fix bugs with cbrt

- it was not handled in the model block
- output was incorrect for MATLAB/Octave and LaTeX

src/DynareBison.yy

@@ -1014,6 +1014,8 @@ hand_side : '(' hand_side ')'
             { $$ = driver.add_atan($3); }
           | SQRT '(' hand_side ')'
             { $$ = driver.add_sqrt($3); }
+          | CBRT '(' hand_side ')'
+             { $$ = driver.add_cbrt($3); }
           | ABS '(' hand_side ')'
             { $$ = driver.add_abs($3); }
           | SIGN '(' hand_side ')'

src/ExprNode.cc

@@ -2777,7 +2777,22 @@ UnaryOpNode::writeOutput(ostream &output, ExprNodeOutputType output_type,
       output << "sqrt";
       break;
     case UnaryOpcode::cbrt:
-      output << "cbrt";
+      if (isMatlabOutput(output_type))
+        {
+          output << "nthroot(";
+          arg->writeOutput(output, output_type, temporary_terms, temporary_terms_idxs, tef_terms);
+          output << ", 3)";
+          return;
+        }
+      else if (isLatexOutput(output_type))
+        {
+          output << R"(\sqrt[3]{)";
+          arg->writeOutput(output, output_type, temporary_terms, temporary_terms_idxs, tef_terms);
+          output << "}";
+          return;
+        }
+      else
+        output << "cbrt";
       break;
     case UnaryOpcode::abs:
       output << "abs";