System Function DL

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⎕DL or system function Quad DL is available in monadic form only.

Monadic Function

Z←⎕DL R Delays APL program execution / pauses APL processing for the number of seconds specified in R. R should be a real number (representing seconds and it is not necessary for R to be a whole integer) and R should be greater than zero.
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:

       ⎕DL 6.651
6.646
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)
ALX CT DM DQ DT ELX FC FEATURE FPC IC
IO 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 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 are case insensitive