Fix error for printing in IJuliaMode

src/print.jl

@@ -617,12 +617,37 @@ end
 #------------------------------------------------------------------------
 ## _NonlinearExprData
 #------------------------------------------------------------------------
-function nl_expr_string(model::Model, mode, c::_NonlinearExprData)
-    return string(_tape_to_expr(model, 1, c.nd, adjmat(c.nd), c.const_values,
-                                [], [], model.nlp_data.user_operators, false,
-                                false, mode))
+function nl_expr_string(model::Model, print_mode, c::_NonlinearExprData)
+    ex = _tape_to_expr(model, 1, c.nd, adjmat(c.nd), c.const_values,
+                       [], [], model.nlp_data.user_operators, false,
+                       false, print_mode)
+    if print_mode == IJuliaMode
+        ex = _latexify_exponentials(ex)
+    end
+    return string(ex)
+end
+
+# Change x ^ -2.0 to x ^ {-2.0}
+# x ^ (x ^ 2.0) to x ^ {x ^ {2.0}}
+# and so on
+function _latexify_exponentials(ex::Expr)
+    if ex.head != :call
+        return ex
+    end
+    for i = 1:length(ex.args)
+        if isa(ex.args[i], Expr)
+            ex.args[i] = _latexify_exponentials(ex.args[i])
+        end
+        if ex.args[1] == :^
+            if isa(ex.args[3], Expr)
+                ex.args[3] = _latexify_exponentials(ex.args[3])
+            end
+            ex.args[3] = Expr(:braces, ex.args[3])
+            return ex
+        end
+    end
+    return ex
 end
-
 #------------------------------------------------------------------------
 ## _NonlinearConstraint
 #------------------------------------------------------------------------

test/print.jl

@@ -197,18 +197,42 @@ end
         constr_ge = @NLconstraint(model, sin(x) >= 1)
         constr_eq = @NLconstraint(model, sin(x) == 1)
         constr_range = @NLconstraint(model, 0 <= sin(x) <= 1)
+        constr_exponent_1 = @NLconstraint(model, x^4 <= 1)
+        constr_exponent_2 = @NLconstraint(model, x^40.23 <= 1)
+        constr_exponent_3 = @NLconstraint(model, x^4 + x^3 + x^2 <= 1)
+        constr_exponent_4 = @NLconstraint(model, x^-4 + x^-3 + x^-2 <= 1)
+        constr_exponent_5 = @NLconstraint(model, x^(x * x) <= 1)
+        constr_exponent_6 = @NLconstraint(model, x^(2x) <= 1)
+        constr_exponent_7 = @NLconstraint(model, x^(2 * 5) <= 1)
+        constr_exponent_8 = @NLconstraint(model, x^(x^2) <= 1)
 
         io_test(REPLMode, constr_le, "sin(x) - 1.0 $le 0")
         io_test(REPLMode, constr_ge, "sin(x) - 1.0 $ge 0")
         io_test(REPLMode, constr_eq, "sin(x) - 1.0 $eq 0")
         # Note: This is inconsistent with the "x in [-1, 1]" printing for
         # regular constraints.
         io_test(REPLMode, constr_range, "0 $le sin(x) $le 1")
+        io_test(REPLMode, constr_exponent_1, "x ^ 4.0 - 1.0 $le 0")
+        io_test(REPLMode, constr_exponent_2, "x ^ 40.23 - 1.0 $le 0")
+        io_test(REPLMode, constr_exponent_3, "(x ^ 4.0 + x ^ 3.0 + x ^ 2.0) - 1.0 $le 0")
+        io_test(REPLMode, constr_exponent_4, "(x ^ -4.0 + x ^ -3.0 + x ^ -2.0) - 1.0 $le 0")
+        io_test(REPLMode, constr_exponent_5, "x ^ (x * x) - 1.0 $le 0")
+        io_test(REPLMode, constr_exponent_6, "x ^ (2.0 * x) - 1.0 $le 0")
+        io_test(REPLMode, constr_exponent_7, "x ^ (2.0 * 5.0) - 1.0 $le 0")
+        io_test(REPLMode, constr_exponent_8, "x ^ (x ^ 2.0) - 1.0 $le 0")
 
         io_test(IJuliaMode, constr_le, "sin(x) - 1.0 \\leq 0")
         io_test(IJuliaMode, constr_ge, "sin(x) - 1.0 \\geq 0")
         io_test(IJuliaMode, constr_eq, "sin(x) - 1.0 = 0")
         io_test(IJuliaMode, constr_range, "0 \\leq sin(x) \\leq 1")
+        io_test(IJuliaMode, constr_exponent_1, "x ^ {4.0} - 1.0 \\leq 0")
+        io_test(IJuliaMode, constr_exponent_2, "x ^ {40.23} - 1.0 \\leq 0")
+        io_test(IJuliaMode, constr_exponent_3, "(x ^ {4.0} + x ^ {3.0} + x ^ {2.0}) - 1.0 \\leq 0")
+        io_test(IJuliaMode, constr_exponent_4, "(x ^ {-4.0} + x ^ {-3.0} + x ^ {-2.0}) - 1.0 \\leq 0")
+        io_test(IJuliaMode, constr_exponent_5, "x ^ {x * x} - 1.0 \\leq 0")
+        io_test(IJuliaMode, constr_exponent_6, "x ^ {2.0 * x} - 1.0 \\leq 0")
+        io_test(IJuliaMode, constr_exponent_7, "x ^ {2.0 * 5.0} - 1.0 \\leq 0")
+        io_test(IJuliaMode, constr_exponent_8, "x ^ {x ^ {2.0}} - 1.0 \\leq 0")
     end
 
     @testset "Nonlinear constraints with embedded parameters/expressions" begin