diff --git a/subprojects/cfa/src/main/java/hu/bme/mit/theta/cfa/dsl/CfaExpression.java b/subprojects/cfa/src/main/java/hu/bme/mit/theta/cfa/dsl/CfaExpression.java
index 57668124da..d08110dbfb 100644
--- a/subprojects/cfa/src/main/java/hu/bme/mit/theta/cfa/dsl/CfaExpression.java
+++ b/subprojects/cfa/src/main/java/hu/bme/mit/theta/cfa/dsl/CfaExpression.java
@@ -25,6 +25,7 @@
 import hu.bme.mit.theta.core.decl.Decl;
 import hu.bme.mit.theta.core.decl.ParamDecl;
 import hu.bme.mit.theta.core.dsl.DeclSymbol;
+import hu.bme.mit.theta.core.dsl.ParseException;
 import hu.bme.mit.theta.core.type.Expr;
 import hu.bme.mit.theta.core.type.Type;
 import hu.bme.mit.theta.core.type.abstracttype.*;
@@ -266,7 +267,7 @@ public Expr<?> visitEqualityExpr(final EqualityExprContext ctx) {
 					case NEQ:
 						return Neq(leftOp, rightOp);
 					default:
-						throw new AssertionError();
+						throw new ParseException(ctx, "Unknown operator");
 				}
 
 			} else {
@@ -290,7 +291,7 @@ public Expr<?> visitRelationExpr(final RelationExprContext ctx) {
 					case GEQ:
 						return Geq(leftOp, rightOp);
 					default:
-						throw new AssertionError();
+						throw new ParseException(ctx, "Unknown operator");
 				}
 
 			} else {
@@ -310,7 +311,7 @@ public Expr<?> visitBitwiseOrExpr(final BitwiseOrExprContext ctx) {
 					case BITWISE_OR:
 						return BvExprs.Or(List.of(leftOp, rightOp));
 					default:
-						throw new AssertionError();
+						throw new ParseException(ctx, "Unknown operator");
 				}
 
 			} else {
@@ -328,7 +329,7 @@ public Expr<?> visitBitwiseXorExpr(final BitwiseXorExprContext ctx) {
 					case BITWISE_XOR:
 						return BvExprs.Xor(List.of(leftOp, rightOp));
 					default:
-						throw new AssertionError();
+						throw new ParseException(ctx, "Unknown operator");
 				}
 
 			} else {
@@ -346,7 +347,7 @@ public Expr<?> visitBitwiseAndExpr(final BitwiseAndExprContext ctx) {
 					case BITWISE_AND:
 						return BvExprs.And(List.of(leftOp, rightOp));
 					default:
-						throw new AssertionError();
+						throw new ParseException(ctx, "Unknown operator");
 				}
 
 			} else {
@@ -372,7 +373,7 @@ public Expr<?> visitBitwiseShiftExpr(final BitwiseShiftExprContext ctx) {
 					case BITWISE_ROTATE_RIGHT:
 						return BvExprs.RotateRight(leftOp, rightOp);
 					default:
-						throw new AssertionError();
+						throw new ParseException(ctx, "Unknown operator");
 				}
 
 			} else {
@@ -391,14 +392,14 @@ public Expr<?> visitAdditiveExpr(final AdditiveExprContext ctx) {
 				final Expr<?> opsHead = ops.get(0);
 				final List<? extends Expr<?>> opsTail = ops.subList(1, ops.size());
 
-				return createAdditiveExpr(opsHead, opsTail, ctx.opers);
+				return createAdditiveExpr(opsHead, opsTail, ctx.opers, ctx);
 			} else {
 				return visitChildren(ctx);
 			}
 		}
 
 		private Expr<?> createAdditiveExpr(final Expr<?> opsHead, final List<? extends Expr<?>> opsTail,
-										   final List<? extends Token> opers) {
+										   final List<? extends Token> opers, final AdditiveExprContext ctx) {
 			checkArgument(opsTail.size() == opers.size());
 
 			if (opsTail.isEmpty()) {
@@ -410,13 +411,14 @@ private Expr<?> createAdditiveExpr(final Expr<?> opsHead, final List<? extends E
 				final Token operHead = opers.get(0);
 				final List<? extends Token> opersTail = opers.subList(1, opers.size());
 
