System Variable DM

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⎕DM - Diagnostic Message

⎕DM Diagnostic Message set to last error message the APL interpreter encountered.
Unlike other system variables, ⎕DM cannot be assigned a value by the User. The APL interpreter sets its value when it encounters an error, e.g. DOMAIN ERROR.


⎕DM is set by APL to the last diagnostic error message the Interpreter encountered. It is for informational and diagnostic purposes only. User cannot set its value.

⎕DM is useful for viewing the last error message, particularly if Error Trapping is being used, or for system-function and user-function debugging purposes. For example:

      ⎕DM

      ⍴⎕DM   ⍝ In a CLEAR APL Workspace ⎕DM's value is an empty character vector
0
      +
SYNTAX ERROR
      +
      ∧
      ⍴⎕←⎕DM
SYNTAX ERROR
      +
      ∧
28

⎕DM is a system variable. An APL error in the right argument of ⎕EA will send a diagnostic message to ⎕DM, as well as a triggering error event for ⎕ELX.

See Also: ⎕ELX and ⎕EA


System Variables (A value may be assigned to these except for ⎕DM)
ALX CT DM DT ELX FC FEATURE FPC IC IO
LR LX PP PR PW RL SA WSID
Niladic System Functions (a value cannot be assigned to these)
A AV EM ET LC NNAMES NNUMS SI SYSID SYSVER
T TC TCBEL TCBS TCESC TCFF TCHT TCLF TCNL TCNUL
TS WA
Monadic or dyadic system functions (a value cannot be assigned to these)
AT CR DC DFT DL DR EA EC ERROR ES
EX FMT FX MF NAPPEND NC NCREATE NERASE NINFO NL
NLOCK NREAD NRENAME NREPLACE NRESIZE NSIZE NTIE NUNTIE STOP TF
TRACE UCS VR
Note that quad functions and variables (except for the ⎕A family of functions) are case insensitive


See Also
System Commands System Variables and Functions Operators


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