22.3.8.1 Tilde Left-Paren: Case Conversion

~(str~)

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?"