Class Unless

  extended byde.dante.extex.interpreter.type.AbstractCode
      extended byde.dante.extex.interpreter.primitives.conditional.Unless
All Implemented Interfaces:
Code, Localizable,

public class Unless
extends AbstractCode

This class provides an implementation for the primitive \if.

The Primitive \unless

Copied of the eTeX reference.

TeX has, by design, a rather sparse set of conditional primitives: \ifeof, \ifodd, \ifvoid, etc., have no complementary counterparts. Whilst this normally poses no problems since each accepts both a \then (implicit) and an \else (explicit) part, they fall down when used as the final \if... of a \loop ... \if ... \repeat construct, since no \else is allowed after the final \if.... \unless allows the sense of all Boolean conditionals to be inverted, and thus (for example) \unless \ifeof yields true iff end-of-file has not yet been reached.

The formal description of this primitive is the following: TODO missing documentation


    \unless\if\x\y not ok \fi  

$Revision: 1.15 $
Gerd Neugebauer, Sebastian Waschik
See Also:
Serialized Form

Field Summary
protected static long serialVersionUID
          The field serialVersionUID contains the version number for the serialization.
Constructor Summary
Unless(java.lang.String name)
          Creates a new object.
Method Summary
 void execute(Flags prefix, Context context, TokenSource source, Typesetter typesetter)
          This method takes the first token and executes it.
 void expand(Flags prefix, Context context, TokenSource source, Typesetter typesetter)
Methods inherited from class de.dante.extex.interpreter.type.AbstractCode
enableLocalization, getLocalizer, getName, isIf, isOuter, printable, printableControlSequence, readResolve, setName, toString
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail


protected static final long serialVersionUID
The field serialVersionUID contains the version number for the serialization.

See Also:
Constant Field Values
Constructor Detail


public Unless(java.lang.String name)
Creates a new object.

name - the name for debugging
Method Detail


public void execute(Flags prefix,
                    Context context,
                    TokenSource source,
                    Typesetter typesetter)
             throws InterpreterException
Description copied from interface: Code
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
execute in class AbstractCode
See Also:
Code.execute( de.dante.extex.interpreter.Flags, de.dante.extex.interpreter.context.Context, de.dante.extex.interpreter.TokenSource, de.dante.extex.typesetter.Typesetter)


public void expand(Flags prefix,
                   Context context,
                   TokenSource source,
                   Typesetter typesetter)
            throws InterpreterException
See Also:
ExpandableCode.expand( de.dante.extex.interpreter.Flags, de.dante.extex.interpreter.context.Context, de.dante.extex.interpreter.TokenSource, de.dante.extex.typesetter.Typesetter)