Mathematica issue: Skip a loop step in Table

[Gueygel]

Hi everyone,

I have to do a list made of evaluations of a certain function, but if some condition is not satisfied, then I don't want to have the corresponding evaluation in my list. So I tried:

Flatten[Table[If[condition,f,{}],{i,imin,imax}]]

"condition" is true or false depending on the value of "i". If it is not satisfied, then an empty {} is written and Flatten takes it away. But sometimes "condition" never gives True for any value of "i" between imin and imax. In that case, my list turns to be {{}}, and Flatten does nothing.

I would like either {{}} to be a zero (but just in this case, as there are other zeros due to other reasons), or something able to tell Table to skip a step if "condition" is not satisfied.

Does anyone have any idea to deal with this?


Thanks in advance!

 

[Hepth]

Just do a :

If[Length[BLAH]==0,0,BLAH]

so if the length of that set is 0 it returns 0, else it returns the flattened set (where BLAH is the set)

 

[Gueygel]

Thanks Hepth! It wasn't very sophisticated in the end, I really appreciate it :)