From a21eb396b9f923daa717c916b8e1fbf904eb28ac Mon Sep 17 00:00:00 2001
From: villberg <villberg@ac1ea38d-2e2b-0410-8846-a27921b304fc>
Date: Mon, 31 Mar 2014 11:16:46 +0000
Subject: [PATCH] Getting closer refs #4765

git-svn-id: https://www.simantics.org/svn/simantics/sysdyn/trunk@29221 ac1ea38d-2e2b-0410-8846-a27921b304fc
---
 .../META-INF/MANIFEST.MF                      |  3 +-
 .../fi/semantum/sysdyn/solver/Addition.java   |  7 ++
 .../src/fi/semantum/sysdyn/solver/And.java    |  8 ++
 .../semantum/sysdyn/solver/Application.java   |  9 +++
 .../fi/semantum/sysdyn/solver/Argument.java   |  8 ++
 .../src/fi/semantum/sysdyn/solver/Array.java  | 12 +++
 .../sysdyn/solver/ArraySliceExpression.java   |  9 +++
 .../fi/semantum/sysdyn/solver/Assignment.java |  2 +-
 .../fi/semantum/sysdyn/solver/Constant.java   |  7 ++
 .../semantum/sysdyn/solver/Declaration.java   |  8 ++
 .../fi/semantum/sysdyn/solver/Derivate.java   | 14 +++-
 .../fi/semantum/sysdyn/solver/Derivative.java |  5 ++
 .../fi/semantum/sysdyn/solver/Division.java   |  9 +++
 .../sysdyn/solver/ElementwiseProduct.java     |  9 +++
 .../src/fi/semantum/sysdyn/solver/Equals.java |  9 +++
 .../fi/semantum/sysdyn/solver/ForArray.java   | 13 +++
 .../sysdyn/solver/GreaterOrEqualThan.java     |  9 +++
 .../semantum/sysdyn/solver/GreaterThan.java   |  9 +++
 .../semantum/sysdyn/solver/IExpression.java   |  5 ++
 .../fi/semantum/sysdyn/solver/IfThenElse.java | 10 +++
 .../sysdyn/solver/LessOrEqualThan.java        |  9 +++
 .../fi/semantum/sysdyn/solver/LessThan.java   |  9 +++
 .../sysdyn/solver/Multiplication.java         |  9 +++
 .../fi/semantum/sysdyn/solver/Negation.java   |  8 ++
 .../fi/semantum/sysdyn/solver/NotEquals.java  |  9 +++
 .../sysdyn/solver/NullModification.java       |  5 ++
 .../src/fi/semantum/sysdyn/solver/Or.java     |  8 ++
 .../sysdyn/solver/ParameterDeclaration.java   |  5 ++
 .../src/fi/semantum/sysdyn/solver/Solver.java | 80 ++++++++++++++++---
 .../semantum/sysdyn/solver/Subtraction.java   |  9 +++
 .../semantum/sysdyn/solver/TimeVariable.java  |  7 ++
 .../fi/semantum/sysdyn/solver/Variable.java   |  7 ++
 .../semantum/sysdyn/solver/VariableBase.java  |  2 -
 .../sysdyn/solver/VariableDeclaration.java    |  7 ++
 34 files changed, 325 insertions(+), 14 deletions(-)

diff --git a/fi.semantum.sysdyn.solver/META-INF/MANIFEST.MF b/fi.semantum.sysdyn.solver/META-INF/MANIFEST.MF
index 7f8fe97d..3256e513 100644
--- a/fi.semantum.sysdyn.solver/META-INF/MANIFEST.MF
+++ b/fi.semantum.sysdyn.solver/META-INF/MANIFEST.MF
@@ -7,7 +7,8 @@ Bundle-Activator: fi.semantum.sysdyn.solver.Activator
 Bundle-Vendor: Semantum Oy
 Require-Bundle: org.eclipse.core.runtime,
  org.simantics.utils;bundle-version="1.1.0",
- org.simantics.databoard;bundle-version="0.6.5"
+ org.simantics.databoard;bundle-version="0.6.5",
+ org.simantics.utils.datastructures;bundle-version="1.1.0"
 Bundle-RequiredExecutionEnvironment: JavaSE-1.6
 Bundle-ActivationPolicy: lazy
 Export-Package: fi.semantum.sysdyn.solver
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Addition.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Addition.java
index 27ee6841..a407ca4e 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Addition.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Addition.java
@@ -61,4 +61,11 @@ public class Addition implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		exp1.accept(visitor);
+		exp2.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/And.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/And.java
index d77a191c..dc3ab53d 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/And.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/And.java
@@ -13,6 +13,8 @@ package fi.semantum.sysdyn.solver;
 import java.util.ArrayList;
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class And implements IExpression {
 	