-				final Expr<?> subExpr = createAdditiveSubExpr(opsHead, newOpsHead, operHead);
+				final Expr<?> subExpr = createAdditiveSubExpr(opsHead, newOpsHead, operHead, ctx);
 
-				return createAdditiveExpr(subExpr, newOpsTail, opersTail);
+				return createAdditiveExpr(subExpr, newOpsTail, opersTail, ctx);
 			}
 		}
 
-		private Expr<?> createAdditiveSubExpr(final Expr<?> leftOp, final Expr<?> rightOp, final Token oper) {
+		private Expr<?> createAdditiveSubExpr(final Expr<?> leftOp, final Expr<?> rightOp, final Token oper,
+											  final AdditiveExprContext ctx) {
 			switch (oper.getType()) {
 
 				case PLUS:
@@ -426,7 +428,7 @@ private Expr<?> createAdditiveSubExpr(final Expr<?> leftOp, final Expr<?> rightO
 					return createSubExpr(leftOp, rightOp);
 
 				default:
-					throw new AssertionError();
+					throw new ParseException(ctx, "Unknown operator '" + oper.getText() + "'");
 			}
 		}
 
@@ -456,7 +458,7 @@ public Expr<?> visitMultiplicativeExpr(final MultiplicativeExprContext ctx) {
 				final Expr<?> opsHead = ops.get(0);
 				final List<? extends Expr<?>> opsTail = ops.subList(1, ops.size());
 
-				return createMutliplicativeExpr(opsHead, opsTail, ctx.opers);
+				return createMutliplicativeExpr(opsHead, opsTail, ctx.opers, ctx);
 			} else {
 				return visitChildren(ctx);
 			}
@@ -464,7 +466,7 @@ public Expr<?> visitMultiplicativeExpr(final MultiplicativeExprContext ctx) {
 		}
 
 		private Expr<?> createMutliplicativeExpr(final Expr<?> opsHead, final List<? extends Expr<?>> opsTail,
-												 final List<? extends Token> opers) {
+												 final List<? extends Token> opers, final MultiplicativeExprContext ctx) {
 			checkArgument(opsTail.size() == opers.size());
 
 			if (opsTail.isEmpty()) {
@@ -476,13 +478,14 @@ private Expr<?> createMutliplicativeExpr(final Expr<?> opsHead, final List<? ext
 				final Token operHead = opers.get(0);
 				final List<? extends Token> opersTail = opers.subList(1, opers.size());
 
-				final Expr<?> subExpr = createMultiplicativeSubExpr(opsHead, newOpsHead, operHead);
+				final Expr<?> subExpr = createMultiplicativeSubExpr(opsHead, newOpsHead, operHead, ctx);
 
-				return createMutliplicativeExpr(subExpr, newOpsTail, opersTail);
+				return createMutliplicativeExpr(subExpr, newOpsTail, opersTail, ctx);
 			}
 		}
 
-		private Expr<?> createMultiplicativeSubExpr(final Expr<?> leftOp, final Expr<?> rightOp, final Token oper) {
+		private Expr<?> createMultiplicativeSubExpr(final Expr<?> leftOp, final Expr<?> rightOp, final Token oper,
+													final MultiplicativeExprContext ctx) {
 			switch (oper.getType()) {
 
 				case MUL:
@@ -498,7 +501,7 @@ private Expr<?> createMultiplicativeSubExpr(final Expr<?> leftOp, final Expr<?>
 					return createRemExpr(leftOp, rightOp);
 
 				default:
-					throw new AssertionError();
+					throw new ParseException(ctx, "Unknown operator '" + oper.getText() + "'");
 			}
 		}
 
