org.extex.unit.etex.register.dimen
Class Dimenexpr

java.lang.Object
  org.extex.interpreter.type.AbstractCode
      org.extex.unit.etex.register.dimen.Dimenexpr

All Implemented Interfaces:

java.io.Serializable, CountConvertible, DimenConvertible, Code, Theable

public class Dimenexpr
extends AbstractCode
implements DimenConvertible, CountConvertible, Theable

This class provides an implementation for the primitive \dimenexpr.

The Primitive \dimenexpr

The primitive \dimenexpr provides a means to use a inline way of writing mathematical expressions to be evaluated. Mathematical expressions can be evaluated in ExTeX using \advance, \multiply, and \divide. Nevertheless those primitives result in an assignment. This is not the case for \dimenexpr. Here the intermediate results are not stored in dimen registers but kept internally. Also the application of \afterassignment and \tracingassigns is suppressed.

The mathematical expression to be evaluated can be made up of the basic operations addition (+), subtraction (-), multiplication (*) with numbers, and division(/) by numbers. The unary minus can be used. Parentheses can be used for grouping. Anything which looks like a length can be used as argument. White-space can be used freely without any harm.

The expression is terminated at the first token which can not be part of an expression. For instance a letter may signal the end of the expression. If the expression should terminate without a proper token following it, the token \relax can be used to signal the end of the expression. This \relax token is silently consumed by \dimenexpr.

The primitive \dimenexpr can be used in any place where a dimen is required. This includes assignments to dimen registers and comparisons.

Syntax

The formal description of this primitive is the following:

    ⟨dimenexpr⟩
      → \dimenexpr ⟨expr⟩ \relax
      |   \dimenexpr ⟨expr⟩

    ⟨expr⟩
      → ⟨operand⟩
      |   ⟨operand⟩ + ⟨expr⟩
      |   ⟨operand⟩ - ⟨expr⟩

    ⟨operand⟩
      → ⟨dimen⟩
      |   ⟨operand⟩ * ⟨number⟩
      |   ⟨number⟩ * ⟨operand⟩
      |   ⟨operand⟩ / ⟨number⟩
      |   - ⟨expr⟩
      |   ( ⟨expr⟩ )   

Examples

   \count1=\dimenexpr 23pt \relax 

   \count1=\dimenexpr 2 * 3pt \relax 

   \count1=\dimenexpr 2pt*\count2  

   \count1=\dimenexpr 2*(1pt+3em)  

   \count1=\dimenexpr 2*-\dimen0  

Version:

$Revision: 4770 $

Author:

Gerd Neugebauer

See Also:

Serialized Form

Field Summary

protected static long

serialVersionUID The constant serialVersionUID contains the id for serialization.

Constructor Summary

Dimenexpr(CodeToken token)
Creates a new object.

Method Summary

long	convertCount(Context context, TokenSource source, Typesetter typesetter) This method converts a register into a count.
long	convertDimen(Context context, TokenSource source, Typesetter typesetter) This method converts a register into a dimen.
Tokens	the(Context context, TokenSource source, Typesetter typesetter) This method is the getter for the description of the primitive.

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

execute, 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

Dimenexpr

public Dimenexpr(CodeToken token)

Creates a new object.

Parameters:

token - the initial token for the primitive

Method Detail

convertCount

public long convertCount(Context context,
                         TokenSource source,
                         Typesetter typesetter)
                  throws HelpingException,
                         TypesetterException

This method converts a register into a count. It might be necessary to read further tokens to determine which value to use. For instance an additional register number might be required. In this case the additional arguments Context and TokenSource can be used.

Specified by:

convertCount in interface CountConvertible

Parameters:

context - the interpreter context

source - the source for new tokens

typesetter - the typesetter to use for conversion

Returns:

the converted value

Throws:

HelpingException - in case of an error

TypesetterException - in case of an error in the typesetter

See Also:

CountConvertible.convertCount( org.extex.interpreter.context.Context, org.extex.interpreter.TokenSource, org.extex.typesetter.Typesetter)

convertDimen

public long convertDimen(Context context,
                         TokenSource source,
                         Typesetter typesetter)
                  throws HelpingException,
                         TypesetterException

This method converts a register into a dimen. It might be necessary to read further tokens to determine which value to use. For instance an additional register number might be required. In this case the additional arguments Context and TokenSource can be used. The return value is the length in scaled points.

Specified by:

convertDimen in interface DimenConvertible

Parameters:

context - the interpreter context

source - the source for new tokens

typesetter - the typesetter to use for conversion

Returns:

the converted value in sp

Throws:

HelpingException - in case of an error

TypesetterException - in case of an error in the typesetter

See Also:

DimenConvertible.convertDimen( org.extex.interpreter.context.Context, org.extex.interpreter.TokenSource, org.extex.typesetter.Typesetter)

the

public Tokens the(Context context,
                  TokenSource source,
                  Typesetter typesetter)
           throws HelpingException,
                  TypesetterException,
                  CatcodeException

This method is the getter for the description of the primitive.

Specified by:

the in interface Theable

Parameters:

context - the interpreter context

source - the source for further tokens to qualify the request

typesetter - the typesetter to use

Returns:

the description of the primitive as list of Tokens

Throws:

HelpingException - in case of an error

TypesetterException - in case of an error

CatcodeException - in case of an error in token creation

See Also:

Theable.the( org.extex.interpreter.context.Context, org.extex.interpreter.TokenSource, org.extex.typesetter.Typesetter)