ŒES Error simulate

One-argument form

ŒES can simulate a predetermined or programmer-defined error, in a form compatible with IBM's APL2. If the right argument is a character vector or scalar, ŒET is set to 0 1 and the right argument is used as the error message. A two element integer right argument will generate the appropriate error message (if the argument corresponds to a valid value for ŒET) or no error message (if there is no corresponding value for ŒET). An empty vector right argument causes no action to be taken, whilst a right argument of 0 0 resets error messages and codes (ŒEM ŒERM ŒET ŒLER).

             ’R„A DIVIDE B
       [1]   ŒES(B=0)/'ATTEMPT TO DIVIDE BY ZERO'
       [2]   R„A÷B
             ’   1.43.05 05/28/90

             3 DIVIDE 0
       ATTEMPT TO DIVIDE BY ZERO     (Message displayed)
             3 DIVIDE 0
             ^
             ŒET                     (ŒET set to 0 1)
       0 1
             ŒLER                    (1†ŒLER set to 15 - unknown error)
       15 0

             ’R„A DIVIDE B
       [1]   ŒES(B=0)/5 4            (Signal the standard error)
       [2]   R„A÷B
             ’   1.44.32 05/28/90
             5 DIVIDE 0
       DOMAIN ERROR                  (Standard message shown)
             5 DIVIDE 0
             ^
             ŒET                     (Standard values for ŒET, ŒLER)
       5 4
             ŒLER
       11 0

Using an argument to ŒES that does not correspond to a error code of ŒET causes no error message to display.

             ’DOIT
       [1]   ŒES 101 45              (Outside the ŒET range)
             ’   1.45.48 05/28/90
             DOIT
             DOIT                    (No error message displayed)
             ^
             ŒET                     (ŒET takes chosen value)
       101 45
             ŒLER                    (ŒLER takes ¯1 value)
       ¯1 0

Two-argument form

The two-argument form of ŒES can be used to signal both an Error Type and an Error Message. The left argument should be a character scalar or vector which will be used as the error message portion of ŒEM and ŒERM and the right argument should be a two element integer vector which will be assigned to ŒET. The left argument overrides the usual error message associated with a given value of ŒET. If the right argument is empty, no error is signalled. If it is 0 0 any left argument is ignored and error messages and reports are reset (ŒET ŒLER ŒEM ŒERM).

             ’R„A DIVIDE B
       [1]   ŒES(B=0)/5 4
       [2]   R„A÷B
             ’   1.32.25 05/29/90
             3 DIVIDE 0              (Standard error message)
       DOMAIN ERROR
             3 DIVIDE 0
             ^
             ŒET                     (Standard error codes)
       5 4
             ŒLER
       11 0
             ’R„A DIVIDE B
       [1]   'ATTEMPT TO DIVIDE BY ZERO' ŒES(B=0)/5 4
       [2]   R„A÷B                   (Redefined error message)
             ’   1.33.27 05/29/90
             3 DIVIDE 0
       ATTEMPT TO DIVIDE BY ZERO     (New error message)
             3 DIVIDE 0
             ^
             ŒET                     (Standard ŒET)
       5 4
             ŒLER
       11 0