/**
* Get the range for a specific variable in an expression. May be null if the range is not
* defined. If only one side of the range is defined, then the min may be -Double.MAX_VALUE, and
* the max may be Double.MAX_VALUE
*
* @param expression the expression to parse
* @param variable the name of the variable
* @throws EmptyRangeException if expression is Constant.FALSE or otherwise unsatisfiable for any
* variable in 'variables'
* @throws ConstantMismatchException is there are constants which contradict each other
* @throws UnsupportedConditionException if there are conditions not suited for interval range
* extraction
*/
public static Interval getVariableRange(Expression expression, String variable)
throws EmptyRangeException, ConstantMismatchException, UnsupportedConditionException {
TreeMap<String, Interval> ranges = new TreeMap<String, Interval>();
Collection<String> equalVars = new ArrayList<String>();
equalVars.add(variable);
equalVars.addAll(getEqualVariables(expression, variable));
Interval rv = null;
try {
Map<String, Double> constantMap = getConstants(expression);
getVariableRangesRecursive(expression, ranges, equalVars, constantMap);
if (ranges.size() > 0) rv = mergeAllRanges(ranges.values());
} catch (AutomatonExportException e) {
// this can occur, for example, if the conditions are not box-edges
throw new EmptyRangeException(
"Error getting range for " + variable + " in expression: " + expression.toDefaultString(),
e);
} catch (EmptyRangeException e) {
throw new EmptyRangeException(
"Empty range for " + variable + " in expression: " + expression.toDefaultString(), e);
} catch (ConstantMismatchException e) {
throw new ConstantMismatchException(
"Constant mismatch in expression: " + expression.toDefaultString(), e);
} catch (UnsupportedConditionException e) {
throw new UnsupportedConditionException(
"Unsupported operation for range extraction in expression: "
+ expression.toDefaultString(),
e);
}
return rv;
}
private void populateCoefficients(Expression e, boolean isLeftHandSide, List<String> vars) {
if (e instanceof Constant) {
Constant c = (Constant) e;
double val = c.getVal();
if (isLeftHandSide) rhs += -val;
else rhs += val;
} else if (e instanceof Variable) {
Variable v = (Variable) e;
int index = getVariableIndex(v, vars);
if (isLeftHandSide) coefficients[index] += 1;
else coefficients[index] -= 1;
} else if (e instanceof Operation) {
Operation o = (Operation) e;
if (o.op == Operator.ADD) {
populateCoefficients(o.getLeft(), isLeftHandSide, vars);
populateCoefficients(o.getRight(), isLeftHandSide, vars);
} else if (o.op == Operator.MULTIPLY) {
Expression l = o.getLeft();
Expression r = o.getRight();
Variable v;
Constant c;
if (l instanceof Variable && r instanceof Constant) {
v = (Variable) l;
c = (Constant) r;
} else if (l instanceof Constant && r instanceof Variable) {
v = (Variable) r;
c = (Constant) l;
} else {
throw new AutomatonExportException(
"Couldn't parse simple linear expression: " + e.toDefaultString());
}
int index = getVariableIndex(v, vars);
if (isLeftHandSide) coefficients[index] += c.getVal();
else coefficients[index] -= c.getVal();
} else
throw new AutomatonExportException(
"Could not parse operation '"
+ o.op.toDefaultString()
+ "' in linear expression: "
+ e.toDefaultString());
} else
throw new AutomatonExportException(
"Could not parse linear expression: " + e.toDefaultString());
}
private static Collection<String> getEqualVariables(Expression expression, String variable) {
Collection<String> rv = new HashSet<String>();
Operation o = expression.asOperation();
if (o != null && o.children.size() == 2) {
Expression leftExp = o.children.get(0);
Expression rightExp = o.children.get(1);
Operator op = o.op;
if (op.equals(Operator.AND)) {
rv.addAll(getEqualVariables(leftExp, variable));
rv.addAll(getEqualVariables(rightExp, variable));
} else if (op.equals(Operator.EQUAL)
&& leftExp instanceof Variable
&& rightExp instanceof Variable) {
Variable left = (Variable) leftExp;
Variable right = (Variable) rightExp;
if (left.name.equals(variable)) rv.add(right.name);
else if (right.name.equals(variable)) rv.add(left.name);
}
}
return rv;
}
/**
* Get ranges for variables in a logical expression, ignores loc assignments
*
* @param expression the expression to parse
* @param ranges where to store the ranges for the variables we encounter
* @throws EmptyRangeException if expression is Constant.FALSE or otherwise unsatisfiable for any
* variable in 'variables'
* @throws ConstantMismatchException if there are conflicting assignments to constants
* @throws UnsupportedConditionException if the expression contains non-interval operations on the
* desired variable
*/
public static void getVariableRanges(Expression expression, TreeMap<String, Interval> ranges)
throws EmptyRangeException, ConstantMismatchException, UnsupportedConditionException {
try {
Map<String, Double> constantMap = getConstants(expression);
getVariableRangesRecursive(expression, ranges, null, constantMap);
} catch (AutomatonExportException e) {
throw new AutomatonExportException(
"Error while parsing expression: " + expression.toDefaultString(), e);
}
}
public static int countVariableOccurances(Expression expression, String variable) {
int rv = 0;
if (expression instanceof Operation) {
Operation o = expression.asOperation();
for (Expression c : o.children) {
rv += countVariableOccurances(c, variable);
}
} else if (expression instanceof Variable) {
Variable v = (Variable) expression;
if (v.name.equals(variable)) ++rv;
}
return rv;
}
public static Map<String, Double> getConstants(Expression expression)
throws ConstantMismatchException {
