Printing Other Arrays

ToC

Allegro CL

ANSI Common Lisp

22 Printer

22.1 The Lisp Printer

22.1.3 Default Print-Object Methods

22.1.3.8 Printing Other Arrays

If *print-array* is true and *print-readably* is false, any array other than a vector is printed using #nA format. Let n be the rank of the array. Then # is printed, then n as a decimal integer, then A, then n open parentheses. Next the elements are scanned in row-major order, using write on each element, and separating elements from each other with whitespace₁. The array's dimensions are numbered 0 to n-1 from left to right, and are enumerated with the rightmost index changing fastest. Every time the index for dimension j is incremented, the following actions are taken:

If j < n-1, then a close parenthesis is printed.
If incrementing the index for dimension j caused it to equal dimension j, that index is reset to zero and the index for dimension j-1 is incremented (thereby performing these three steps recursively), unless j=0, in which case the entire algorithm is terminated. If incrementing the index for dimension j did not cause it to equal dimension j, then a space is printed.
If j < n-1, then an open parenthesis is printed.

This causes the contents to be printed in a format suitable for :initial-contents to make-array. The lists effectively printed by this procedure are subject to truncation by *print-level* and *print-length*.

If the array is of a specialized type, containing bits or characters, then the innermost lists generated by the algorithm given above can instead be printed using bit-vector or string syntax, provided that these innermost lists would not be subject to truncation by *print-length*.

If both *print-array* and *print-readably* are false, then the array is printed in a format (using #<) that is concise but not readable.

If *print-readably* is true, the array prints in an implementation-defined manner; see the variable *print-readably*. In particular, this may be important for arrays having some dimension 0.

For information on how the Lisp reader parses these "other arrays," see Section 2.4.8.12 Sharpsign A.