Merge branch 'hdavid16:master' into master

Author: shivankj11

src/big_M.jl

@@ -1,13 +1,15 @@
 function big_m_reformulation!(constr, bin_var, i, k, M)
     if ismissing(k)
         ref = constr
+    elseif k isa CartesianIndex
+        ref = constr[k]
     else
         ref = constr[k...]
     end
     if ismissing(M)
         M = apply_interval_arithmetic(ref)
         # @warn "No M value passed for $ref. M = $M was inferred from the variable bounds."
-    elseif !ismissing(k)
+    elseif !ismissing(k) && !isa(M,Real)
         M = M[k]
     end
     if ref isa NonlinearConstraintRef

src/utils.jl

@@ -150,8 +150,9 @@ end
 
 function replace_intevals!(expr, intervals)
     #replace variables with their intervals
-    if string(expr) in keys(intervals) #check if expression is one of the model variables in the intervals dict
-        return intervals[string(expr)] #replace expression with interval
+    expr_str = replace(string(expr), ", " => ",") #remove any blank space after index commas
+    if expr_str in keys(intervals) #check if expression is one of the model variables in the intervals dict
+        return intervals[expr_str] #replace expression with interval
     elseif expr isa Expr
         if length(expr.args) == 1 #run recursive relation on the leaf node on expression tree
             expr.args[i] = replace_intevals!(expr.args[i], intervals)