@@ -539,7 +542,7 @@ public Expr<?> visitUnaryExpr(final UnaryExprContext ctx) {
 						return Neg(op);
 
 					default:
-						throw new AssertionError();
+						throw new ParseException(ctx, "Unknown operator");
 				}
 			} else {
 				return visitChildren(ctx);
@@ -588,7 +591,7 @@ private Expr<?> createAccessSubExpr(final Expr<?> op, final AccessContext access
 			} else if (access.prime != null) {
 				return createPrimeExpr(op);
 			} else {
-				throw new AssertionError();
+				throw new ParseException(access, "Unknown expression");
 			}
 		}
 
@@ -723,7 +726,7 @@ else if(sizeAndContent[1].startsWith("x")) {
 				isSigned = false;
 			}
 			else {
-				throw new IllegalArgumentException("Invalid bitvector literal");
+				throw new ParseException(ctx, "Invalid bitvector literal");
 			}
 
 			checkArgument(value.length <= size, "The value of the literal cannot be represented on the given amount of bits");
@@ -801,8 +804,7 @@ private boolean[] decodeHexadecimalBvContent(String lit) {
 		public RefExpr<?> visitIdExpr(final IdExprContext ctx) {
 			Optional<? extends Symbol> optSymbol = currentScope.resolve(ctx.id.getText());
 			if (optSymbol.isEmpty()) {
-				throw new NoSuchElementException("Identifier '" + ctx.id.getText() + "' at line " +
-						ctx.start.getLine() + " cannot be resolved");
+				throw new ParseException(ctx, "Identifier '" + ctx.id.getText() + "' cannot be resolved");
 			}
 			final Symbol symbol = optSymbol.get();
 			final Decl<?> decl = (Decl<?>) env.eval(symbol);
diff --git a/subprojects/core/src/main/java/hu/bme/mit/theta/core/dsl/ParseException.java b/subprojects/core/src/main/java/hu/bme/mit/theta/core/dsl/ParseException.java
new file mode 100644
index 0000000000..cfb141feec
--- /dev/null
+++ b/subprojects/core/src/main/java/hu/bme/mit/theta/core/dsl/ParseException.java
@@ -0,0 +1,29 @@
+/*
+ *  Copyright 2017 Budapest University of Technology and Economics
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package hu.bme.mit.theta.core.dsl;
+
+import org.antlr.v4.runtime.ParserRuleContext;
+
+public class ParseException extends RuntimeException {
+	public ParseException(ParserRuleContext ctx, String message){
+		this(ctx, message, null);
+	}
+
+	public ParseException(ParserRuleContext ctx, String message, Throwable cause) {
+		super("Line " + ctx.getStart().getLine() + " col " + ctx.getStart().getCharPositionInLine() + ": " + message, cause);
+	}
+
+}
diff --git a/subprojects/sts/src/main/java/hu/bme/mit/theta/sts/dsl/StsExprCreatorVisitor.java b/subprojects/sts/src/main/java/hu/bme/mit/theta/sts/dsl/StsExprCreatorVisitor.java
index 3d59cddd25..e346abcf70 100644
--- a/subprojects/sts/src/main/java/hu/bme/mit/theta/sts/dsl/StsExprCreatorVisitor.java
+++ b/subprojects/sts/src/main/java/hu/bme/mit/theta/sts/dsl/StsExprCreatorVisitor.java
@@ -48,6 +48,7 @@
 import java.util.Optional;
 import java.util.stream.Stream;
 
+import hu.bme.mit.theta.core.dsl.ParseException;
 import org.antlr.v4.runtime.Token;
 
 import com.google.common.collect.ImmutableList;
@@ -268,7 +269,7 @@ public Expr<?> visitEqualityExpr(final EqualityExprContext ctx) {
 				case StsDslParser.NEQ:
 					return Neq(leftOp, rightOp);
 				default:
-					throw new AssertionError();
+					throw new ParseException(ctx, "Unknown operator");
 			}
 
 		} else {
@@ -292,7 +293,7 @@ public Expr<?> visitRelationExpr(final RelationExprContext ctx) {
 				case StsDslParser.GEQ:
 					return Geq(leftOp, rightOp);
 				default:
-					throw new AssertionError();
+					throw new ParseException(ctx, "Unknown operator");
 			}
 
