Re: [U2] [UV] reference a variable indirectly?

[Mats Carlid]

Barry Brevik wrote:
UV 9.6.1.3 on Windows.
For the longest time this has been bugging me, but right now I could really
use this capability.
Does anyone know if it is possible to reference a variable indirectly? IOW,
I want to be able to store variable names in a file (for example), and then
assign values to those variables as the program encounters them.
For example, something like this:
PARTNO = ''; LOTNO = ''; PARTNAME = ''
VAR.NAMES = 'PARTNO':@FM:'LOTNO':@FM:'PARTNAME'
*
* Next, a magic command that makes the variable
* refered to by VAR.NAMES<2> equal to 'it works'.
(VAR.NAMES<2>) = 'it works'; * I know this does not work, just example.
PRINT LOTNO
*
* Variable LOTNO is now eq 'it works'.
Possible??
Barry
 

No there is no way to do that. You'd need an 'eval' function/statement.
But You can do something similar with a subroutine and a function.
Subroutine   SET( variable name,  value )
Function  VAL( variable name )
They need to share a common ( or a file ) where variable-value pairs are 
stored.

A straight forward implementation would be to search for the variable name
in an mv-string and use the index to look up the value from another mv
string.  If  you know the number of entries you can use arrays.
Even if you don't you can still use arrays by running imformation style 
allowing
them to be redimensioned.

Then Your program would look like:
 DEFFUN  VAL( var )  CALLING "VAL"
 CALL  SET( 'LOTNO', 'it works' )
 PRINT VAL( 'LOTNO' )
----------------------------
Naive untested implementation. If heavily used you'd need to hash
e.g.  as MOD( SEQ(VAR[1,1])*LEN(VAR), N )+1   where N is the
number of hash points  and the dimension of  VARS and VALS.
SUBROUTINE  SET( VAR, VAL)
COMMON /..SET/  VARS, VALS
LOCATE VAR IN VARS<1> SETTING II THEN
    VALS<II> = VAL
    END
ELSE
    VARS<-1> = VAR
    VALS<-1> = VAL
    END
RETURN
END

FUNCTION  VAL( VAR )
!!  Hashed version
COMMON /..SET/ VARS(N), VALS(N)
HASH =  MOD( SEQ(VAR[1,1])*LEN(VAR), N )+1
RES = ""
LOCATE VAR IN VARS(HASH)<1> SETTING II THEN
   RES =  VALS(HASH)<II>
   END
RETURN (RES)
END
-- mats
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