     public IExpression[] exps;
@@ -59,4 +61,10 @@ public class And implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		for(IExpression exp : exps) exp.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Application.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Application.java
index c9c2282c..a59ece28 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Application.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Application.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class Application implements IExpression {
 
 	public String name;
@@ -48,4 +50,11 @@ public class Application implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		for(Argument a : args.args)
+			a.modification.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Argument.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Argument.java
index 3a7013f4..2712ab90 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Argument.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Argument.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class Argument implements IExpression {
 
 	public String name;
@@ -47,4 +49,10 @@ public class Argument implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		modification.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Array.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Array.java
index 72fcd405..45449362 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Array.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Array.java
@@ -15,6 +15,7 @@ import java.util.Collection;
 import java.util.Iterator;
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
 import fi.semantum.sysdyn.solver.SolverUtils.Slice;
 
 public class Array implements IExpression {
@@ -227,4 +228,15 @@ public class Array implements IExpression {
 		return result;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		for(int i=0;i<elements.size();i++) {
+			Object element = elements.get(i);
+			if(element instanceof IExpression) {
+				((IExpression)element).accept(visitor);
+			}
+		}
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ArraySliceExpression.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ArraySliceExpression.java
index b2813e69..9ed04b14 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ArraySliceExpression.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ArraySliceExpression.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class ArraySliceExpression implements IExpression {
 
 	public IExpression start;
@@ -54,4 +56,11 @@ public class ArraySliceExpression implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		start.accept(visitor);
+		end.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Assignment.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Assignment.java
index fd7f1d06..acaee56a 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Assignment.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Assignment.java
@@ -10,7 +10,7 @@
  *******************************************************************************/
 package fi.semantum.sysdyn.solver;
 
-import org.omg.PortableInterceptor.SUCCESSFUL;
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
 
 public class Assignment {
 	
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Constant.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Constant.java
index d00f2362..9fd58ddd 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Constant.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Constant.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class Constant implements IExpression {
 
 	public Object value;
@@ -49,5 +51,10 @@ public class Constant implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+	}
+	
 }
 
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Declaration.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Declaration.java
index a1490f52..90b2cfc2 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Declaration.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Declaration.java
@@ -11,8 +11,11 @@
  *******************************************************************************/
 package fi.semantum.sysdyn.solver;
 
+import java.nio.channels.UnsupportedAddressTypeException;
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class Declaration implements IExpression {
 
 	public Variable variable;
@@ -48,4 +51,9 @@ public class Declaration implements IExpression {
 		throw new UnsupportedOperationException();
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		throw new UnsupportedOperationException();
+	}
+
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Derivate.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Derivate.java
index 426e3fa7..ef3b6012 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Derivate.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Derivate.java
@@ -12,11 +12,13 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class Derivate implements IExpression {
 
 	private Variable variable;
 	private IExpression[] subscripts;
-	private IExpression e;
+	public IExpression e;
 	
 	public Derivate(Variable variable, IExpression[] subscripts, IExpression e) {
 		this.variable = variable;
@@ -64,4 +66,14 @@ public class Derivate implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		if(subscripts != null) {
+			for(int i=0;i<subscripts.length;i++)
+				subscripts[i].accept(visitor);
+		}
+		e.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Derivative.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Derivative.java
index 51dbf974..037a1745 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Derivative.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Derivative.java
@@ -45,4 +45,9 @@ public class Derivative implements IExpression {
 		throw new UnsupportedOperationException();
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		throw new UnsupportedOperationException();
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Division.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Division.java
index 0f643949..6b7658f2 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Division.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Division.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class Division implements IExpression {
 	
     public IExpression exp1;
@@ -66,4 +68,11 @@ public class Division implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		exp1.accept(visitor);
+		exp2.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ElementwiseProduct.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ElementwiseProduct.java
index d8d3aafb..5888029f 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ElementwiseProduct.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ElementwiseProduct.java
@@ -14,6 +14,8 @@ import java.util.Collection;
 import java.util.Iterator;
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class ElementwiseProduct implements IExpression {
 	
     public IExpression exp1;
@@ -68,4 +70,11 @@ public class ElementwiseProduct implements IExpression {
 		return this;
 	}
 
