Abstract question. Is there "data decorator" bundle for Symfony2? Or how would you solve elegantly data localization/formatting problems?
For example:
float - decimals formatting, monetary data needs monetary formatting
integers - formatting - 1'000'000 vs 1.000.000
dates, times
etc
I know that Symfony1 had some kind decorating going on in templates which would suit this exactly. It wasn't perfect, though and arised other problems.
Anybody knows, is there something? Or what would be the "correct" way for solving this problem?
Your question as it stands is too vague and answers can be considered primarily opinion-based, but you're aware that the native PHP functions do everything that you're asking for, right?
Float, integer formatting: number_format
Date/Time formatting: DateTime class and its subsequent format functions
Twig even uses the equivalent functions to achieve exactly what you're asking for: number_format and the date filters.
This would be the correct standard - and although I have literally no experience with Symfony1, I haven't had any issue deploying a dozen Symfony2 projects using just these two functions to achieve the data decorating that you desire.
Related
I'm trying to understand the pros/cons and when to use the various encoding options that are available to me in h2o with the parameter 'categorical_encoding'.
It would be helpful if people could point out general rules of thumb on how to use this.
Typically I use the 'Enum' value because I like how all categorical values are grouped together when looking at feature importance. On the other hand, xgboost's default value is 'label-encoder' I believe, which breaks things up by categorical level/value.
Unfortunately, I don't really know where to begin or questions to ask around these other values available:
one hot internal
one hot explicit
sort_by_response
enum_limited
enum
-label-encoder
Again, I primarily stick with enum, sometimes label-encoder, but honestly I don't know practical implications of these various options. Would love a generalized understanding of when one might be better than other from someone knowledgeable !
As requested (thanks!) this question was reposted to cross-validated. So the answer on what the pros and cons are can be found at: https://stats.stackexchange.com/questions/376203/categorical-encoding-in-h2o-what-is-the-difference-between-the-options
In PL-SQL, there are some fancy new concepts, like table functions, objects, and probably others I have not discovered yet.
But then again, there is also plain simple code generation (dynamic pl-sql) that you can "execute immediately".
These can help with code reuse.
From what I can tell, table functions and objects can help with creating modular code, but still not enough to remove the entire of it (maybe I am not using the best of them; I have to admit my objects only contain data for now and no logic).
On the other side, the code generating is much more simple, and can reduce duplicate code more. But it is kind of hard to read what the actual business is behind the code generation logic.
I want modular and not-duplicate code. Should I stick with plain code generation? What are some pros and cons of each?
Dynamic SQL is generally better than advanced PL/SQL features like table functions, object-relational types, data cartridge, the ANY* types, etc. With a few simple tips you can avoid the pitfalls of dynamic SQL and use it to create modular systems.
Advanced PL/SQL features are cool, and at some point you'll have to use them at least a little. They're great for solving weird, specific problems. But you will almost certainly regret creating an Oracle system that is centered around one of those features. I've wasted weeks or months of my life on each of the above PL/SQL features.
Dynamic SQL
Pro - It always works. It might be painful, but there's always a way to make it work in SQL and make it run fast.
Con - A little harder to read and write.
Advanced PL/SQL
Pro - Cool features, elegant code that can perfectly solve certain problems.
Con - Will let you down at a critical moment.
It's hard to give examples of advanced PL/SQL failures without writing a novel. The stories typically go something like this: "We combined features A, B, C ... we hit bugs X, Y, Z ... everyone got angry ... we spent a month re-writing it."
Dynamic SQL doesn't have to be so bad. It just takes some discipline.
Good formatting and instrumenting. Make sure the dynamic SQL looks beautiful and it can be easily printed out for debugging. Follow good programming practices - indent, add comments, use meaningful names, etc. It will be a shock to the point-and-click programmers when the "Beautifier" button on the IDE doesn't help them. Don't let anyone get away with sloppy code - just because it's technically a string shouldn't allow anybody to avoid common style rules.
Alternative quoting mechanism. Use the q syntax to avoid constantly escaping things. For example, q'[I'll use single quotes if I want to!]' instead of 'I''ll use single quotes if I want to!'.
Templates instead of concatenation. Write the code in un-interrupted blocks and then replace the dynamic parts later. Combine it with the q strings to avoid a million quotation marks and pipes in the code. For example:
v_dynamic_sql_template constant varchar2(32767) :=
q'[
select a, b, $DYNAMIC_SELECT_LIST$
from table1
$DYNAMIC_JOIN_1$
where table1.a > 1
$DYNAMIC_WHERE_1$
]';
...
v_dyanmic_sql := replace(v_dynamic_sql_template, '$DYNAMIC_SELECT_LIST$', v_variable);
...
(In this question I assume you are an intermediate or advanced Oracle developer. If you're a beginner, the answer is probably static SQL statements but you haven't
seen enough SQL features to realize that yet.)
I've been looking for a proper implementation of hash map in R, with functionalities similar to the map type in Python.
After some googling and searching the R documentations, I found that environment and named list are the ONLY options I can use (is that really so?).
