function Constraint::reduce

Reduces the sub-expression starting at $this by skipping degenerate sub-expression and returns first descendant constraint that starts a non-reducible sub-expression.

Returns $this for terminal constraints and for operators that start non-reducible sub-expression, or the nearest descendant of $this that starts a non-reducible sub-expression.

A constraint expression may be modelled as a tree with non-terminal nodes (operators) and terminal nodes. For example:

LogicalOr (operator, non-terminal) + LogicalAnd (operator, non-terminal) | + IsType('int') (terminal) | + GreaterThan(10) (terminal) + LogicalNot (operator, non-terminal) + IsType('array') (terminal)

A degenerate sub-expression is a part of the tree, that effectively does not contribute to the evaluation of the expression it appears in. An example of degenerate sub-expression is a BinaryOperator constructed with single operand or nested BinaryOperators, each with single operand. An expression involving a degenerate sub-expression is equivalent to a reduced expression with the degenerate sub-expression removed, for example

LogicalAnd (operator) + LogicalOr (degenerate operator) | + LogicalAnd (degenerate operator) | + IsType('int') (terminal) + GreaterThan(10) (terminal)

is equivalent to

LogicalAnd (operator) + IsType('int') (terminal) + GreaterThan(10) (terminal)

because the subexpression

+ LogicalOr + LogicalAnd + -

is degenerate. Calling reduce() on the LogicalOr object above, as well as on LogicalAnd, shall return the IsType('int') instance.

Other specific reductions can be implemented, for example cascade of LogicalNot operators

+ LogicalNot + LogicalNot +LogicalNot + IsTrue

can be reduced to

LogicalNot + IsTrue

6 calls to Constraint::reduce()

BinaryOperator::reduce in vendor/phpunit/phpunit/src/Framework/Constraint/Operator/BinaryOperator.php

Reduces the sub-expression starting at $this by skipping degenerate sub-expression and returns first descendant constraint that starts a non-reducible sub-expression.

BinaryOperator::reduce in vendor/phpunit/phpunit/src/Framework/Constraint/Operator/BinaryOperator.php

Reduces the sub-expression starting at $this by skipping degenerate sub-expression and returns first descendant constraint that starts a non-reducible sub-expression.

LogicalNot::reduce in vendor/phpunit/phpunit/src/Framework/Constraint/Operator/LogicalNot.php

Reduces the sub-expression starting at $this by skipping degenerate sub-expression and returns first descendant constraint that starts a non-reducible sub-expression.

LogicalNot::reduce in vendor/phpunit/phpunit/src/Framework/Constraint/Operator/LogicalNot.php

Reduces the sub-expression starting at $this by skipping degenerate sub-expression and returns first descendant constraint that starts a non-reducible sub-expression.

UnaryOperator::failureDescription in vendor/phpunit/phpunit/src/Framework/Constraint/Operator/UnaryOperator.php

Returns the description of the failure.

... See full list

2 methods override Constraint::reduce()

BinaryOperator::reduce in vendor/phpunit/phpunit/src/Framework/Constraint/Operator/BinaryOperator.php

Reduces the sub-expression starting at $this by skipping degenerate sub-expression and returns first descendant constraint that starts a non-reducible sub-expression.

LogicalNot::reduce in vendor/phpunit/phpunit/src/Framework/Constraint/Operator/LogicalNot.php

Reduces the sub-expression starting at $this by skipping degenerate sub-expression and returns first descendant constraint that starts a non-reducible sub-expression.

File

vendor/phpunit/phpunit/src/Framework/Constraint/Constraint.php, line 237

Class

Constraint

@no-named-arguments Parameter names are not covered by the backward compatibility promise for PHPUnit

Namespace

PHPUnit\Framework\Constraint

Code

protected function reduce() : self {
    return $this;
}