Is there any support for debugging xpath user-defined functions in the latest Saxon PE? I've used the trace function, but it seems to work in some contexts and not in others. I'm sure there's a logic to that, but I don't understand it. I'm really looking for something simple like something akin to <xsl:message>.
Thanks in advance.
I suspect your calls on trace() are working, but the output is confusing because of lazy evaluation, which means that things are often evaluated in a different order from what you expect. In fact, the optimizer can sometimes rearrange the expressions you write in your source into something quite different.
Have you tried the debuggers in tools like Stylus Studio or oXygen? Typically these disable some optimizations, making the sequence of execution more comprehensible.
Related
Here are 4 deeply related questions about F# code quotations -
How do I invoke an F# code quotation?
Will it be invoked in a manner less efficient than if it were just a plain old F# lambda? to what degree?
Will it require run-time support for advanced reflection or code-emitting functionality (which is often absent or prohibited from embedded platforms I am targeting)?
Quotations are just data, so you can potentially "invoke" them in whatever clever way you come up with. For instance, you can simply walk the tree and interpret each node as you go, though that wouldn't perform particularly well if you're trying use the value many times and its not a simple value (e.g. if you've quoted a lambda that you want to invoke repeatedly).
If you want something more performant (and also simpler), then you can just use Linq.RuntimeHelpers.LeafExpressionConverter.EvaluateQuotation. This doesn't support all possible quotations (just roughly the set equivalent to C# LINQ expressions), and it's got to do a bit more work to actually generate IL, etc., but this should be more efficient if you're reusing the result. This does its work by first converting the quotation to a C# expression tree and then using the standard Compile function defined there, so it will only work on platforms that support that.
So iOS 6 deprecates presentModalViewController:animated: and dismissModalViewControllerAnimated:, and it replaces them with presentViewController:animated:completion: and dismissViewControllerAnimated:completion:, respectively. I suppose I could use find-replace to update my app, although it would be awkward with the present* methods, since the controller to be presented is different every time. I know I could handle that situation with a regex, but I don't feel comfortable enough with regex to try using it with my 1000+-files-big app.
So I'm wondering: Does Xcode have some magic "update deprecated methods" command or something? I mean, I've described my particular situation above, but in general, deprecations come around with every OS release. Is there a better way to update an app than simply to use find-replace?
You might be interested in Program Transformation Systems.
These are tools that can automatically modify source code, using pattern-directed source-to-source transformations ("if you see this source-level pattern, replace it by that source-level pattern") that operate on code structures rather than text. Done properly, these transformations can be reliable and semantically correct, and they're a lot easier to write than low-level procedural code that navigates and smashes nanoscopic actual tree structures.
It is not the case that using such tools is easy; such tools have to know how to parse the language of interest into compiler data structures, (e.g., ObjectiveC), process the patterns, and regenerate compilable source code from the modified structures. Even with the basic transformation engine, somebody needs to carefully define parsers (and unparsers!) for the dialects of the languages of interest. And it takes time to learn how to use such a even if you have such parsers/unparsers. This is worth it if the changes you need to make are "regular" (in the program transformation sense, not the regexp sense) and widespread (as yours seem to be).
Our DMS Software Reengineering toolkit has an ObjectiveC front end, and can carry out such transformations.
no there is no magic like that
I understand that over a thousand built-in rewrite rules in Mathematica populate the global rules table by default. Is there any way to get Mathematica to give a full or even partial list of those rules?
The best way is to get a job at Wolfram Research.
Failing that, I think that for things not completely compiled into the kernel you can recover most of the rules/definitions. Look at
Attributes[fn]
where fn is the command that you're interested in. If it returns
{Protected, ReadProtected}
then there's something you can get a look at (although often it's just a MakeBoxes (formatting) definition or a AutoLoad/Stub type definition). To see what's there run
Unprotect[fn];
ClearAttributes[fn, ReadProtected];
??fn
Quite often you'll have to run an example of the command to load it if it was a stub. You'll also have to dig down from the user-facing commands to the back-end implementations.
Eventually you'll most likely reach a core command that is compiled into the kernel that you can not see the details of.
I previously mentioned this in tips for creating Graph diagrams and it got a mention in What is in your Mathematica tool bag?.
An good example, with a nice bite-sized and digestible bit of code is Experimental`AngularSlider[] mentioned in Circular/Angular slider. I'll leave it up to you to look at the code produced.
