org.cryptimeleon.math.expressions

Interface Expression

All Known Subinterfaces:

BooleanExpression, BoolVariableExpr, ExponentExpr, ExponentVariableExpr, GroupElementExpression, GroupVariableExpr, VariableExpression

All Known Implementing Classes:

AbstractGroupElementExpression, BasicNamedBoolVariableExpr, BasicNamedExponentVariableExpr, BasicNamedGroupVariableExpr, BoolAndExpr, BoolConstantExpr, BoolEmptyExpr, BoolNotExpr, BoolOrExpr, ExponentConstantExpr, ExponentEmptyExpr, ExponentEqualityExpr, ExponentInvExpr, ExponentMulExpr, ExponentNegExpr, ExponentPowExpr, ExponentSumExpr, GroupElementConstantExpr, GroupEmptyExpr, GroupEqualityExpr, GroupInvExpr, GroupOpExpr, GroupPowExpr, PairingExpr

public interface Expression

An expression is a tree of expressions that can be evaluated if it contains no variables. If variables are contained in the expression, they have to be substituted with actual values first.

Method Summary

Modifier and Type	Method and Description
default <T> T	accumulate(java.util.function.BiFunction<T,Expression,T> accumulator, T initialValue) Calls the given accumulator in a pre-order (this, treeWalk[left child], treeWalk[right child]) fashion.
default boolean	containsExprMatchingPredicate(java.util.function.Predicate<Expression> predicate) Checks if an expression fulfilling the given predicate is contained in this expression.
default boolean	containsVariables() Returns true if and only if this expression contains variables.
java.lang.Object	evaluate() Evaluates the expression.
java.lang.Object	evaluate(Substitution substitutions) Evaluates the expression after substituting contained variables.
void	forEachChild(java.util.function.Consumer<Expression> action) Calls action on every (direct) child of this expression.
default java.util.Set<VariableExpression>	getVariables() Returns the set of variables the value of this expression depends on.
default Expression	substitute(java.lang.String variable, Expression substitution)
Expression	substitute(Substitution substitutions) Substitutes variables using the given function.
default Expression	substitute(VariableExpression variable, Expression substitution) Substitutes a specific variable with the given expression.
default void	treeWalk(java.util.function.Consumer<Expression> visitor) Calls the given visitor in a pre-order (this, treeWalk[left child], treeWalk[right child]) fashion.

Method Detail

substitute

default Expression substitute(java.lang.String variable,
                              Expression substitution)

substitute

default Expression substitute(VariableExpression variable,
                              Expression substitution)

Substitutes a specific variable with the given expression.

Parameters:

variable - the variable to replace

substitution - the expression to substitute

Returns:

the expression after substitution

substitute

Expression substitute(Substitution substitutions)

Substitutes variables using the given function.

Parameters:

substitutions - a function mapping variable expressions to their replacement expressions

Returns:

the expression after substitution

evaluate

java.lang.Object evaluate()

Evaluates the expression.

Returns:

the result of evaluation

evaluate

java.lang.Object evaluate(Substitution substitutions)

Evaluates the expression after substituting contained variables.

Parameters:

substitutions - a function mapping variables to expressions that can be evaluated

Returns:

the result of evaluation

getVariables

default java.util.Set<VariableExpression> getVariables()

Returns the set of variables the value of this expression depends on.

containsVariables

default boolean containsVariables()

Returns true if and only if this expression contains variables.

This means that you wouldn't be able to evaluate the expression without substituting the variable with another expression that can be evaluated.

treeWalk

default void treeWalk(java.util.function.Consumer<Expression> visitor)

Calls the given visitor in a pre-order (this, treeWalk[left child], treeWalk[right child]) fashion.

Usual implementation (for binary nodes) is:

     public void treeWalk(Consumer visitor) {
         visitor.accept(this);
         forEachChild(Expression::treeWalk)
     }
 

By contract, implementing objects should at least regard dependent variables as child variable expressions.

forEachChild

void forEachChild(java.util.function.Consumer<Expression> action)

Calls action on every (direct) child of this expression. For example, for a GroupOpExpr, this would call action on the left- and right-hand-side and then return.

accumulate

default <T> T accumulate(java.util.function.BiFunction<T,Expression,T> accumulator,
                         T initialValue)

Calls the given accumulator in a pre-order (this, treeWalk[left child], treeWalk[right child]) fashion.

One can view the implementation as follows:

 v = initialValue
 v = accumulator(v, expr)
 v = accumulator(v, [left subtree]) // recursive call
 v = accumulator(v, [right subtree]) // recursive call
 return v
 

containsExprMatchingPredicate

default boolean containsExprMatchingPredicate(java.util.function.Predicate<Expression> predicate)

Checks if an expression fulfilling the given predicate is contained in this expression.