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		exp1.accept(visitor);
+		exp2.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Equals.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Equals.java
index a92ed1a3..110c99bd 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Equals.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Equals.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class Equals implements IExpression {
 	
     public IExpression exp1;
@@ -55,4 +57,11 @@ public class Equals implements IExpression {
 		return this;
 	}
 
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		exp1.accept(visitor);
+		exp2.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ForArray.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ForArray.java
index 1f66818a..2a268732 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ForArray.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ForArray.java
@@ -14,6 +14,8 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class ForArray implements IExpression {
 
 	private ArrayList<Object> elements = new ArrayList<Object>();
@@ -110,4 +112,15 @@ public class ForArray implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		for(int i=0;i<elements.size();i++) {
+			Object o = elements.get(i);
+			if(o instanceof IExpression) {
+				((IExpression)o).accept(visitor);
+			}
+		}
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/GreaterOrEqualThan.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/GreaterOrEqualThan.java
index 6d462014..4876199c 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/GreaterOrEqualThan.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/GreaterOrEqualThan.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class GreaterOrEqualThan implements IExpression {
 	
     public IExpression exp1;
@@ -49,4 +51,11 @@ public class GreaterOrEqualThan implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		exp1.accept(visitor);
+		exp2.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/GreaterThan.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/GreaterThan.java
index 21d81acc..1a9791d6 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/GreaterThan.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/GreaterThan.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class GreaterThan implements IExpression {
 	
     public IExpression exp1;
@@ -49,4 +51,11 @@ public class GreaterThan implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		exp1.accept(visitor);
+		exp2.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/IExpression.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/IExpression.java
index 6377a3ad..5d58d7f3 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/IExpression.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/IExpression.java
@@ -14,9 +14,14 @@ import java.util.Map;
 
 public interface IExpression {
 
+	public interface ExpressionVisitor {
+		void visit(IExpression expression);
+	}
+	
 	public Object evaluate(IEnvironment environment);
 	public IExpression withBase(IFrame frame, String prefix);
 	public Object getPossibleConstant();
 	public IExpression rewrite(IFrame frame, Map<String, VariableBase> copies);
+	public void accept(ExpressionVisitor visitor);
 	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/IfThenElse.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/IfThenElse.java
index 2176faf4..a95c99e1 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/IfThenElse.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/IfThenElse.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class IfThenElse implements IExpression {
 	
     public IExpression exp;
@@ -56,4 +58,12 @@ public class IfThenElse implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		exp.accept(visitor);
+		t.accept(visitor);
+		e.accept(visitor);
+	}
+
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/LessOrEqualThan.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/LessOrEqualThan.java
index 7c2f2870..b9ab757e 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/LessOrEqualThan.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/LessOrEqualThan.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class LessOrEqualThan implements IExpression {
 	
     public IExpression exp1;
@@ -51,4 +53,11 @@ public class LessOrEqualThan implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		exp1.accept(visitor);
+		exp2.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/LessThan.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/LessThan.java
index 9a808538..db798083 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/LessThan.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/LessThan.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class LessThan implements IExpression {
 	
     public IExpression exp1;
@@ -51,4 +53,11 @@ public class LessThan implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		exp1.accept(visitor);
+		exp2.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Multiplication.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Multiplication.java
index 00397a37..cc4724ab 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Multiplication.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Multiplication.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class Multiplication implements IExpression {
 	
     public IExpression exp1;
@@ -62,4 +64,11 @@ public class Multiplication implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		exp1.accept(visitor);
+		exp2.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Negation.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Negation.java
index cdf125ba..15e9e2df 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Negation.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Negation.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class Negation implements IExpression {
 	
