Guile exports a simple formatted output function, simple-format.
For a more capable formatted output facility, See Formatted Output.
Write message to destination, defaulting to the current
output port. message can contain ~A and ~S escapes.
When printed, the escapes are replaced with corresponding members of
args: ~A formats using display and ~S formats
using write. If destination is #t, then use the
current output port, if destination is #f, then return a
string containing the formatted text. Does not add a trailing newline.
Somewhat confusingly, Guile binds the format identifier to
simple-format at startup. Once (ice-9 format) loads, it
actually replaces the core format binding, so depending on
whether you or a module you use has loaded (ice-9 format), you
may be using the simple or the more capable version.