com.svincent.smalljava
Class Expr

java.lang.Object
  |
  +--com.svincent.util.BaseObject
        |
        +--com.svincent.smalljava.Expr

Direct Known Subclasses:

Expr.Begin, com.svincent.smalljava.Expr.BinaryExpr, Expr.BooleanConst, Expr.Call, Expr.Comment, Expr.DoubleConst, Expr.GetField, Expr.GetLocal, Expr.GetStatic, Expr.If, Expr.IntConst, Expr.New, Expr.NewArray, Expr.NullConst, Expr.Return, Expr.SetArray, Expr.SetField, Expr.SetLocal, Expr.StringConst, Expr.SuperConstructor, Expr.This, Expr.While

public abstract class Expr

extends BaseObject

Expr represents an executable expression. Most of the expression types you've come to know and love are here: ifs, whiles, arithmetic, field manipulation, etc. They're all right here, in Texas.

Author:

Shawn Vincent

Inner Class Summary

static class	Expr.Begin Execute a series of expressions, one after another.
static class	Expr.BooleanConst Return the given boolean constant.
static class	Expr.Call Call a method.
static class	Expr.Comment A comment.
static class	Expr.DoubleConst Return the given double constant.
static class	Expr.EQ The normal == binary operator.
static class	Expr.GE The normal >= binary operator.
static class	Expr.GetField Get the value from an instance field
static class	Expr.GetLocal Get the value from a local variable
static class	Expr.GetStatic Get the value from a static field
static class	Expr.GT The normal > binary operator.
static class	Expr.If If condition evaluates to true, evaluate the then clase.
static class	Expr.IntConst Return the given integer constant.
static class	Expr.LE The normal <= binary operator.
static class	Expr.LT The normal < binary operator.
static class	Expr.Minus The normal - binary operator.
static class	Expr.NE The normal != binary operator.
static class	Expr.New Construct a new instance of the named class.
static class	Expr.NewArray Construct a new array instance for containing the given type (Only makes single-dimensional arrays, for now) Also ignores types of initializer things.
static class	Expr.NullConst Return the null constant..
static class	Expr.Plus The normal + binary operator.
static class	Expr.Return Return a value from a method.
static class	Expr.SetArray Assign a value to an array slot
static class	Expr.SetField Assign a value to an instance field
static class	Expr.SetLocal Assign a value to a local variable
static class	Expr.StringConst Return the given String constant.
static class	Expr.SuperConstructor call the null-arg super constructor..
static class	Expr.This Access the magic variable 'this'.
static class	Expr.While Loop around, executing instructions until the given condition evaluates to 'true'.

Field Summary

static boolean	debugTypecheck Set to true to debug typecheck algorithms
static Expr[]	EmptyArray A convenient empty Expression array.

Constructor Summary

Expr()

Method Summary

protected abstract SmallType	deriveType(SmallMethod m) Actually do the work.
protected SmallType	evalType(SmallMethod m) Not to be called by users.
protected abstract void	generateInstructions(ClassFileWriter out, VariableTable vars) Generate a list of JVM instructions for this expression node.
SmallType	getResultType() Get the type of the result of this expression.
protected boolean	printTrailingSemi() Returns true if, after printing this expression as a statement, there should be a trailing semicolon printed.
java.lang.String	tag()
abstract void	writeAsJava(IndentPrintWriter out) Write this expression out as Java source code.

Methods inherited from class com.svincent.util.BaseObject

dump, dump, dumpToString

Methods inherited from class java.lang.Object

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

Field Detail

debugTypecheck

public static final boolean debugTypecheck

Set to true to debug typecheck algorithms

EmptyArray

public static final Expr[] EmptyArray

A convenient empty Expression array.

Constructor Detail

Expr

public Expr()

Method Detail

evalType

protected SmallType evalType(SmallMethod m)
                      throws SmallJavaValidationException

Not to be called by users. Evaluates the type of this expression, and caches the value, so that 'getResultType' can work.

See Also:

getResultType()

deriveType

protected abstract SmallType deriveType(SmallMethod m)
                                 throws SmallJavaValidationException

Actually do the work. deriveType should call 'evalType' for recursion, and super.deriveType to repeat parent work. These simple rules for you and me will result in a happy world where the type returned is always cached appropriately.

See Also:

evalType(SmallMethod), getResultType()

getResultType

public SmallType getResultType()

Get the type of the result of this expression. Can only be called after the declaring class has been finalized.

tag

public java.lang.String tag()

Overrides:

tag in class BaseObject

writeAsJava

public abstract void writeAsJava(IndentPrintWriter out)

Write this expression out as Java source code.

generateInstructions

protected abstract void generateInstructions(ClassFileWriter out,
                                             VariableTable vars)

Generate a list of JVM instructions for this expression node.

printTrailingSemi

protected boolean printTrailingSemi()

Returns true if, after printing this expression as a statement, there should be a trailing semicolon printed. Notable exceptions are {...} constructs, and ifs and whiles.