Output Printing

MzScheme's printer follows these non-standard rules:

• A vector can be printed by write and print using the shorthand described in section 14.3, where the vector's length is printed between the leading # and the opening parenthesis and repeated tail elements are omitted. For example, #(1 2 2 2) is printed as #4(1 2). The display procedure does not output vectors using this shorthand. Shorthand vector printing is controlled with the print-vector-length Boolean parameter (see section 9.4.1.4). Shorthand vector printing is enabled by default.

• Boxes (see section 4.9) can be printed with the #& notation (see section 14.3). When box printing is disabled, all boxes are printed as #<box>. Box printing is controlled with the print-box Boolean parameter (see section 9.4.1.4). Box printing is enabled by default.

• Structures (see Chapter 5) can be printed using vector notation. In the vector, the first item is a symbol of the form struct:s -- where s is the name of the structure -- and the remaining elements are the elements of the structure. When structure printing is disabled, structures are printed as #<struct:s>. Structure printing is controlled with the print-struct Boolean parameter (see section 9.4.1.4). Structure printing is disabled by default.

• Symbols containing spaces or special characters write using escaping backslashes and quoting vertical bars. Symbols are quoted with vertical bars or a leading backslash when they would otherwise print the same as a numerical constant. If the value of the read-accept-bar-quote Boolean parameter is #f (see section 9.4.1.3), then backslashes are always used to escape special characters instead of quoting them with vertical bars, and a vertical bar is not treated as a special character. See section 14.3 for more information about symbol parsing. Symbols display without escaping or quoting special characters.

• Characters with the special names described in section 14.3 write using the same name. (Some characters have multiple names; the #\newline and #\nul names are used instead of #\linefeed and #\null). All other characters write as #\ followed by the single-byte character value. All characters display as the single-byte character value.

• S-expressions with shared structure can be printed using #n= and #n#, where n is a decimal integer. See section 14.5.