The contained control string str is processed, and what it produces is subject to case conversion.
With no flags, every uppercase character is converted to the corresponding lowercase character.
~:( capitalizes all words, as if by string-capitalize.
~@( capitalizes just the first word and forces the rest to lower case.
~:@( converts every lowercase character to the corresponding uppercase character.
In this example ~@( is used to cause the first word produced by ~@R to be capitalized:
(format nil "~@R ~(~@R~)" 14 14) => "XIV xiv" (defun f (n) (format nil "~@(~R~) error~:P detected." n)) => F (f 0) => "Zero errors detected." (f 1) => "One error detected." (f 23) => "Twenty-three errors detected."
When case conversions appear nested, the outer conversion dominates, as illustrated in the following example:
(format nil "~@(how is ~:(BOB SMITH~)?~)") => "How is bob smith?" NOT=> "How is Bob Smith?"