org.extex.unit.base.conditional
Class AbstractIf

java.lang.Object
  org.extex.interpreter.type.AbstractCode
      org.extex.unit.base.conditional.AbstractIf

All Implemented Interfaces:

java.io.Serializable, Code, ExpandableCode, PrefixCode

Direct Known Subclasses:

If, Ifcase, Ifcat, Ifcsname, Ifdefined, Ifdim, Ifeof, Iffalse, Iffontchar, Ifhbox, Ifhmode, Ifinner, Ifmmode, Ifnum, Ifodd, Iftrue, Ifvbox, Ifvmode, Ifvoid, Ifx

public abstract class AbstractIf
extends AbstractCode
implements ExpandableCode, PrefixCode

This is the abstract base class for all ifs.

If you want to implement an if-like primitive you should derive it from this class. All you have to do is to implement the method conditional(). Here you define the expression evaluated to determine whether the if or the else branch should be taken.

Version:

$Revision: 4045 $

Author:

Gerd Neugebauer

See Also:

Serialized Form

Field Summary

protected static long

serialVersionUID The constant serialVersionUID contains the id for serialization.

Constructor Summary

AbstractIf(CodeToken token)
Creates a new object.

Method Summary

abstract boolean	conditional(Context context, TokenSource source, Typesetter typesetter) This method computes the boolean value of the conditional.
void	execute(Flags prefix, Context context, TokenSource source, Typesetter typesetter) This method takes the first token and executes it. The result is placed on the stack. This operation might have side effects. To execute a token it might be necessary to consume further tokens.
void	expand(Flags prefix, Context context, TokenSource source, Typesetter typesetter) This method takes the first token and expands it.
protected static Localizer	getMyLocalizer() Getter for the localizer.
boolean	isIf() The ifs are characterized by the return value true of this method.
static boolean	skipToElseOrFi(Context context, TokenSource source, CodeToken primitive) Skip to the next matching \fi or \else Token counting the intermediate \ifs and \fis.

Methods inherited from class org.extex.interpreter.type.AbstractCode

getLocalizer, getName, getToken, isOuter, readResolve, toString, toText, toText

Methods inherited from class java.lang.Object

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

Field Detail

serialVersionUID

protected static final long serialVersionUID

The constant serialVersionUID contains the id for serialization.

See Also:

Constant Field Values

Constructor Detail

AbstractIf

public AbstractIf(CodeToken token)

Creates a new object.

Parameters:

token - the initial token for the primitive

Method Detail

getMyLocalizer

protected static Localizer getMyLocalizer()

Getter for the localizer.

Returns:

the localizer

skipToElseOrFi

public static boolean skipToElseOrFi(Context context,
                                     TokenSource source,
                                     CodeToken primitive)
                              throws HelpingException

Skip to the next matching \fi or \else Token counting the intermediate \ifs and \fis.

This method implements the absorption of tokens at high speed.

Parameters:

context - the interpreter context

source - the source for new tokens

primitive - the name of the invoking primitive

Returns:

true if a matching \else has been found; otherwise return false if a matching \fi has been found

Throws:

HelpingException - in case of en error

conditional

public abstract boolean conditional(Context context,
                                    TokenSource source,
                                    Typesetter typesetter)
                             throws HelpingException,
                                    TypesetterException

This method computes the boolean value of the conditional. If the result is true then the then branch is expanded and the else branch is skipped. Otherwise the then branch is skipped and the else branch is expanded.

Parameters:

context - the interpreter context

source - the source for new tokens

typesetter - the typesetter

Returns:

the boolean value

Throws:

HelpingException - in case of an error

TypesetterException - in case of an error in the typesetter

ConfigurationException - in case of an configuration error

execute

public void execute(Flags prefix,
                    Context context,
                    TokenSource source,
                    Typesetter typesetter)
             throws HelpingException,
                    TypesetterException

This method takes the first token and executes it. The result is placed on the stack. This operation might have side effects. To execute a token it might be necessary to consume further tokens.

Specified by:

execute in interface Code

Overrides:

execute in class AbstractCode

Parameters:

prefix - the prefix controlling the execution

context - the interpreter context

source - the token source

typesetter - the typesetter

Throws:

HelpingException - in case of an error

TypesetterException - in case of an error in the typesetter

See Also:

AbstractCode.execute( org.extex.interpreter.Flags, org.extex.interpreter.context.Context, org.extex.interpreter.TokenSource, org.extex.typesetter.Typesetter)

expand

public void expand(Flags prefix,
                   Context context,
                   TokenSource source,
                   Typesetter typesetter)
            throws HelpingException,
                   TypesetterException

This method takes the first token and expands it. The result is placed on the stack. This means that expandable code does one step of expansion and puts the result on the stack. To expand a token it might be necessary to consume further tokens.

Specified by:

expand in interface ExpandableCode

Parameters:

prefix - the prefix flags controlling the expansion

context - the interpreter context

source - the token source

typesetter - the typesetter

Throws:

HelpingException - in case of an error

TypesetterException - in case of an error in the typesetter

See Also:

ExpandableCode.expand( org.extex.interpreter.Flags, org.extex.interpreter.context.Context, org.extex.interpreter.TokenSource, org.extex.typesetter.Typesetter)

isIf

public boolean isIf()

The ifs are characterized by the return value true of this method. Thus the overwritten method returning the constant is provided in this abstract base class.

Specified by:

isIf in interface Code

Overrides:

isIf in class AbstractCode

Returns:

true iff this is some sort if \if.

See Also:

Code.isIf()