I am trying to use such functions but I get a syntax error. In particular, this is my program, taken by the following book chapter:
https://ampl.com/BOOK/CHAPTERS/20-piecewise.pdf set ORIG; # origins set DEST; # destinations param supply {ORIG} >= 0; # amounts available at origins param demand {DEST} >= 0; # amounts required at destinations check: sum {i in ORIG} supply[i] = sum {j in DEST} demand[j]; param rate1 {i in ORIG, j in DEST} >= 0; param rate2 {i in ORIG, j in DEST} >= rate1[i,j]; param rate3 {i in ORIG, j in DEST} >= rate2[i,j]; param limit1 {i in ORIG, j in DEST} > 0; param limit2 {i in ORIG, j in DEST} > limit1[i,j]; var Trans {ORIG,DEST} >= 0; # units to be shipped minimize Total_Cost: sum {i in ORIG, j in DEST} <<limit1[i,j], limit2[i,j]; rate1[i,j], rate2[i,j], rate3[i,j]>> Trans[i,j]; subject to Supply {i in ORIG}: sum {j in DEST} Trans[i,j] = supply[i]; subject to Demand {j in DEST}: sum {i in ORIG} Trans[i,j] = demand[j]; When I try to make glpk parse it, I get the following error: glpsol --model glpk/Test --data /tmp/DATAg5ZQ0L -w /tmp/OUTXlm0ST GLPSOL: GLPK LP/MIP Solver, v4.61 Parameter(s) specified in the command line: --model glpk/Test --data /tmp/DATAg5ZQ0L -w /tmp/OUTXlm0ST Reading model section from glpk/Test... glpk/Test:14: syntax error in expression Context: ...>= 0 ; minimize Total_Cost : sum { i in ORIG , j in DEST } < MathProg model processing error I really have no clue as of now. Thanks
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