GeoTools

Expression parser for human-readeable expressions

Details

  • Type: New Feature New Feature
  • Status: Closed Closed
  • Priority: Minor Minor
  • Resolution: Fixed
  • Affects Version/s: 2.0-b2
  • Fix Version/s: 2.0-b2
  • Component/s: main
  • Labels:
    None

Description

XML is a useful persistence mechanism for Expression objects in geotools, but it fails in terms of useability for Expression creation. A mechanism is needed to create an Expression from human readeable text and to convert an Expression into human readeable text. The latter is a simpler proposition requiring the Expression objects to simply produce the standard text or by providing a visitor which is capable of this task. The proposal for the former involves the creation of a javacc grammar describing a minimal expression language, a jjtree parser, and Expression creating node-walker.

Activity

Ascending order - Click to sort in descending order
Hide
Permalink
Ian Wolfe Schneider added a comment -
Initial jjtree grammar completed.
Incremental Filter/Expression builder completed to reflect grammar.

Demo at:
http://oms.ars.usda.gov/~en/ExpressionDemo.html

Comments appreciated.
Show
Ian Wolfe Schneider added a comment - Initial jjtree grammar completed. Incremental Filter/Expression builder completed to reflect grammar. Demo at: http://oms.ars.usda.gov/~en/ExpressionDemo.html Comments appreciated.
Hide
Permalink
Andrea Aime added a comment -
Ian, did you consider to use jep (jep.sf.net) or jep lite instead of writing your own expression parser?
Show
Andrea Aime added a comment - Ian, did you consider to use jep (jep.sf.net) or jep lite instead of writing your own expression parser?
Hide
Permalink
Ian Wolfe Schneider added a comment -
In response to Andreas comment

"Ian, did you consider to use jep (jep.sf.net) or jep lite instead of writing your own expression parser?"

I did not consider it as our abilities for expressions are more limited then their grammar allows and I wanted more control over the expression building phase and error handling.

Admittedly, their grammar may have been a good place to start from, but after building a F77 grammar (fixed and non-fixed), I felt experienced enough to handle it on my own.
Show
Ian Wolfe Schneider added a comment - In response to Andreas comment "Ian, did you consider to use jep (jep.sf.net) or jep lite instead of writing your own expression parser?" I did not consider it as our abilities for expressions are more limited then their grammar allows and I wanted more control over the expression building phase and error handling. Admittedly, their grammar may have been a good place to start from, but after building a F77 grammar (fixed and non-fixed), I felt experienced enough to handle it on my own.
Hide
Permalink
Ian Wolfe Schneider added a comment -
Geez, I should have closed this a while ago. While the improvements are current in 2.0-b2, their will be deficiencies. It works well for the most part, however.
Show
Ian Wolfe Schneider added a comment - Geez, I should have closed this a while ago. While the improvements are current in 2.0-b2, their will be deficiencies. It works well for the most part, however.

People

  • Assignee:
    Ian Wolfe Schneider
    Reporter:
    Ian Wolfe Schneider
Vote (0)
Watch (1)

Dates

  • Created:
    Updated:
    Resolved: