water.rapids.ast

Class AstRoot<T extends AstRoot<T>>

java.lang.Object

water.Iced<T>

water.rapids.ast.AstRoot<T>

All Implemented Interfaces:

java.io.Externalizable, java.io.Serializable, java.lang.Cloneable, Freezable<T>

Direct Known Subclasses:

AstExec, AstFrame, AstParameter, AstPrimitive, AstRow

public abstract class AstRoot<T extends AstRoot<T>>
extends Iced<T>

Base class for all nodes in Rapids language Abstract Syntax Tree.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
AstRoot()

Method Summary

Modifier and Type	Method and Description
abstract java.lang.String	description() Return the detailed description (help) for what this language construct does or how it is supposed to be used.
abstract java.lang.String	example() Return an example of how this Ast construct ought to be used.
abstract Val	exec(Env env) "Execute" this AST expression, and return the result.
abstract java.lang.String	str() String representation of this Ast object in the Rapids language.
java.lang.String	toString()

Methods inherited from class water.Iced

asBytes, clone, copyOver, frozenType, read, readExternal, readJSON, reloadFromBytes, toJsonBytes, toJsonString, write, writeExternal, writeJSON

Methods inherited from class java.lang.Object

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

Constructor Detail

AstRoot

public AstRoot()

Method Detail

exec

public abstract Val exec(Env env)

"Execute" this AST expression, and return the result. For different ASTs this may have different interpretation. For example, consider this Rapids expression:

    (mean frame True False)

It will be parsed into the following structure:

 AstExec() instance with
    _asts = [AstMean() singleton instance,
             new AstId(frame),
             AstConst.TRUE,
             AstConst.FALSE]
 

Execution of AstExec will execute its first argument, _asts[0], verify that it produces a function (ValFun), then call AstPrimitive.apply(Env, Env.StackHelp, AstRoot[]) on that function passing down the list of _asts arguments.

The AstMean class will in turn execute all its arguments, where execution of AstId fetches the referred symbol from the environment, and execution of AstConst returns the value of that constant.

Certain other functions may choose not to evaluate all their arguments (for example boolean expressions providing short-circuit evaluation).

str

public abstract java.lang.String str()

String representation of this Ast object in the Rapids language. For AstPrimitives this is the name of the function; for AstParameters this is either the name of the variable, or the value of the numeric constant that the parameter represents. For more complicated constructs such as AstExec or AstFunction this method should return those objects as a Rapids string.

example

public abstract java.lang.String example()

Return an example of how this Ast construct ought to be used. This method is used to build documentation for the Rapids language. It is different from str(), in particular it must provide a valid example even in a static context. For example, an AstStr may return "Hello, world!" as an example. At the same time, for different AstPrimitives this method should generally provide a typical example of how that function is to be used.

Return null to indicate that the object should not be included in the documentation.

description

public abstract java.lang.String description()

Return the detailed description (help) for what this language construct does or how it is supposed to be used. This method is used in conjunction with example() to build the documentation of the Rapids language.

If you need to include any formatting, then please use Markup language. Although it is up to the client to support it, Markup is one of the simplest and easiest alternatives.

Return null to indicate that the object should not be included in the documentation.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object