org.cryptimeleon.math.expressions.group

Class GroupEmptyExpr

java.lang.Object

org.cryptimeleon.math.expressions.group.AbstractGroupElementExpression

org.cryptimeleon.math.expressions.group.GroupEmptyExpr

All Implemented Interfaces:

Expression, GroupElementExpression

public class GroupEmptyExpr
extends AbstractGroupElementExpression

Represents the neutral group element of the given group. Has utility over using a GroupElementConstantExpr with a neutral element in the sense that the neutral element is replaced on a group operation, leading to saving one potential group operation.

Field Summary

Fields inherited from class org.cryptimeleon.math.expressions.group.AbstractGroupElementExpression

group

Constructor Summary

Constructors

Constructor and Description
GroupEmptyExpr()
GroupEmptyExpr(Group group)

Method Summary

Modifier and Type	Method and Description
GroupElement	evaluate(Substitution substitutions) Evaluates the expression after substituting contained variables.
GroupOpExpr	flatten(ExponentExpr exponent) Linearizes the expression \(\text{this}^\text{exponent}\).
void	forEachChild(java.util.function.Consumer<Expression> action) Calls action on every (direct) child of this expression.
GroupElementExpression	inv()
GroupOpExpr	linearize() Returns an equivalent expression of the form y * f(groupVariables, exponentVariables), where y is constant (no variables), and the expression f is linear.
GroupElementExpression	op(GroupElement rhs)
GroupElementExpression	op(GroupElementExpression rhs)
GroupElementExpression	pow(java.math.BigInteger exponent)
GroupElementExpression	pow(ExponentExpr exponent)
GroupElementExpression	pow(RingElement exponent)
GroupElementExpression	substitute(Substitution substitutions) Substitutes variables using the given function.

Methods inherited from class org.cryptimeleon.math.expressions.group.AbstractGroupElementExpression

getGroup, getGroupOrderIfKnown

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.cryptimeleon.math.expressions.group.GroupElementExpression

evaluate, flatten, isEqualTo, isEqualTo, isEqualTo, op, opPow, opPow, opPow, opPow, opPow, opPow, opPow, opPow, pow, pow, precompute, substitute, substitute

Methods inherited from interface org.cryptimeleon.math.expressions.Expression

accumulate, containsExprMatchingPredicate, containsVariables, getVariables, treeWalk

Constructor Detail

GroupEmptyExpr

public GroupEmptyExpr(Group group)

GroupEmptyExpr

public GroupEmptyExpr()

Method Detail

evaluate

public GroupElement evaluate(Substitution substitutions)

Description copied from interface: Expression

Evaluates the expression after substituting contained variables.

Parameters:

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

Returns:

the result of evaluation

forEachChild

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

Description copied from interface: Expression

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.

substitute

public GroupElementExpression substitute(Substitution substitutions)

Description copied from interface: Expression

Substitutes variables using the given function.

Parameters:

substitutions - a function mapping variable expressions to their replacement expressions

Returns:

the expression after substitution

op

public GroupElementExpression op(GroupElementExpression rhs)

op

public GroupElementExpression op(GroupElement rhs)

pow

public GroupElementExpression pow(ExponentExpr exponent)

pow

public GroupElementExpression pow(java.math.BigInteger exponent)

pow

public GroupElementExpression pow(RingElement exponent)

inv

public GroupElementExpression inv()

linearize

public GroupOpExpr linearize()
                      throws java.lang.IllegalArgumentException

Description copied from interface: GroupElementExpression

Returns an equivalent expression of the form y * f(groupVariables, exponentVariables), where y is constant (no variables), and the expression f is linear. Linearity means that

 f(groupVariables, exponentVariables) * f(groupVariables2, exponentVariables2)
 = f(groupVariables * groupVariables2, exponentVariables + exponentVariables2)
 

The exact result is a GroupOpExpr where the left-hand-side y fulfills y.containsVariables() == false and the right-hand side is linear.

Throws:

java.lang.IllegalArgumentException - if it's not possible to form the desired output (e.g., the input is something like \(g^{x_1 \cdot x_2}\) for variables \(x_1, x_2\)).

flatten

public GroupOpExpr flatten(ExponentExpr exponent)

Description copied from interface: GroupElementExpression

Linearizes the expression \(\text{this}^\text{exponent}\).