 		} else {
@@ -311,14 +312,14 @@ public Expr<?> visitAdditiveExpr(final AdditiveExprContext ctx) {
 			final Expr<?> opsHead = ops.get(0);
 			final List<? extends Expr<?>> opsTail = ops.subList(1, ops.size());
 
-			return createAdditiveExpr(opsHead, opsTail, ctx.opers);
+			return createAdditiveExpr(opsHead, opsTail, ctx.opers, ctx);
 		} else {
 			return visitChildren(ctx);
 		}
 	}
 
 	private Expr<?> createAdditiveExpr(final Expr<?> opsHead, final List<? extends Expr<?>> opsTail,
-									   final List<? extends Token> opers) {
+									   final List<? extends Token> opers, final AdditiveExprContext ctx) {
 		checkArgument(opsTail.size() == opers.size());
 
 		if (opsTail.isEmpty()) {
@@ -330,13 +331,14 @@ private Expr<?> createAdditiveExpr(final Expr<?> opsHead, final List<? extends E
 			final Token operHead = opers.get(0);
 			final List<? extends Token> opersTail = opers.subList(1, opers.size());
 
-			final Expr<?> subExpr = createAdditiveSubExpr(opsHead, newOpsHead, operHead);
+			final Expr<?> subExpr = createAdditiveSubExpr(opsHead, newOpsHead, operHead, ctx);
 
-			return createAdditiveExpr(subExpr, newOpsTail, opersTail);
+			return createAdditiveExpr(subExpr, newOpsTail, opersTail, ctx);
 		}
 	}
 
-	private Expr<?> createAdditiveSubExpr(final Expr<?> leftOp, final Expr<?> rightOp, final Token oper) {
+	private Expr<?> createAdditiveSubExpr(final Expr<?> leftOp, final Expr<?> rightOp, final Token oper,
+										  final AdditiveExprContext ctx) {
 		switch (oper.getType()) {
 
 			case StsDslParser.PLUS:
@@ -346,7 +348,7 @@ private Expr<?> createAdditiveSubExpr(final Expr<?> leftOp, final Expr<?> rightO
 				return createSubExpr(leftOp, rightOp);
 
 			default:
-				throw new AssertionError();
+				throw new ParseException(ctx, "Unknown operator '" + oper.getText() + "'");
 		}
 	}
 
@@ -375,7 +377,7 @@ public Expr<?> visitMultiplicativeExpr(final MultiplicativeExprContext ctx) {
 			final Expr<?> opsHead = ops.get(0);
 			final List<? extends Expr<?>> opsTail = ops.subList(1, ops.size());
 
-			return createMutliplicativeExpr(opsHead, opsTail, ctx.opers);
+			return createMutliplicativeExpr(opsHead, opsTail, ctx.opers, ctx);
 		} else {
 			return visitChildren(ctx);
 		}
@@ -383,7 +385,7 @@ public Expr<?> visitMultiplicativeExpr(final MultiplicativeExprContext ctx) {
 	}
 
 	private Expr<?> createMutliplicativeExpr(final Expr<?> opsHead, final List<? extends Expr<?>> opsTail,
-											 final List<? extends Token> opers) {
+											 final List<? extends Token> opers, final MultiplicativeExprContext ctx) {
 		checkArgument(opsTail.size() == opers.size());
 
 		if (opsTail.isEmpty()) {
@@ -395,13 +397,14 @@ private Expr<?> createMutliplicativeExpr(final Expr<?> opsHead, final List<? ext
 			final Token operHead = opers.get(0);
 			final List<? extends Token> opersTail = opers.subList(1, opers.size());
 
-			final Expr<?> subExpr = createMultiplicativeSubExpr(opsHead, newOpsHead, operHead);
+			final Expr<?> subExpr = createMultiplicativeSubExpr(opsHead, newOpsHead, operHead, ctx);
 
-			return createMutliplicativeExpr(subExpr, newOpsTail, opersTail);
+			return createMutliplicativeExpr(subExpr, newOpsTail, opersTail, ctx);
 		}
 	}
 
