de.dante.extex.interpreter.primitives.conditional
Class Unless

java.lang.Object
  de.dante.extex.interpreter.type.AbstractCode
      de.dante.extex.interpreter.primitives.conditional.Unless

All Implemented Interfaces:

Code, Localizable, java.io.Serializable

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

Examples:

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

Version:

$Revision: 1.15 $

Author:

Gerd Neugebauer, Sebastian Waschik

See Also:

Serialized Form

serialVersionUID

protected static final long serialVersionUID

The field serialVersionUID contains the version number for the serialization.

See Also:

Constant Field Values

Unless

public Unless(java.lang.String name)

Creates a new object.

Parameters:

name - the name for debugging

execute

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

Overrides:

execute in class AbstractCode

Throws:

InterpreterException

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)

expand

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

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)