     public IExpression exp;
@@ -46,4 +48,10 @@ public class Negation implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		exp.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/NotEquals.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/NotEquals.java
index 41ca66a5..5c5499ce 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/NotEquals.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/NotEquals.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class NotEquals implements IExpression {
 	
     public IExpression exp1;
@@ -49,4 +51,11 @@ public class NotEquals implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		exp1.accept(visitor);
+		exp2.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/NullModification.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/NullModification.java
index 287d6180..cbafd0d9 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/NullModification.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/NullModification.java
@@ -23,5 +23,10 @@ public class NullModification implements IExpression {
 	public IExpression rewrite(IFrame frame, Map<String, VariableBase> copies) {
 		return this;
 	}
+	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+	}
 
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Or.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Or.java
index e08c3282..375c9240 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Or.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Or.java
@@ -13,6 +13,8 @@ package fi.semantum.sysdyn.solver;
 import java.util.ArrayList;
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class Or implements IExpression {
 	
     public IExpression[] exps;
@@ -59,4 +61,10 @@ public class Or implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		for(IExpression exp : exps) exp.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ParameterDeclaration.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ParameterDeclaration.java
index 1aa811f7..72cbab5e 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ParameterDeclaration.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/ParameterDeclaration.java
@@ -49,4 +49,9 @@ public class ParameterDeclaration implements IExpression {
 		throw new UnsupportedOperationException();
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		throw new UnsupportedOperationException();
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Solver.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Solver.java
index bcd050d4..ca56e4bb 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Solver.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Solver.java
@@ -13,7 +13,15 @@ package fi.semantum.sysdyn.solver;
 
 import java.io.StringReader;
 import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
 
+import org.simantics.utils.datastructures.MapList;
+
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
 import fi.semantum.sysdyn.solver.Model.Globals;
 import fi.semantum.sysdyn.solver.parser.ModelParser;
 import fi.semantum.sysdyn.solver.parser.SimpleNode;
@@ -27,6 +35,7 @@ public class Solver {
 	private Environment env;
 
 	private Object[] newValues;
+	private Object[] derivatives;
 	
 	private double step;
 	private double start;
@@ -51,6 +60,52 @@ public class Solver {
 		ready = false;
 	}
 	
+	private void sortAssignments() {
+
+		final MapList<String,Assignment> asses = new MapList<String,Assignment>();
+		for(Assignment ass : model.assignments) asses.add(ass.target.base.name, ass);
+		
+		final List<VariableBase> found = new ArrayList<VariableBase>();
+		final Set<String> visited = new HashSet<String>();
+
+		ExpressionVisitor sortVisitor = new ExpressionVisitor() {
+			@Override
+			public void visit(IExpression expression) {
+				if(expression instanceof Variable) {
+					Variable var = (Variable)expression;
+					if(visited.add(var.base.name)) {
+						for(Assignment ass : asses.getValues(var.base.name)) {
+							ass.expression.accept(this);
+							if(ass.subscripts != null)
+								for(IExpression e : ass.subscripts) e.accept(this);
+						}
+						found.add(var.base);
+					}
+				}
+			}
+		};
+		
+		// Sort assignments
+		for(Assignment ass : model.assignments) {
+			ass.target.accept(sortVisitor);
+		}
+
+		Collections.sort(model.assignments, new Comparator<Assignment>() {
+
+			@Override
+			public int compare(Assignment o1, Assignment o2) {
+				int i1 = found.indexOf(o1.target.base); 
+				int i2 = found.indexOf(o2.target.base);
+				if(i1 < i2) return -1;
+				else if (i1 > i2) return 1;
+				return 0;
+			}
+
+			
+		});
+		
+	}
+	
 	public void prepare(String input) throws Exception {
 		
 		long startNanos = System.nanoTime();
@@ -79,11 +134,14 @@ public class Solver {
 		
 		env.valueTable = new Object[size+STACK_SIZE];
 		
