Class ConstantHoister

Hoists constants out of an expression tree into an environment.

Inheritance
System.Object
ConstantHoister
Implements
Namespace: System.Linq.CompilerServices
Assembly: Nuqleon.Linq.CompilerServices.dll
Syntax
public class ConstantHoister : Object, IConstantHoister

Constructors

ConstantHoister()

Creates a new constant hoister without an exclusion list.

Declaration
public ConstantHoister()

ConstantHoister(Boolean, LambdaExpression[])

Creates a new constant hoister with the specified exclusion list.

Declaration
public ConstantHoister(bool useDefaultForNull, params LambdaExpression[] exclusions)
Parameters
Type Name Description
System.Boolean useDefaultForNull

Indicates whether to substitute null references for default expressions rather than hoisting them.
System.Linq.Expressions.LambdaExpression[] exclusions

Exclusion list for constant sites that should be excluded from hoisting.

Methods

Create(Boolean, LambdaExpression[])

Creates a new constant hoister using the specified exclusion list for constant sites to exclude from hoisting.

Declaration
public static ConstantHoister Create(bool useDefaultForNull, params LambdaExpression[] exclusions)
Parameters
Type Name Description
System.Boolean useDefaultForNull

Indicates whether to substitute null references for default expressions rather than hoisting them.
System.Linq.Expressions.LambdaExpression[] exclusions

Exclusion list for constant sites that should be excluded from hoisting. These sites are specified as lambda parameters.
Returns
Type Description
ConstantHoister

Constant hoister instance using the specified exclusion list.
Examples

Consider the following usage of a constant hoister:

  var h = ConstantHoister.Create(
              (Expression<Func<string, string>>)(s => string.Format(s, default(object[])))
          );

  var e = (Expression<Func<string>>)(() => string.Format("{0} {1}", "bar", 123));
  var r = h.Hoist(e.Body);

results in the following environment and tree:

  r.Expression  = string.Format("{0} {1}", p0, p1)
  r.Environment = { p0 -> "bar", p1 -> 123 }

where the first argument to the string.Format call did not get hoisted.

Hoist(ConstantExpression)

Provides a hook for derived classes to rewrite the hoisted constants, e.g. to intern the constant's value.

Declaration
protected virtual Expression Hoist(ConstantExpression expression)
Parameters
Type Name Description
System.Linq.Expressions.ConstantExpression expression

The constant expression that has been hoisted.
Returns
Type Description
System.Linq.Expressions.Expression

An expression equivalent to the original hoisted expression.

Hoist(Expression)

Hoists constants in the specified expression and returns an environment.

Declaration
public ExpressionWithEnvironment Hoist(Expression expression)
Parameters
Type Name Description
System.Linq.Expressions.Expression expression

Expression to hoist constants in.
Returns
Type Description
ExpressionWithEnvironment

Expression bound by an environment consisting of the hoisted constants.

Hoist(Expression, Boolean)

Hoists constants in the specified expression and returns an environment.

Declaration
public static ExpressionWithEnvironment Hoist(Expression expression, bool useDefaultForNull)
Parameters
Type Name Description
System.Linq.Expressions.Expression expression

Expression to hoist constants in.
System.Boolean useDefaultForNull

Indicates whether to substitute null references for default expressions rather than hoisting them.
Returns
Type Description
ExpressionWithEnvironment

Expression bound by an environment consisting of the hoisted constants.

Explicit Interface Implementations

IConstantHoister.Hoist(Expression)

Hoists constants in the specified expression and returns an environment.

Declaration
IExpressionWithEnvironment IConstantHoister.Hoist(Expression expression)
Parameters
Type Name Description
System.Linq.Expressions.Expression expression

Expression to hoist constants in.
Returns
Type Description
IExpressionWithEnvironment

Expression bound by an environment consisting of the hoisted constants.

Implements