ANSI Common Lisp   22 Printer   22.3 Formatted Output   22.3.4 FORMAT Printer Operations

22.3.4.3 Tilde W: Write

An argument, any object, is printed obeying every printer control variable (as by write). In addition, ~W interacts correctly with depth abbreviation, by not resetting the depth counter to zero. ~W does not accept parameters. If given the colon modifier, ~W binds *print-pretty* to true. If given the at-sign modifier, ~W binds *print-level* and *print-length* to nil.

~W provides automatic support for the detection of circularity and sharing. If the value of *print-circle* is not nil and ~W is applied to an argument that is a circular (or shared) reference, an appropriate #n# marker is inserted in the output instead of printing the argument.