X-Function Exception Handling

The example below illustrates trapping an X-Function error with LabTalk, so that an X-Function call that is likely to generate an error does not break your entire script.

For X-Functions that do not return an error code, two functions exist to check for errors in the last executed X-Function: xf_get_last_error_code() and xf_get_last_error_message()$. These functions should be used in situations where the potential exists that a particular X-Function could fail.

In this example, the user is given the option of selecting a file for import, but if that import fails (e.g. user picked file type inappropriate for the import) we need to handle the remaining code.

dlgfile gr:=*.txt;  // Get the file name and path from user
impasc -se;  // Need to use -se switch for execution to continue, see note below
if( 0 != xf_get_last_error_code() )
    strError$ = "XFunction Failed: " + xf_get_last_error_message()$;
    type strError$;
    break 1;  // Stop execution
// Data import probably succeeded, so our script can continue
type continuing...;

Note the use of the general X-Function option -se to suppress error messages. You can also use -sl to suppress error logging and -sb to suppress both. It is necessary to use one of these options in order for script execution to continue to the next line when the X-Function call fails.

Looping Over to Find Peaks

In the following example, we loop over all columns in a worksheet to find peaks. If no peak is found in a particular column, the script continues with the rest of the columns. It is assumed here that a worksheet with suitable data is active.

//import data
string fn$=system.path.program$ + "Samples\curve fitting\Asymmetric Gaussian.dat";
impasc fname:=fn$ ;
//loop over all columns
for(int ii=1; ii<=wks.ncols; ii++)
  // Find peak in current column, suppress error message from XF
  Dataset mypeaks;
  pkfind $(ii) ocenter:=mypeaks -se; // Need to use -se for execution to continue
  // Check to see if XF failed
  if( 0 != xf_get_last_error_code() )
    type "Failed on column $(ii): %(xf_get_last_error_message()$)";
    type Found $(mypeaks.getsize()) peaks in column $(ii);