System Function DL
⎕DL or system function Quad DL is available in monadic form only.
|R is - normally a number greater than zero.|
|Z returned by APL's interpreter - is a scalar number, showing exactly how many actual seconds APL was delayed and Z's value is normally somewhat close to input R's value.|
Monadic system function ⎕DL is similar to a sleep or thread sleep routine in other languages.
The following pauses NARS APL program execution for roughly greater than six and a half seconds:
R was 6.651 (user specified). Z returned was 6.646. This system function is useful where concurrent/simultaneous processes are running or APL may be dependent on an external routine/program which is running and that external routine needs to finish first, so for example APL can read in the external results. If ⎕DL is used in a user function, say within a loop, every R seconds your APL function can check for that external result, e.g. existence of a file, value within that file, etc.
|System Variables (A value may be assigned to these except for ⎕DM)|
|Niladic System Functions (a value cannot be assigned to these)|
|Monadic or dyadic system functions (a value cannot be assigned to these)|
|Note that quad functions and variables are case insensitive|