-	private Expr<?> createMultiplicativeSubExpr(final Expr<?> leftOp, final Expr<?> rightOp, final Token oper) {
+	private Expr<?> createMultiplicativeSubExpr(final Expr<?> leftOp, final Expr<?> rightOp, final Token oper,
+												final MultiplicativeExprContext ctx) {
 		switch (oper.getType()) {
 
 			case StsDslParser.MUL:
@@ -417,7 +420,7 @@ private Expr<?> createMultiplicativeSubExpr(final Expr<?> leftOp, final Expr<?>
 				return createRemExpr(leftOp, rightOp);
 
 			default:
-				throw new AssertionError();
+				throw new ParseException(ctx, "Unknown operator '" + oper.getText() + "'");
 		}
 	}
 
@@ -489,18 +492,16 @@ private Expr<?> createAccessSubExpr(final Expr<?> op, final AccessContext access
 		} else if (access.prime != null) {
 			return createPrimeExpr(op);
 		} else {
-			throw new AssertionError();
+			throw new ParseException(access, "Unknown expression");
 		}
 	}
 
 	private Expr<?> createFuncAppExpr(final Expr<?> op, final FuncAccessContext ctx) {
-		// TODO Auto-generated method stub
-		throw new UnsupportedOperationException("TODO: auto-generated method stub");
+		throw new ParseException(ctx, "Unsupported expression");
 	}
 
 	private Expr<?> createArrayReadExpr(final Expr<?> op, final ArrayAccessContext ctx) {
-		// TODO Auto-generated method stub
-		throw new UnsupportedOperationException("TODO: auto-generated method stub");
+		throw new ParseException(ctx, "Unsupported expression");
 	}
 
 	private Expr<?> createPrimeExpr(final Expr<?> op) {
@@ -536,7 +537,9 @@ public RatLitExpr visitRatLitExpr(final RatLitExprContext ctx) {
 	public Expr<?> visitIdExpr(final IdExprContext ctx) {
 		final Optional<? extends Symbol> optSymbol = currentScope.resolve(ctx.id.getText());
 
-		if (optSymbol.isEmpty()) throw new NoSuchElementException("Identifier '" + ctx.id.getText() + "' not found");
+		if (optSymbol.isEmpty()) {
+			throw new ParseException(ctx, "Identifier '" + ctx.id.getText() + "' cannot be resolved");
+		}
 		final Symbol symbol = optSymbol.get();
 
 		checkArgument(symbol instanceof DeclSymbol);
diff --git a/subprojects/xsts/src/main/java/hu/bme/mit/theta/xsts/dsl/XSTSVisitor.java b/subprojects/xsts/src/main/java/hu/bme/mit/theta/xsts/dsl/XSTSVisitor.java
index 5c8d11fac6..f20314e270 100644
--- a/subprojects/xsts/src/main/java/hu/bme/mit/theta/xsts/dsl/XSTSVisitor.java
+++ b/subprojects/xsts/src/main/java/hu/bme/mit/theta/xsts/dsl/XSTSVisitor.java
@@ -2,6 +2,7 @@
 
