[Bug-glpk] 0-ary slice not allowed

[xypron]

Hello Andrew,

constraint

s.t. cost {i in N, j in N} :
  t[i] - t[j] - sum{(i,j) in E} c[i,j] * x[i,j] >= 0;

leads to error

0-ary slice not allowed

in glpmpl01.c, function expression_list.

My expectation was that the sum is 0 if (i,j) is not an element of E and
c[i,j] x[i,j] otherwise. This would be in conformance with the usual use of
domain parameters.

I must admit that the following is an alternative notation but less elegant:

s.t. cost {i in N, j in N } :
  t[i] - t[j] -  ( if ((i,j) in E) then c[i,j] * x[i,j] else 0 ) >= 0;

Best regards

Xypron

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