to be output) and a formatter (how to output it).

  • If the reference starts with #, it is an implicit named symbol (something in scope, and not passed explicitly).
  • If the reference starts with an alphabetic character, it is named: something given to the format macro explicitly, as a keyword argument.
  • If the reference starts with $, it is a positional argument.

The formatter can either start with :, in which case it references an Urn symbol, or start with %, in which case it is a string.format format sequence.

Examples

> (format nil "{#pretty:pretty} is {what}" :what 'pretty)
out = "«method: (pretty x)» is pretty"
> (format nil "0x{foo%x}" :foo 123)
out = "0x7b"