Exceptions

• debug-info-handler: parameter for a procedure of no arguments. This debug info handler is called to fill in the debug-info field of an exception structure. The default debug info handler returns void.
• current-exception-handler: parameter for a procedure that is invoked to handle an exception. See section 8.1 for more information about exceptions.
• error-display-handler: parameter for a procedure that takes a string to print as an error message. This error display handler is called by the default exception handler. The default error display handler displays its argument to the current error port (determined by the current-error-port parameter). To report a run-time error, use raise (see section 8.1) or error (see section 8.2) instead of calling the error display procedure directly. If an exception is raised while the error display handler is executing, an error message is printed using a primitive error printer and the primitive error escape handler is invoked.
• error-print-width: parameter for an integer greater than 3. This value is used as the maximum number of characters used to print a Scheme value that is embedded in a primitive error message.
• error-value->string-handler: parameter for a procedure that takes an arbitrary Scheme value and an integer and returns a string. This error value conversion handler is used to to print a Scheme value that is embedded in a primitive error message. The integer argument to the handler specifies the maximum number of characters that should be used to represent the value in the resulting string. The default error value conversion handler writes the value into a string; if the printed form is too long, the printed form is truncated and the last three characters of the return string are set to ``...''.

  If the string returned by an error value conversion handler is longer than requested, the string is destructively ``truncated'' by setting the first extra position in the string to the null character. If a non-string is returned, then the string "..." is used. If a primitive error string needs to be generated before the handler has returned, the default error value conversion handler is used.