[AMPL 24974] A syntax error in a constraint loop

Google Group Mirror
1

Hi,
Recently I have this syntax error in one of my constraints

syntax error
context: subject to precedence_in_part_platform {j in J, l >>> in <<< J: l<>j} : 1 + x[j] >= f[j,l] + x[l];
ampl:

The model was working fine las month. I do not know the reason for this error, given that the model have earlier constraints with this loop but it did not give any syntax error.

Could you please help, Thanks a lot

2

Did you define l as a param or var earlier in the model? If l is already defined, then writing l in J in the constraint indexing gives exactly the error you are seeing. For example:

ampl: param l; set J; var x{J}; var f{J,J};
ampl: subject to precedence_in_part_platform {j in J, l in J: l<>j} : 1 + x[j] >= f[j,l] + x[l];

syntax error
context:  subject to precedence_in_part_platform {j in J, l  >>> in  <<< J: l<>j} : 1 + x[j] >= f[j,l] + x[l];
ampl:

If you aren’t defining l earlier in the model, then can you post an example from your model, which causes the error to appear?

3

Your question has been moved to our new user forum at discuss.ampl.com, and a reply has been posted. To see the reply, go here:

https://discuss.ampl.com/t/ampl-24974-a-syntax-error-in-a-constraint-loop/925

4

Thanks a lot, it is solved