SRFI 28 - Basic format strings

Specifies a method of interpreting a Scheme string which contains a number of escape sequences, into which other data is interpolated according to the semantics of each sequence.

See the [SRFI document][http://srfi.schemers.org/srfi-28/srfi-28.html] for more information.

Limitations

Currently, this translates newline escape sequences into LF. This may cause issues if this is ever used on Windows (which expects CRLF instead). Given that Cyclone does not currently support Windows, this issue should not arise in practice.

Interface

format

(format format-string [obj ...])

Processes format-string, replacing any escape sequences in order with one or more characters. These characters depend on the semantics of the escape sequence.

An ‘escape sequence’ is a two-character sequence in format-string, where the first character is a tilde (‘~’). The following are all of the valid escape codes, as well as their semantics:

• ~a: The corresponding value is inserted into the string as if printed by display.
• ~s: The corresponding value is inserted into the string as if printed by write.
• ~%: A newline is inserted.
• ~~: A literal tilde is inserted.

~a and ~s, when encountered, require a corresponding Scheme value to be present as an argument to format. The values provided in obj ... are used by the escape sequences in order. It is an error if fewer values are provided than escape sequences which require them. ~% and ~~ do not need a corresponding value.

Example: The call (format "This is the ~ast example: ~s~%" 1 '(foo bar 17)) would produce the string "This is the 1st example: (foo bar 17) " (note the newline).