Originally posted by: carope

Hello, 

i do have a problem to define dexpr for my OPL Model. I have a dynamic model with demand functions different for each period and quality. I defined a range "time"{1..2} and a set "quality" {good, bad}. 

The usual way to declare a dexpr named demand is: 

dexpr float demand [q in quality][t in time] = a[t]+b[t]+c[t];

So the demand for all q/t combinations is the same "a[t]+b[t]+c[t]". 

Unfortunately, I have different demand functions for each quality/time combination (or matrix-field). This means if q in quality is "good" and time is "1" (e.g. a[t]+b[t]+c[t]) it is a different function than for quality"bad" and time"1" (d[t]+e[t]+f[t]) and so on.  I need this dexpr for further use in a similar way.

So my question is, is there any way to declare dexpr like 

dexpr float demand [q in quality: q!="bad"][t in time:t==1] = a[t]+b[t]+c[t];

or 

dexpr float demand ["good"][1] = a[t]+b[t]+c[t]; ???

OPL says it is not possible to use filter in generic arrays. Any ideas how to work around that without defining dexpr like demand_good_1 and so on? 

Thanks for ideas in advance!

Hi

have you thought about using the ternary operator ?

dexpr float demand [q in quality][t in time] = (t==1)?(expr1):(expr2);

?

regards

Originally posted by: carope

Hi, 

i didn't know about that operator before, but this is exactly the right one.

Thanks a lot!