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.so STk-man.macros
.TH report-error n 3.1 STk "STk procedure"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
report-error \- Command invoked to process errors
.SH SYNOPSIS
(\fBreport-error \fIhead message obj\fR)
.BE

.SH DESCRIPTION
.PP
\fBReport-error\fR is called by the interpreter when an error occurs.
This procedure is written in Scheme and can be by an application which
needs to handle redefined to handle errors. The \fIhead\fR argument is
a string which identify the kind of error. The \fIhead\fR argument
contains the error message and \fIobj\fR contains the object which 
causes the error (or the empty list when there is no object to incriminate).
.PP
The STk library includes a default \fBreport-error\fR procedure
that posts a dialog box containing the error message and offers
the user a chance to see a stack trace showing where the
error occurred and its associated environment.
.PP 
If an error occurs while is \fBreport-error\fR execution, the
interpreter detect that the procedure is buggy and it redirect further
messages on the standard error port.
.LP
Hereafter is a simple non-graphical error reporter.
.CS
(define (report-error head message obj)
  (let ((port (current-error-port)))
    ;; Display message
    (format port "~A: ~A ~S\n\n"  head message obj)
    ;; Display stack
    (let ((stack (%get-eval-stack))
	  (env   (%get-environment-stack)))
      (for-each (lambda (x y) (format port "~A ~A\n" x (uncode y)))
		env 
		stack))))
.CE