 import hu.bme.mit.theta.core.decl.Decls;
 import hu.bme.mit.theta.core.decl.VarDecl;
+import hu.bme.mit.theta.core.dsl.ParseException;
 import hu.bme.mit.theta.core.stmt.*;
 import hu.bme.mit.theta.core.type.Expr;
 import hu.bme.mit.theta.core.type.booltype.BoolType;
@@ -66,12 +67,14 @@ private void checkIfTempVar(String name){
     @Override
     public Expr visitTypeDeclaration(XstsDslParser.TypeDeclarationContext ctx) {
         checkIfTempVar(ctx.name.getText());
-        if(nameToTypeMap.containsKey(ctx.name.getText()) || ctx.name.getText().equals("integer") || ctx.name.getText().equals("boolean")) throw new RuntimeException("Type "+ctx.name.getText()+" already exists!"+" On line "+ctx.start.getLine());
+        if(nameToTypeMap.containsKey(ctx.name.getText()) || ctx.name.getText().equals("integer") || ctx.name.getText().equals("boolean")) {
+            throw new ParseException(ctx, "Type '" + ctx.name.getText() + "' already exists!");
+        }
         List<String> literals=new ArrayList<>();
         List<BigInteger> intValues=new ArrayList<>();
         for(XstsDslParser.TypeLiteralContext literal:ctx.literals){
             checkIfTempVar(literal.name.getText());
-            if(literals.contains(literal.name.getText())) throw new RuntimeException("Duplicate literal "+literal.name.getText()+" in type "+ctx.name.getText());
+            if(literals.contains(literal.name.getText())) throw new ParseException(ctx, "Duplicate literal '" + literal.name.getText() + "' in type '" + ctx.name.getText() + "'");
             if(literalToIntMap.containsKey(literal.name.getText())) {
                 intValues.add(literalToIntMap.get(literal.name.getText()));
             } else {
@@ -90,9 +93,9 @@ public Expr visitTypeDeclaration(XstsDslParser.TypeDeclarationContext ctx) {
     public Expr visitVariableDeclaration(XstsDslParser.VariableDeclarationContext ctx) {
         checkIfTempVar(ctx.name.getText());
         if(nameToDeclMap.containsKey(ctx.name.getText())){
-            throw new RuntimeException("Variable ["+ctx.name.getText()+"] already exists.");
+            throw new ParseException(ctx, "Variable '" + ctx.name.getText() + "' already exists.");
         } else if(literalToIntMap.containsKey(ctx.name.getText())){
-            throw new RuntimeException("["+ctx.name.getText()+"] is a type literal, cannot declare variable with this name.");
+            throw new ParseException(ctx, "'" + ctx.name.getText() + "' is a type literal, cannot declare variable with this name.");
         }
 
         VarDecl decl;
@@ -106,7 +109,7 @@ else if(nameToTypeMap.containsKey(ctx.type.customType().name.getText())){
             decl=Decls.Var(ctx.name.getText(),IntType.getInstance());
             varToTypeMap.put(decl,nameToTypeMap.get(ctx.type.customType().name.getText()));
         } else {
-            throw new RuntimeException("Unknown type "+ctx.type.customType().name.getText()+" on line "+ctx.start.getLine());
+            throw new ParseException(ctx, "Unknown type '" + ctx.type.customType().name.getText() + "'.");
         }
 
         if(ctx.CTRL()!=null) ctrlVars.add(decl);
@@ -119,17 +122,17 @@ else if(nameToTypeMap.containsKey(ctx.type.customType().name.getText())){
 
     @Override
     public Expr visitExpr(XstsDslParser.ExprContext ctx) {
-        if(ctx.iteExpression()==null) throw new RuntimeException("Invalid expression on line "+ctx.start.getLine());
+        if (ctx.iteExpression() == null) throw new ParseException(ctx, "Invalid expression.");
         return visitIteExpression(ctx.iteExpression());
     }
 
     @Override
     public Expr visitIteExpression(XstsDslParser.IteExpressionContext ctx) {
-        if(ctx.cond != null){
-            if(ctx.then == null || ctx.elze == null) throw new RuntimeException("Invalid if-then-else expression on line "+ctx.start.getLine());
-            return Ite(visitExpr(ctx.cond),visitExpr(ctx.then),visitExpr(ctx.elze));
+        if (ctx.cond != null){
+            if (ctx.then == null || ctx.elze == null) throw new ParseException(ctx, "Invalid if-then-else expression.");
+            return Ite(visitExpr(ctx.cond), visitExpr(ctx.then), visitExpr(ctx.elze));
         } else {
-            if(ctx.implyExpression()==null) throw new RuntimeException("Invalid expression on line "+ctx.start.getLine());
+            if (ctx.implyExpression() == null) throw new ParseException(ctx, "Invalid expression.");
             return visitImplyExpression(ctx.implyExpression());
         }
     }
@@ -191,7 +194,7 @@ public Expr visitRelationExpr(XstsDslParser.RelationExprContext ctx) {
                 return Lt(visitAdditiveExpr(ctx.ops.get(0)),visitAdditiveExpr(ctx.ops.get(1)));
             }else if(ctx.oper.GT()!=null){
                 return Gt(visitAdditiveExpr(ctx.ops.get(0)),visitAdditiveExpr(ctx.ops.get(1)));
-            } else throw new UnsupportedOperationException("Unsupported operation "+ctx.oper.getText()+" on line "+ctx.start.getLine());
+            } else throw new ParseException(ctx, "Unsupported operation '" + ctx.oper.getText() + "'");
         }else return visitAdditiveExpr(ctx.ops.get(0));
     }
 
