Interface IRewritable<T>

A object is rewriterable if it knows how to access its immediate children.

Implementations should ensure that you always get the children you just set (rewritable.SetChildren(children).GetChildren() == children), and that successive sets overwrite the earlier operation (rewritable.SetChildren(children1).SetChildren(children2) == rewritable.SetChildren(children2)).

IRewriter<T>.

Namespace: Sawmill

Assembly: Sawmill.dll

Syntax

public interface IRewritable<T>
    where T : IRewritable<T>

Type Parameters

Name	Description
T	The type of the object implementing the interface

Methods

GetChildren()

Get the immediate children of the current instance. GetChildren(T)

Declaration

Children<T> GetChildren()

Returns

Type	Description
Children<T>	The immediate children of the current instance

Examples

Given a representation of the expression (1+2)+3,

Expr expr = new Add(
    new Add(
        new Lit(1),
        new Lit(2)
    ),
    new Lit(3)
);

GetChildren() returns the immediate children of the topmost node.

Expr[] expected = new[]
    {
        new Add(
            new Lit(1),
            new Lit(2)
        ),
        new Lit(3)
    };
Assert.Equal(expected, expr.GetChildren());

RewriteChildren(Func<T, T>)

Update the immediate children of the current instance by applying a transformation function to each one.

Implementations of IRewritable<T> can use DefaultRewriteChildren<T>(T, Func<T, T>), or you can write your own.

NB: A hand-written implementation will not usually be faster than DefaultRewriteChildren<T>(T, Func<T, T>). If your type has a fixed number of children, and that number is greater than two, you may see some performance improvements from implementing this method yourself. Be careful not to rebuild the object if none of the children have changed.

RewriteChildren(Func<T, T>, T)

Declaration

T RewriteChildren(Func<T, T> transformer)

Parameters

Type	Name	Description
System.Func<T, T>	transformer	A transformation function to apply to each of the current instance's immediate children.

Returns

Type	Description
T	A copy of the current instance with updated children.

Examples

Given a representation of the expression (1+2)+3,

Expr expr = new Add(
    new Add(
        new Lit(1),
        new Lit(2)
    ),
    new Lit(3)
);

RewriteChildren(Func<T, T>) only affects the immediate children of the topmost node.

Expr expected = new Add(
    transformer(new Add(
        new Lit(1),
        new Lit(2)
    )),
    transformer(new Lit(3))
);
Assert.Equal(expected, expr.RewriteChildren(transformer));

SetChildren(Children<T>)

Set the immediate children of the currentInstance.

Callers should ensure that newChildren contains the same number of children as was returned by GetChildren().

SetChildren(Children<T>, T)

Declaration

T SetChildren(Children<T> newChildren)

Parameters

Type	Name	Description
Children<T>	newChildren	The new children

Returns

Type	Description
T	A copy of the current instance with updated children.

Examples

Given a representation of the expression (1+2)+3,

Expr expr = new Add(
    new Add(
        new Lit(1),
        new Lit(2)
    ),
    new Lit(3)
);

SetChildren(Children<T>) replaces the immediate children of the topmost node.

Expr expected = new Add(
    new Lit(4),
    new Lit(5)
);
Assert.Equal(expected, expr.SetChildren(Children.Two(new Lit(4), new Lit(5))));