I want to build a Boolean expression builder in gwt. Something like the following:-
Let's say that the Boolean expression allows only a finite number of unique operands. These operands could take arguments if necessary
E.g.
IsSunny("today") AND IsNotRaining("evening")
IsLeapYear("2012") AND IsFullMoon("today")
There is only a finite set of operands. E.g. IsSunny, IsNotRaining, IsLeapYear, IsFullMoon.
I want to build a GWT UI that allows the client to build such Boolean expressions quickly.
Only the predefined set of operands are supported. Each operand can have different number of arguments and the UI ,use enforce the type and number of arguments. Parenthesis is also allowed.
What would be a good way to build such an UI?
Does GWT have any in built support for it?
Thanks,
Ajay
WARNING: I'm the author of this project but... http://redquerybuilder.appspot.com/ is sort of similar and is written in GWT.
At the moment I've only published the JS friendly version but I'd be happy to make a GWT version available.
Is aimed towards SQL but it is the only thing in this direction that I know of.
I'm up for sharing tips if you want to write it from scratch.
Related
I have a program that can dynamically generate expressions in SMT-LIB format and I am trying to connect these expressions to CVC4 to test satisfiability and get the models. I am wondering if there is a convenient way to parse these strings through the CVC4 C++ API or if it would be best to just store the generated SMT-LIB code in a file and redirect input to the cvc4 executable.
A cursory look at their API doesn't reveal anything obvious, so I don't think they support this mode of operation. In general, loading such statements "on the fly" is tricky, since an expression by itself doesn't make much sense: You'd have to be in a context that has all the relevant sorts defined, along with all the definitions that your expressions rely on, including the selection of the proper logic. That is, for instance, why the corresponding function in z3 has extra arguments: https://z3prover.github.io/api/html/classz3_1_1context.html#af2b9bef14b4f338c7bdd79a1bb155a0f
Having said that, your best bet might be to ask directly at https://github.com/CVC4/CVC4/issues to see if they've something similar.
I used FEST-Assert and moved to AssertJ after it stopped development.
Recently I was pointed to Google repository with another assertions library Truth (http://google.github.io/truth/).
Reading the examples I can not find any advantage of start using it over AssertJ. So it is just matter of taste what to use. But maybe I missed the point, did I?
From one of their comments at GitHub:
The core difference is that the design of Truth includes two specific
areas of extensibility - that of a strategy for proposition failure -
such that a "subject" for Integers, or a subject for Strings can be
re-used in the context of completely different results for failure. A
notable example is the distinction between JUnit's use of
AssertionError and it's AssumptionViolationException. Truth lets you
use the same proposition classes for both.
The other area of flexibility is the ability to create new
assertion/proposition types and hook them in without declaring
possibly conflicting static methods to import. This can be for new
types (say, adding protobufs) or for new uses of existing types (say,
Strings that are treated as Uris). This is the assertAbout() feature.
Other than that, Truth is very similar to AssertJ, since it was
inspired by FEST, of which AssertJ is a fork of the 2.0 development
line.
To sum up, Truth is designed to be a bit more extensible and flexible, but AssertJ will be great (possibly the greatest) for assertions on standard types.
I currently have the following grammar below:
COMPONENT = HEADER BODY
BODY = ELEMENT+
ELEMENT = EXPRESSION | DECLARATION | DESCRIPTION | NAME
I would like to assert that the body must have one of each of the ELEMENT in any order. Currently I am checking this after parsing, I am however curious if it's possible to express this in the grammar using Parser Combinators particularly guards
I tried doing further research regarding this, but nothing seems to come up.
Yes, it is possible. You simply write down all the valid permutations. This gets out of hand, fast.
It isn't worth the trouble to express in the grammar, because in essence you are trying to establish a constraint across the syntax, and grammars are really best at expressing context-free constraints.
Better to parse with grammar rules simply allowing all of the possibles clauses as options, and build your semantic pass (you will have one anyway) to check the additional constraints.
When writing a grammar, you should move as many constraints as possible to the semantic pass instead of the syntactic pass. This greatly improves the ability of the parser to recover from errors during parsing, and allows you to fully control the manner and wording used when reporting the error to users. For the case of permutations, the increased flexibility in the parser will likely reduce the size of the parsing tables as well.
I was a little surprised when I started using Lift how heavily it uses reflection (or appears to), it was a little unexpected in a statically-typed functional language. My experience with JSP was similar.
I'm pretty new to web development, so I don't really know how these tools work, but I'm wondering,
What aspects of web development encourage using reflection?
Are there any tools (in statically typed languages) that handle (1) referring to code from a template page (2) object-relational mapping, in a way that does not use reflection?
Please see lift source. It doesn't use reflection for most of the code that I have studied. Almost everything is statically typed. If you are referring to lift views they are processed as Xml nodes, that too is not reflection.
Specifically referring to the <lift:Foo.bar/> issue:
When <lift:Foo.bar/> is encountered in the code, Lift makes a few guesses, how the original name should have been (different naming conventions) and then calls java.lang.Class.forName to get the class. (Relevant code in LiftSession.scala and ClassHelpers.scala.) It will only find classes registered with addToPackages during boot.
Note that it is also possible (and common) to register classes and methods manually. Convention is still that all transformations must be of the form NodeSeq => NodeSeq because that is the only thing which makes sense for an untyped HTML/XHTML output.
So, what you have is Lift‘s internal registry of node transformations on one side, and on the other side the implicit registry of the module. Both types use a simple string lookup to execute a method. I guess it is arguable if one is more reflection based than the other.
I just want to find all the type casting done in my project.could some one give me starting point for that.
I don't think that Eclipse can do that.
I think that you could possibly use PMD to do this sort of thing; e.g. by defining an rule based on an XPath that selects AST nodes that correspond to typecasts.