Synopsis
Generate an error condition
Usage
error (String_Type msg
Description
The
error function generates a
SLang error condition causing
the interpreter to start unwinding to top-level. It takes a single
string parameter which is displayed on the stderr output device.
The error condition may be cleared via an
ERROR_BLOCK with the
_clear_error function. Consult \user-manual for more
information.
Example
define add_txt_extension (file)
{
if (typeof (file) != String_Type)
error ("add_extension: parameter must be a string");
file += ".txt";
return file;
}
See also
Synopsis
Print a string onto the message device
Usage
message (String_Type s
Description
The message function will print the string specified by
s onto the message device.
Example
define print_current_time ()
{
message (time ());
}
Notes
The message device will depend upon the application. For example,
the output message device for the jed editor correspond to the
line at the bottom of the display window. The default message
device is the standard output device.
See also
Synopsis
Generate a usage error
Usage
usage (String_Type msg)
Description
The usage function generates a usage exception and displays
msg to the message device.
Example
Suppose that some function
plot plots an array of
x and
y values. The such a function could be written to issue a
usage message if the wrong number of arguments were passed:
define plot ()
{
variable x, y;
if (_NARGS != 2)
usage ("plot (x, y)");
(x, y) = ();
% Now do the hard part
.
.
}
See also
Synopsis
Generate an error condition
Usage
verror (String_Type fmt, ...)
Description
The
verror function performs the same role as the
error
function. The only difference is that instead of a single string
argument,
verror takes a sprintf style argument list.
Example
define open_file (file)
{
variable fp;
fp = fopen (file, "r");
if (fp == NULL) verror ("Unable to open %s", file);
return fp;
}
Notes
In the current implementation, strictly speaking, the
verror
function is not an intrinsic function. Rather it is a predefined
SLang function using a combination of
Sprintf and
error .
See also
Synopsis
Print a formatted string onto the message device
Usage
vmessage (String_Type fmt, ...)
Description
The vmessage function formats a sprintf style argument list
and displays the resulting string onto the message device.
Notes
In the current implementation, strictly speaking, the
vmessage
function is not an intrinsic function. Rather it is a predefined
SLang function using a combination of
Sprintf and
message .
See also