Reorganize package; add macros

src/problems/knapsack.jl

@@ -0,0 +1,25 @@
+#  MIPLearn: Extensible Framework for Learning-Enhanced Mixed-Integer Optimization
+#  Copyright (C) 2020-2021, UChicago Argonne, LLC. All rights reserved.
+#  Released under the modified BSD license. See COPYING.md for more details.
+
+using JuMP
+
+function knapsack_model(
+    weights::Array{Float64, 1},
+    prices::Array{Float64, 1},
+    capacity::Float64,
+)
+    model = Model()
+    n = length(weights)
+    @variable(model, x[0:(n-1)], Bin)
+    @objective(model, Max, sum(x[i] * prices[i+1] for i in 0:(n-1)))
+    @constraint(
+        model,
+        eq_capacity,
+        sum(
+            x[i] * weights[i+1]
+            for i in 0:(n-1)
+        ) <= capacity,
+    )
+    return model
+end