I will first describe the problem and then what I currently look at, in terms of libraries.
In my application, we have a set of variables that are always available. For example: TOTAL_ITEMS, PRICE, CONTRACTS, ETC (we have around 15 of them). A clients of the application would like to have certain calculations performed and displayed, using those variables. Up until now, I have been constantly adding those calculations to the app. It's pain in the butt, and I would like to make it more generic by way of creating a template, where the user can specify a set of formulas that the application will parse and calculate.
Here is one case:
total_cost = CONTRACTS*PRICE*TOTAL_ITEMS
So, want to do something like that for the user to define in the template file:
total_cost = CONTRACTS*PRICE*TOTAL_ITEMS and some meta-date, like screen to display it on. Hence they will be specifying the formula with a screen. And the file will contain many formulas of this nature.
Right now, I am looking at two libraies: Spirit and matheval
Would anyone make recommendations what's better for this task, as well as references, examples, links?
Please let me know if the question is unclear, and I will try to further clarify it .
Thanks,
Sasha
If you have a fixed number of variables it may be a bit overkill to invoke a parser. Though Spirit is cool and I've been wanting to use it in a project.
I would probably just tokenize the string, make a map of your variables keyed by name (assuming all your variables are ints):
map<const char*,int*> vars;
vars["CONTRACTS"] = &contracts;
...
Then use a simple postfix calculator function to do the actual math.
Edit:
Looking at MathEval, it seems to do exactly what you want; set variables and evaluate mathematical functions using those variables. I'm not sure why you would want to create a solution at the level of a syntax parser. Do you have any requirements that MathEval does not fulfill?
Looks like it shouldn't be too hard to generate a simple parser using yacc and bison and integrate it into your code.
I don't know about matheval, but boost::spirit can do that for you pretty efficiently : see there.
If you're into template metaprogramming, you may want to have a look into Boost::Proto, but it will take some time to get started using it.
Related
I have inherited a large base of SAS code. I need to reverse engineer to create some mapping document, so that given a field in the final output dataset, we can easily trace it all the way back to one of the inputs.
I can create it by hand, but can SAS automatically generate something like this?
No, I don't think there is any ready-made automated way of doing this.
Bear in mind that it is possible to create variables and pass them through a whole series of procs and data steps without mentioning them by name anywhere in the source code. Some sort of run-time analysis is therefore unavoidable.
Reeza's suggestion of using proc scaproc will yield some useful information for code executed within a single self-contained job running in a single SAS session, and the ATTR option in the record statement might be of some help to you when tracing the lineage of variables, but I'm afraid that however you approach this, it's going to take quite a lot of work.
What are some good resources/examples for good coding patterns to follow in RShiny applications?
I feel I am following two bad patterns in the shiny applications I am creating.
To make things react to user changes properly, I seem to end up wrapping most parts of server.r in observe().
At the beginning of each observe(), I want the expression to rerun if any one of a whole bunch of inputs change.
Ideally, I would like to put input[change_set] where change_set is a character vector of input names, however this gives an error of Error in [.reactivevalues: Single-bracket indexing of reactivevalues object is not allowed.
(or if I use input[[change_set]]: Error in checkName: Must use single string to index into reactivevalues)
What I end up doing to make things work is including multiple lines of input$var1, input$var2, ..., input$var15. This feels very wrong.
I am not making use of any functions like: reactive(), reactiveValues(), isolate(), withReactiveDomain(), makeReactiveBinding(), ... . I am guessing that I probably should be, but I don't know how to use them.
The solution to this problem is likely to be me rereading the small print in the documentation and reading code from example applications. Does anybody know any good quality resources for this?
I got this list of items (it's in a sql script) and I would like to reorder it by number :
from this :
,user_1
,user_2
,user_3
,name_1
,name_2
,name_3
to this
,user_1
,name_1
,user_2
,name_2
,user_3
,name_3
I use sql server management studio 2008 so I have ability to replace using regex but I don't know if that kind of manipulation is even possible with regular expressions.
Just copy paste them in excel, then sort and then copy paste back to ssms.
It's that simple :)
I think you need to add a bit more description for this to really make sense.
Perhaps post the SQL script?
Is this data stored in a single varchar field and this is the reason you are looking for a regex solution?
You can easily parse the comma-seperated values using a regex, but you would need some other function to sort that result and it can fairly quickly get messy to do this in SQL.
In general I would say this problem is better handled outside of the SQL statement - eg. process this in your favorite programming/scripting language after getting the result back from the SQL.
Also this problem indicates a design problem with the database layout, if in any way possible the preferred way to solve this would probably be to restructure it.
In a nutshell, I want to have different faces for some types of file in dired mode. I don't think it matters, but I am using Aquamacs.
The example I will use here is .tex files. If I can do it for .tex, then I can just apply the same structure to do create other faces for other types of files.
From what I understand, I have to create a variable, write a regular expression, then apply a hook. I read a bit about regex and so far I have
^(.+)\.tex$
I think my structure and regular expression are not really correct. I am not a programmer (though I have an interest on it), I have only been using Emacs for 2 weeks or so, so any help would be greatly appreciated.
What I need is at least the basic structure of what I have to do. I understand there may be modes already created that do something similar (such as maybe Wdired and Dired-X), and I would not complain if someone told me about them, but what I really want is to have an elisp code (either already written or that I can work on), as I plan on learning a bit of elisp to be able to write my own customisations and this would be a way to learn.
Thank you!
Since you want to learn how to do it, try checking out the extension dired+.el. This mode does a lot more than what you want, but it does add new faces. Specifically, look for the variable diredp-font-lock-keywords-1 and how it is used. That should get you going.
Other SO questions that seem relevant are:
Match regular expression as keyword in define-generic-mode
Highlighting correctly in an emacs major mode
A hello world example for a major mode in emacs?
I have inherited a large legacy ColdFusion app. There are hundreds of <cfquery>some sql here #variable#</cfquery> statements that need to be parameterized along the lines of: <cfquery> some sql here <cfqueryparam value="#variable#"/> </cfquery>
How can I go about adding parameterization programmatically?
I have thought about writing some regular expression or sed/awk'y sort of solution, but it seems like somebody somewhere has tackled such a problem. Bonus points awarded for inferring the sql type automatically.
There's a queryparam scanner that will find them for you on RIAForge: http://qpscanner.riaforge.org/
There is a script referenced here: http://www.webapper.net/index.cfm/2008/7/22/ColdFusion-SQL-Injection that will do the majority of the heavy lifting for you. All you have to do is check the queries and make sure the syntax will parse properly.
There is no excuse for not using CFQueryParam, apart from it being much more secure, it is a performance boost and the best way to handle quoted values in character based column types.
Keep in mind that you may not be able to solve everything with <cfqueryparam>.
I've seen a number of examples where the order by field name is being passed in the query string, which is a slightly trickier problem to solve as you need to validate that in a more "manual" way.
<cf_inputFilter
scopes = "FORM,COOKIE,URL"
chars = "<,>,!,&,|,%,=,(,),',{,}"
tags="script,embed,applet,object,HTML">
We used this to counteract a recent SQL injection attack. We added it to the Application.cfm file for our site.
I doubt that there is a solution that will fit your needs exactly. The only option I see is to write your own recursive search that builds a report for you or use one of the apps/scripts that people have listed above. Basically, you are going to have to edit each page or approve all of the automated changes.