uk.ac.starlink.ttools.filter
Class SortHeadFilter

java.lang.Object
  extended by uk.ac.starlink.ttools.filter.BasicFilter
      extended by uk.ac.starlink.ttools.filter.SortHeadFilter
All Implemented Interfaces:
ProcessingFilter

public class SortHeadFilter
extends BasicFilter

Filter for returning the first (or last) few rows of a sorted table. This is functionally equivalent to using sort followed by head, but the algorithm is different (a complete sort is not necessary), so this way will usually be faster.

Since:
12 Oct 2005
Author:
Mark Taylor

Constructor Summary
SortHeadFilter()
           
 
Method Summary
 ProcessingStep createStep(Iterator argIt)
          Creates a new ProcessingStep based on a sequence of command-line arguments.
protected  String[] getDescriptionLines()
           
 
Methods inherited from class uk.ac.starlink.ttools.filter.BasicFilter
explainSyntax, getDescription, getName, getUsage
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

SortHeadFilter

public SortHeadFilter()
Method Detail

getDescriptionLines

protected String[] getDescriptionLines()
Specified by:
getDescriptionLines in class BasicFilter

createStep

public ProcessingStep createStep(Iterator argIt)
                          throws ArgException
Description copied from interface: ProcessingFilter
Creates a new ProcessingStep based on a sequence of command-line arguments. The argIt argument is an iterator over the command-line arguments positioned just before any arguments intended for this filter. If legal, any that can be comprehended by this filter should be read (iterated over) and removed, and a ProcessingStep should accordingly be returned. In the case of a successful return, it is essential that no arguments other than the ones intended for this filter are read from the iterator.

If the argument list is badly-formed as far as this filter is concerned, an ArgException should be thrown. If its usageFrament is blank, it will be filled in later using this mode's usage text.

Parameters:
argIt - iterator over command-line arguments positioned at the first one
Throws:
ArgException


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