HashMap<String, Double> rv = new HashMap<String, Double>();
Operation o = expression.asOperation();
if (o != null) {
if (o.op == Operator.AND) {
Map<String, Double> left = getConstants(o.getLeft());
Map<String, Double> right = getConstants(o.getRight());
safePutAll(rv, left);
safePutAll(rv, right);
} else if (o.op == Operator.EQUAL) {
double val = 0;
String varName = null;
Expression leftExp = o.getLeft();
Expression rightExp = o.getRight();
if (leftExp instanceof Variable && rightExp instanceof Constant) {
varName = ((Variable) leftExp).name;
val = ((Constant) rightExp).getVal();
} else if (leftExp instanceof Constant && rightExp instanceof Variable) {
varName = ((Variable) rightExp).name;
val = ((Constant) leftExp).getVal();
}
if (varName != null && !varName.startsWith("loc(")) {
safePut(rv, varName, val);
}
}
}
return rv;
}
/**
* Get the variable ranges and store them into ranges
*
* @param expression the expression to extract from
* @param ranges the place to store them
* @param vars a set of variables we are interested in. if null then get all variables
* @param constantMap a map of variableName -> value for all constants in the original expression
* @throws EmptyRangeException if expression is Constant.FALSE or otherwise unsatisfiable for the
* selected variables
* @throws UnsupportedConditionException if the expression contains non-interval operations on the
* desired variable
*/
private static void getVariableRangesRecursive(
Expression expression,
TreeMap<String, Interval> ranges,
Collection<String> vars,
Map<String, Double> constantMap)
throws EmptyRangeException, UnsupportedConditionException {
Operation o = expression.asOperation();
if (o != null && o.children.size() == 2) {
Expression leftExp = o.children.get(0);
Expression rightExp = o.children.get(1);
Operator op = o.op;
if (op.equals(Operator.AND)) {
TreeMap<String, Interval> left = new TreeMap<String, Interval>();
TreeMap<String, Interval> right = new TreeMap<String, Interval>();
getVariableRangesRecursive(leftExp, ranges, vars, constantMap);
getVariableRangesRecursive(rightExp, ranges, vars, constantMap);
ranges = mergeTreeRanges(left, right);
} else if (expressionContainsVariables(expression, vars)) {
double val = 0;
String varName = null;
// ignore location assignments
if (leftExp instanceof Variable && ((Variable) leftExp).name.startsWith("loc(")) return;
boolean yodaConstraint = false; // if constraint is like '5 < x' instead of the normal order
boolean shouldSkip = false;
if (leftExp instanceof Variable && rightExp instanceof Constant) {
varName = ((Variable) leftExp).name;
val = ((Constant) rightExp).getVal();
yodaConstraint = false;
} else if (leftExp instanceof Constant && rightExp instanceof Variable) {
varName = ((Variable) rightExp).name;
val = ((Constant) leftExp).getVal();
yodaConstraint = true;
} else if (leftExp instanceof Variable && rightExp instanceof Variable) {
// one of them might be an expression constant, which are given by constMap
String leftName = ((Variable) leftExp).name;
Double constVal = constantMap.get(leftName);
if (constVal != null) {
varName = ((Variable) rightExp).name;
val = constVal.doubleValue();
yodaConstraint = true;
} else {
String rightName = ((Variable) rightExp).name;
constVal = constantMap.get(rightName);
if (constVal != null) {
varName = ((Variable) leftExp).name;
val = constVal.doubleValue();
yodaConstraint = false;
} else {
// both are variables. This is only allowed it it's an alias assignment, which
// we detect by checking if the operator is '=='
if (op == Operator.EQUAL) shouldSkip = true;
else
throw new UnsupportedConditionException(
"Unsupported condition for range extraction (one "
+ "side should be variable, the other side a constant): "
+ expression.toDefaultString());
}
}
} else {
throw new UnsupportedConditionException(
"Unsupported condition for range extraction (one "
+ "side should be variable, the other side a constant): "
+ expression.toDefaultString());
}
if (!shouldSkip) {
Interval i = null;
if (op == Operator.EQUAL) {
i = new Interval(val);
ranges.put(varName, i);
} else if ((!yodaConstraint && (op == Operator.GREATER || op == Operator.GREATEREQUAL))
|| (yodaConstraint && (op == Operator.LESS || op == Operator.LESSEQUAL))) {
i = ranges.get(varName);
if (i == null) {
i = new Interval(-Double.MAX_VALUE, Double.MAX_VALUE);
ranges.put(varName, i);
}
i.min = val;
} else if ((!yodaConstraint && (op == Operator.LESS || op == Operator.LESSEQUAL))
|| (yodaConstraint && (op == Operator.GREATER || op == Operator.GREATEREQUAL))) {
i = ranges.get(varName);
if (i == null) {
i = new Interval(-Double.MAX_VALUE, Double.MAX_VALUE);
ranges.put(varName, i);
}
i.max = val;
} else
throw new UnsupportedConditionException(
"Unsupported expression during range extraction: " + expression.toDefaultString());
if (i.max < i.min)
throw new EmptyRangeException("range for " + varName + " is unsatisfiable");
}
}
} else if (expression instanceof Variable) {
Variable v = (Variable) expression;
if (v.name.equals("true")) {
// no restrictions on variable range
} else if (v.name.equals("false")) {
throw new EmptyRangeException("expression contains false");
} else
throw new AutomatonExportException(
"Unsupported expression type (variable as condition?): "
+ expression.toDefaultString());
} else if (expression == Constant.FALSE) // if any variable is false, the range for all is empty
throw new EmptyRangeException("expression contains FALSE");
else if (expression != Constant.TRUE && expressionContainsVariables(expression, vars))
throw new UnsupportedConditionException(
"Unsupported expression during range extraction: " + expression.toDefaultString());
}