+		sortAssignments();
+		
 		model.assignmentArray = model.assignments.toArray(new Assignment[model.assignments.size()]);
 		model.derivativeArray = model.derivatives.toArray(new Assignment[model.derivatives.size()]);
 		model.parameterArray = model.parameters.toArray(new ParameterDeclaration[model.parameters.size()]);
 		
 		newValues = new Object[Math.max(model.assignments.size(),model.derivatives.size())];
+		derivatives = new Object[model.derivatives.size()];
 		
 		int condition = 1;
 		int loops = 0;
@@ -185,6 +243,8 @@ public class Solver {
 		return env.getValueArray();
 	}
 	
+	
+	
 	public void step() {
 		// TODO: do something more sensible if the solver is not ready
 		if (!ready) return;
@@ -192,10 +252,19 @@ public class Solver {
 		Assignment[] assignments = model.assignmentArray;
 		Assignment[] derivatives = model.derivativeArray;
 		
+		// first we evaluate, integrate and assign derivatives at previous time step
+		for(int i=0;i<model.derivatives.size();i++) {
+			newValues[i] = derivatives[i].expression.evaluate(env);
+		}
+		for(int i=0;i<model.derivatives.size();i++) {
+			derivatives[i].target.assign(env, assignments[i].subscripts, newValues[i]);
+		}
+
+		// Increment time
 		// should probably be wrapped inside a method or something
 		env.time += env.step;
-		
-		// Solve algebraic equations
+
+		// Next solve algebraic equations
 		for(int i=0;i<assignments.length;i++) {
 			newValues[i] = assignments[i].expression.evaluate(env);
 		}
@@ -203,13 +272,6 @@ public class Solver {
 			assignments[i].target.assign(env, assignments[i].subscripts, newValues[i]);
 		}
 
-		// Solve derivatives
-		for(int i=0;i<model.derivatives.size();i++) {
-			newValues[i] = derivatives[i].expression.evaluate(env);
-		}
-		for(int i=0;i<model.derivatives.size();i++) {
-			derivatives[i].target.assign(env, assignments[i].subscripts, newValues[i]);
-		}
 	}
 	
 	// TODO: implement some on the fly parameter change stuff for different experiment types
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Subtraction.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Subtraction.java
index f7f8763d..79d1404c 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Subtraction.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Subtraction.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class Subtraction implements IExpression {
 	
     public IExpression exp1;
@@ -50,4 +52,11 @@ public class Subtraction implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+		exp1.accept(visitor);
+		exp2.accept(visitor);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/TimeVariable.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/TimeVariable.java
index d2d3e4c6..19e5f299 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/TimeVariable.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/TimeVariable.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 public class TimeVariable implements IExpression {
 
 	@Override
@@ -40,4 +42,9 @@ public class TimeVariable implements IExpression {
 		return this;
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Variable.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Variable.java
index 183d0cc3..8144fba0 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Variable.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/Variable.java
@@ -13,6 +13,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 
 
 public class Variable implements IExpression {
@@ -236,4 +238,9 @@ public class Variable implements IExpression {
 		
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		visitor.visit(this);
+	}
+	
 }
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/VariableBase.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/VariableBase.java
index 1466574b..b00a48cf 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/VariableBase.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/VariableBase.java
@@ -10,8 +10,6 @@
  *******************************************************************************/
 package fi.semantum.sysdyn.solver;
 
-import java.util.Arrays;
-
 import fi.semantum.sysdyn.solver.SolverUtils.Slice;
 
 public class VariableBase {
diff --git a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/VariableDeclaration.java b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/VariableDeclaration.java
index 08c8a49d..51164eac 100644
--- a/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/VariableDeclaration.java
+++ b/fi.semantum.sysdyn.solver/src/fi/semantum/sysdyn/solver/VariableDeclaration.java
@@ -12,6 +12,8 @@ package fi.semantum.sysdyn.solver;
 
 import java.util.Map;
 
+import fi.semantum.sysdyn.solver.IExpression.ExpressionVisitor;
+
 
 public class VariableDeclaration implements IExpression {
 
@@ -53,4 +55,9 @@ public class VariableDeclaration implements IExpression {
 		throw new UnsupportedOperationException();
 	}
 	
+	@Override
+	public void accept(ExpressionVisitor visitor) {
+		throw new UnsupportedOperationException();
+	}
+	
 }
-- 
2.47.1