But the problem with the two is that they can only take charaters as key for the hashing, not even a number, let alone other type of things.
So is there a way to use arbitrary things as key? or at least more than just characters.
Or is there a better implemtation of hash map that I didn't find with better functionalities ?
Thanks in advance.
Edit:
My current problem: I need a map to store the distance relationship between data points. That is, the key of the map is a tuple (p1, p2) and the value is a number.
The reason I asked a generic question instead of a concrete one is that I'm learning R recently and I want to know how to manipulate some of the most fundamental data structures, not only what my problem refers to. So I may need to use other things as key in the future, and I want to avoid asking similar questions with only minor difference every time I run into them.
Edit 2:
I got a lot of very good advices on this topic. It seems I'm still thinking quite in the Pythonic way, rather than the should-be R way. I should really get more R-ly ! I think my purpose can easily be satisfied by a matrix in R. Thanks All !
The reason people keep asking you for a specific example is that most problems for which hash tables are the appropriate technique in Python have a good solution in R that does not involve hash tables.
That said, there are certainly times when a real hash table is useful in R, and I recommend you check out the hash package for R. It uses environments as its base but lets you do a lot of R-like vector work with them. It's efficient and I've never run into a problem with it.
Just keep in mind that if you're using hash tables a lot while working with R and your code is running slowly or is buggy, you may be able to get some mileage from figuring out a more R-like way of doing it :)
I'm a bit of a polyglot when it comes to programming languages, and most of the languages I use have Error/Exception handling of some sort.
In most languages there's a default implementation of error ID's with their associated messages, but I've never found a list of production codes to base my own error codes off of.
Does such a thing exist?
If not would it be useful, or just noise that most programmers ignore?
The closest thing I can think of is POSIX error constants (though their numeric values are not standardized.)
Short answer - no, it doesn't exist. Every OS, platform and piece of software pretty much has its own error IDs. These are not synchronized or based on any standard set.
I would say that apart from the common errors, this would indeed just be noise, and even with the common one, one one need to standardize them and ensure they are used universally.
I'm writing some children's Math Education software for a class.
I'm going to try and present problems to students of varying skill level with randomly generated math problems of different types in fun ways.
One of the frustrations of using computer based math software is its rigidity. If anyone has taken an online Math class, you'll know all about the frustration of taking an online quiz and having your correct answer thrown out because your problem isn't exactly formatted in their form or some weird spacing issue.
So, originally I thought, "I know! I'll use an expression parser on the answer box so I'll be able to evaluate anything they enter and even if it isn't in the same form I'll be able to check if it is the same answer." So I fire up my IDE and start implementing the Shunting Yard Algorithm.
This would solve the problem of it not taking fractions in the smallest form and other issues.
However, It then hit me that a tricky student would simply be able to enter most of the problems into the answer box and my expression parser would dutifully parse and evaluate it to the correct answer!
So, should I not be using an expression parser in this instance? Do I really have to generate a single form of the answer and do a string comparison?
One possible solution is to note how many steps your expression evaluator takes to evaluate the problem's original expression, and to compare this to the optimal answer. If there's too much difference, then the problem hasn't been reduced enough and you can suggest that the student keep going.
Don't be surprised if students come up with better answers than your own definition of "optimal", though! I was a TA/grader for several classes, and the brightest students routinely had answers on their problem sets that were superior to the ones provided by the professor.
For simple problems where you're looking for an exact answer, then removing whitespace and doing a string compare is reasonable.
For more advanced problems, you might do the Shunting Yard Algorithm (or similar) but perhaps parametrize it so you could turn on/off reductions to guard against the tricky student. You'll notice that "simple" answers can still use the parser, but you would disable all reductions.
For example, on a division question, you'd disable the "/" reduction.
This is a great question.
If you are writing an expression system and an evaluation/transformation/equivalence engine (isn't there one available somewhere? I am almost 100% sure that there is an open source one somewhere), then it's more of an education/algebra problem: is the student's answer algebraically closer to the original expression or to the expected expression.
I'm not sure how to answer that, but just an idea (not necessarily practical): perhaps your evaluation engine can count transformation steps to equivalence. If the answer takes less steps to the expected than it did to the original, it might be ok. If it's too close to the original, it's not.
You could use an expression parser, but apply restrictions on the complexity of the expressions permitted in the answer.
For example, if the goal is to reduce (4/5)*(1/2) and you want to allow either (2/5) or (4/10), then you could restrict the set of allowable answers to expressions whose trees take the form (x/y) and which also evaluate to the correct number. Perhaps you would also allow "0.4", i.e. expressions of the form (x) which evaluate to the correct number.
This is exactly what you would (implicitly) be doing if you graded the problem manually -- you would be looking for an answer that is correct but which also falls into an acceptable class.
The usual way of doing this in mathematics assessment software is to allow the question setter to specify expressions/strings that are not allowed in a correct answer.
If you happen to be interested in existing software, there's the open-source Stack http://www.stack.bham.ac.uk/ (or various commercial options such as MapleTA). I suspect most of the problems that you'll come across have also been encountered by Stack so even if you don't want to use it, it might be educational to look at how it approaches things.