@@ -230,7 +233,7 @@ public Expr visitMultiplicativeExpr(XstsDslParser.MultiplicativeExprContext ctx)
             }else if(ctx.opers.get(i-1).MUL()!=null){
                 res=Mul(res,visitNegExpr(ctx.ops.get(i)));
             } else{
-                throw new UnsupportedOperationException("Unsupported operation "+ctx.opers.get(i-1).getText()+" on line "+ctx.start.getLine());
+                throw new ParseException(ctx, "Unsupported operation '" + ctx.opers.get(i-1).getText() + "'");
             }
         }
         return res;
@@ -272,7 +275,7 @@ public Expr visitLiteral(XstsDslParser.LiteralContext ctx) {
             if(ctx.BOOLLIT().getText().equals("true")) return True(); else return False();
         }else if(ctx.INTLIT()!=null){
             return Int(ctx.INTLIT().getText());
-        }else throw new RuntimeException("Literal "+ctx.getText()+" could not be resolved to integer or boolean type."+" On line "+ctx.start.getLine());
+        }else throw new ParseException(ctx, "Literal '" + ctx.getText() + "' could not be resolved to integer or boolean type.");
     }
 
     @Override
@@ -280,15 +283,14 @@ public Expr visitReference(XstsDslParser.ReferenceContext ctx) {
         checkIfTempVar(ctx.name.getText());
         if(literalToIntMap.containsKey(ctx.name.getText())) return Int(literalToIntMap.get(ctx.name.getText()));
         else if(nameToDeclMap.containsKey(ctx.name.getText())) return nameToDeclMap.get(ctx.name.getText()).getRef();
-        else throw new RuntimeException("Literal or reference "+ctx.name.getText()+" could not be resolved."+" On line "+ctx.start.getLine());
+        else throw new ParseException(ctx, "Literal or reference '" + ctx.name.getText() + "' could not be resolved.");
 
     }
 
     @Override
     public Expr visitPrime(XstsDslParser.PrimeContext ctx) {
         if(ctx.reference()!=null) return visitReference(ctx.reference());
-        else throw new UnsupportedOperationException("Prime expressions are not supported."+" On line "+ctx.start.getLine());
-//            return Prime(visitPrime(ctx.prime()));
+        else throw new ParseException(ctx, "Prime expressions are not supported.");
     }
 
     public Stmt processAction(XstsDslParser.ActionContext ctx) {
@@ -329,12 +331,16 @@ public AssumeStmt processAssumeAction(XstsDslParser.AssumeActionContext ctx) {
     }
 
     public AssignStmt processAssignAction(XstsDslParser.AssignActionContext ctx) {
-        if(!nameToDeclMap.containsKey(ctx.lhs.getText())) throw new RuntimeException("Could not resolve variable "+ctx.lhs.getText()+" on line "+ctx.start.getLine());
+        if(!nameToDeclMap.containsKey(ctx.lhs.getText())) {
+            throw new ParseException(ctx, "Could not resolve variable '" + ctx.lhs.getText() + "'");
+        }
         return Stmts.Assign(nameToDeclMap.get(ctx.lhs.getText()),visitExpr(ctx.rhs));
     }
 
     public HavocStmt processHavocAction(XstsDslParser.HavocActionContext ctx){
-        if(!nameToDeclMap.containsKey(ctx.name.getText())) throw new RuntimeException("Could not resolve variable "+ctx.name.getText()+" on line "+ctx.start.getLine());
+        if(!nameToDeclMap.containsKey(ctx.name.getText())) {
+            throw new ParseException(ctx, "Could not resolve variable '" + ctx.name.getText() + "'");
+        }
         return Stmts.Havoc(nameToDeclMap.get(ctx.name.getText()));
     }
 }