org.extex.unit.base.conditional
Class Else

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

All Implemented Interfaces:

java.io.Serializable, Code, ExpandableCode, PrefixCode

public class Else
extends AbstractCode
implements PrefixCode, ExpandableCode

This class provides an implementation for the primitive \else.

The Primitive \else

The primitive \else can appear in the context of a conditional. It terminates the preceding branch and starts the next one.

The primitive \else can not be used alone. It always comes in conjunction with a conditional. A isolated \else leads immediately to an error.

Syntax

The formal description of this primitive is the following:

    ⟨else⟩
      → \else  

Examples

    \ifnum 1<2\else no\fi  

Note:
This primitive is not expandable!

Version:

$Revision: 4439 $

Author:

Gerd Neugebauer

See Also:

Serialized Form

Field Summary

protected static long

serialVersionUID The constant serialVersionUID contains the id for serialization.

Constructor Summary

Else(CodeToken token)
Creates a new object.

Method Summary

void	execute(Flags prefix, Context context, TokenSource source, Typesetter typesetter) Executes the primitive.
void	expand(Flags prefix, Context context, TokenSource source, Typesetter typesetter) This method takes the first token and expands it.

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

getLocalizer, getName, getToken, isIf, 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

Else

public Else(CodeToken token)

Creates a new object.

Parameters:

token - the initial token for the primitive

Method Detail

execute

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

Executes the primitive.

This primitive can only be seen when a conditional has been opened before for which the then branch is expanded. Thus the else branch has to be skipped. Additionally the conditional stack has to be updated. If the conditional stack is already empty then an exception is raised.

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:

Code.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 ConfigurationException,
                   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:

ConfigurationException - in case of an configuration error

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)