Qt 4.8
|
Implements XPath 2.0's logical expression and
.
More...
#include <qandexpression_p.h>
Implements XPath 2.0's logical expression and
.
The and
expression is the same in XQuery 1.0 as in XPath 2.0.
Definition at line 74 of file qandexpression_p.h.
AndExpression::AndExpression | ( | const Expression::Ptr & | operand1, |
const Expression::Ptr & | operand2 | ||
) |
Definition at line 53 of file qandexpression.cpp.
|
virtual |
Implements QPatternist::Expression.
Reimplemented in QPatternist::OrExpression.
Definition at line 92 of file qandexpression.cpp.
|
virtual |
compress() is the last stage performs in compiling an expression, done after the initial AST build and calling typeCheck(). compress() performs crucial simplifications, either by having drastic performance implications or that some expressions depend on it for proper behavior.
The default implementation performs a sparse conditional constant propagation. In short, a recursive process is performed in the AST which examines if the Expression's operands are constant values, and if so, performs a const fold(AST rewrite) into the result of evaluating the expression in question. This default behavior can be disabled by letting properties() return DisableElimination.
This compress() stage can be relative effective due to the design of XPath, in part because intrinsic functions are heavily used. Many Expressions override compress() and do optimizations specific to what they do. Also, many Expressions performs optimizations in their typeCheck().
context | the static context. Supplies compile time information, and is the channel for communicating error messages. |
Reimplemented from QPatternist::Expression.
Reimplemented in QPatternist::OrExpression.
Definition at line 63 of file qandexpression.cpp.
|
virtual |
Determines the Effective Boolean Value of the expression.
The Effective Boolean Value of a value is not necessarily the same as converting the value to a new value of type xs:boolean.
Note that this function cannot return the empty sequence, evaluateSingleton() must be overridden in order to be able to do that.
The default implementation results in a type error. Hence, this function must be overridden if such behavior is not of interest.
Reimplemented from QPatternist::Expression.
Reimplemented in QPatternist::OrExpression.
Definition at line 58 of file qandexpression.cpp.
|
virtual |
Returns a list of Sequence Types, describing the type of each of the expression's operands. Hence, this function has a relationship to the operands() function:
- The lengths of the lists returned by expectedOperandTypes() and operands() should always be equal in length, since one cannot describe the type of a non-existent operand(and all operands must have type information). - A significant difference between the two functions is that while the type of objects in the list returned by operands() may vary between compilations/static context, simply because the particular Expression is part of different XPath expressions, the types in the list returned by expectedOperandTypes is always the same since the function/operator signature never changes.
This function should not be confused with staticType(), which returns the static type of the expression itself, not its operands. The function call is an expression where this is clear: the type of the return value is not the same as the arguments' types. The static type of the operands supplied to the expression can be determined via the staticType() function of the instances returned by operands().
If the expression has no operands, an empty list should be returned.
Implements QPatternist::Expression.
Definition at line 79 of file qandexpression.cpp.
|
virtual |
Implements QPatternist::Expression.
Definition at line 87 of file qandexpression.cpp.