Another example is something like BoxWhiskerChart, where you need to call it once in order to load all of the code. Then you see that BoxWhiskerChart proceeds to call Charting`iBoxWhiskerChart which you'll have to unprotect to look at, etc...
I'm looking for an application to display what a linq expression would do, in particular regarding the usage of multiple access to the same list in a query.
Better yet, the tool would tell if the linq query is good.
I used the expression tree visualizer in the past to at least help decode what is inside of an expression tree. It aids in figureing out the parts of the tree and how gives each part is related.
Well, to begin with, I could easily foresee a tool that would pick a query apart and detect that the Where-clause is the standard runtime implementation, and thus not examine that method, but "know" what the execution plan for that method would be, and could thus piece together a plan for the whole query.
Right up until the point where you introduce a custom Linq provider, where the only way to figure out what it will be doing would be to read the code.
So I daresay there is no such tool, and making one would be very hard.
Would be fun to try though, at least for standard classes, would be a handy debugging visualizer for Visual Studio.
What about making the tool yourself?! ;)
Take a look at Expression trees, I believe they might be useful
When adding internationalisation capabilities to an Oracle web application (build on mod_plsql), I'd like to interpret the HTTP_ACCEPT_LANGUAGE parameter and use it to set various NLS_* settings in the Oracle session.
For example:
HTTP_ACCEPT_LANGUAGE=de
alter session set nls_territory=germany;
alter session set nls_lang=...
However, you could get something more complicated I suppose...
HTTP_ACCEPT_LANGUAGE=en-us,en;q=0.5
How have folks tackled this sort of thing before?
EDIT - following on from Curt's detailed answer below
Thanks for the clear and detailed reply Curt. I didn't really make myself clear though, as I was really asking if there were any existing Oracle widgets that handled this.
I'm already down the road of manually parsing the HTTP_ACCEPT_LANGUAGE variable and - as Curt indicated in his answer - there are a few subtle areas of complexity. It feels like something that must have been done many times before. As I wrote more and more code I had that sinking "I'm reinventing the wheel" feeling. :)
There must be an existing Oracle approach for this - probably something in iAS??
EDIT - stumbled across the answer
While looking for something else, I stumbled across the UTL_I18N package, which does exactly wham I'm after:
Is there an easy way to convert HTTP_ACCEPT_LANGUAGE to Oracle NLS_LANG settings?
Sure, and it's not too tough, if you break up the problem properly and don't get to ambitious at first.
You need, essentially, two functions: one to parse the HTTP_ACCEPT_LANGUAGE and produce a language code, and one to take that and generate the appropriate set commands.
The former can get pretty sophisticated; if you're given only 'en', you probably want to generate 'en-us', you need to deal with chosing one of multiple choices when nothing matches perfectly, you need to deal with malformed header values, and so on. Don't try to tackle this all at once: just do something very simple at first, and extend it later.
The same more or less goes for the other half of it, generating the set commands, but this is pretty simple in and of itself anyway; it's really just a lookup function, though it may get a bit more sophisticated depending on what is provided to it.
What will really make or break your programming experience on something like this is your unit tests. This is an ideal problem for unit testing and test-driven development. Unit tests will make sure that when you change things, old functionality keeps working, and make it easier to add new functionality and fix bugs, because you just add another test and you have that to guide you from that point on. (You'll also find it easier to do a complete rewrite of one of the functions if you find out you've gone terribly wrong at some point, because you can easily confirm that the new version isn't breaking anything.)
How you do unit testing in your environment is probably a bit beyond the scope of this question, but let me add a few hints. First, if there's a unit test framework ("pl-sql-unit?") available for your environment, that's great. If not, don't panic. You don't need anything sophisticated: just a set of inputs and expected outputs, and a way to run them through the function and either say "all OK!" or show any incorrect results. You can probably write a single, simple PL/SQL function that reads the inputs and expected outputs from a table and does this for you.
Finally stumbled across the answer. The Oracle package UTL_I18N contains functions to map from the browser language codes to Oracle NLS settings:
utl_i18n.map_language_from_iso;
utl_i18n.map_territory_from_iso;
The mapping doesn't seem to cope very well with multi-language settings, e.g. en-us,en;q=0.5, but as long as you just use the first 5 characters the functions seem to work ok.
HTTP_ACCEPT_LANGUAGE: ar-lb,en-gb;q=0.5
v_language:
v_territory:
HTTP_ACCEPT_LANGUAGE: ar-lb
v_language: ARABIC
v_territory: LEBANON