RE: parameters - const, value, reference

["Joe Pluta" <joepluta@xxxxxxxxxxxxxxxxx>]

> From: Behalf Of Richard B Baird
>
> would you always specify const if you don't need or want the proc
> to change the data sent?

I use CONST primarily because I can use expressions.  If I have a parameter
that is 6.0 and I specify it as CONST, I can pass in not only a 6.0 field,
but anything that I could legally assign to a 6.0 field with an EVAL
statement, including literals (17) and expressions (myAge-25).

The nice thing about CONST as opposed to VALUE is that CONST can be used
with EXTPGM calls.  One good example is for QCMDEXC; if you specify the
length as CONST, you can pass in an expression such as %LEN(CmdString).  In
the following example, assume command, lib and file are all VARYING strings:

DQcmdexc          PR                  EXTPGM('QCMDEXC')
D Cmd                          128    const
D CmdLen                        15  5 const

C                   eval      command = 'CRTPF ' + lib + '/' + file
C                   callp     Qcmdexc(command:%len(command))

Joe