Posts by Maniero • 444,682 points
6,921 posts
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viewsA: Does PDO use DBMS syntax or do they all work?
TL; DR You have to rewrite "all" the darlings. Detailing You just asked about the PDO fallacy. It is an abstraction mechanism to the database access API, not the database commands. One of the…
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answer235
viewsA: Accuracy of float64
Rounding occurs with the function math.Round(). But don’t even try to use it to solve the problem you have there. What you want is accuracy and not precision. Binary floating point types are not…
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viewsA: Function that calculates the factorial of a number
There’s a lot of things wrong there. Most variables are unnecessary. When you’re creating code you have to ask yourself what you need it for. If you don’t have an answer don’t use it. If you can’t…
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viewsA: Is Try-with-Resource in PHP?
No, in essence it doesn’t. One that PHP is a language of script Everything runs for a few seconds, at best, usually a fraction of it, so not releasing a resource makes no difference. And even if I…
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answer238
viewsA: How to pass a dynamically allocated struct to a C function?
The basic error is that the parameter is not declared as a pointer. If the local variable was declared with pointer the argument will be a pointer, then the parameter will also be, which makes…
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viewsA: Best way for database normalization
It always depends. But I would say that the most certain is an entity of Pessoa that may even PessoaFisica and PessoaJuridica find it interesting and have other objects with roles that this person…
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viewsA: What is the difference between using toString() and JSON.stringify()?
JSON.stringify() is a function of the object JSON that will create a string of the object within the default adopted by JSON. By a near match (not 100% because JSON is based on JS notation) the…
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viewsA: What is the difference between parseint() and operator + before a string?
Javascript has weak typing, as well as dynamic typing. This means that it does type coercion to try to meet what the programmer had done using as close a criterion as possible, so if the code has an…
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viewsA: How to return the name of an instance of a class?
This is a misconception. First there is no instance name, there is variable name. It may even be that in this case a name is equal to the variable name, but it cannot always represent any name in a…
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viewsA: How to pass a matrix as a reference to a function?
C is a language without many abstractions, so you need to control each aspect directly and do what you don’t want to do or create your own abstractions or mechanism to control it. You can pass the…
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viewsA: Is it always good to de-locate the memory before a "sudden" output of the program with the Exit function call?
See the function documentation exit(). In fact it does some cleaning on when it is called, it can even record some things to be performed when it is called. If you need something to be executed you…
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answer133
viewsA: What is the difference of declaring a variable as constexpr const and constexpr?
constexpr informs the compiler that it has the result of that expression at compile time so it can optimize and solve without taking that to execution. const only ensures that that value will not be…
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viewsA: Formal definition of operations = and ==
It’s very simple, the = is a allocation operator, you should only use it to store a value in a variable. The left-hand operand should always be a variable, nothing more. Already the right operand…
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viewsA: Why is it possible to change an array or object value from within a constant?
Because who is constant is the value placed there in the identifier and, contrary to what people think, the content of this identifier (which seems variable, but we cannot call it so because it does…
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viewsA: Error in Datetime.Tryparse
You have to add the specific culture to the application to know what kind of data it is waiting for, in case I imagine you’re waiting for the Brazilian, then it would be this: using System; using…
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viewsA: How to pass an attribute of the child class through the constructor to the mother class
There are several wrong premises in the question. The first is the misuse of the term attribute. I know, everyone teaches wrong because of the plague that is UML that uses this term. Languages do…
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answer565
viewsA: Function to check that all elements of a variable array are null
Walk the array and check with is_null() if the value is null. If it is not already you can end the execution since one is not null enough to return false. Only if it goes through all the array…
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viewsA: Difference between local variable VS global variable
What is the difference in speed between? No significant. They are pre-allocated. Locations need to move a pointer in register, but the cost is close to zero. Both the local variable and the global…
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viewsA: Validation of string size
Use mb_strlen(). But it’s not that simple. This can be a problem for user usability. It shouldn’t bother you with implementation details. How are you gonna tell him what to do with something he…
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viewsA: Validate input without variable
if int(input("Digite um numero: ")) <= 10: print("Ok, numero registrado") else: print("Numero invalido, digite outro numero menor que 10") Variables are value storage locations, that’s all. You…
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answer295
viewsA: What is the concept of virtual machine? What are the positives and negatives?
I will respond with application VM bias and ignore other types. Virtual machine is a simulation of a real machine through software. Therefore a software is created that will run on the real machine…
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viewsA: How to open an executable that requires elevation via C#?
Second that response in the OS: if (!IsAdministrator()) { // Restart program and run as admin var exeName = System.Diagnostics.Process.GetCurrentProcess().MainModule.FileName; ProcessStartInfo…
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viewsA: Execution error on switch
One of the errors presented is that it is asking wrong formatting on scanf(). I actually think I wanted to ask for the operation character and not a number, so I changed that too. And the syntax of…
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viewsA: Returning(Null) when displaying a String variable
sexo is the type char, ok, just one character to store it, at least in the form used. But there is an error reading it. To read a data char use the %c in the scanf(). Already in the name is using…
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viewsA: Compilation and execution error difference
The overall answer has already been given in What’s the difference between "Compile time" and "run time"?. No matter how it occurs, what matters is that it occurs when the application is running.…
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answer58
viewsA: How to fire multiple errors in a single data check using C#
try { obj.TryGetValue(prop.Name, out temp); prop.SetValue(usuario, Convert.ChangeType(temp, prop.GetType())); } catch (Exception) { throw; } I put in the Github for future reference. This makes no…
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viewsA: What is the name of this structure in Python?
This is called informally f-strings, but the more formal term is interpolation literal of strings. The f there indicates that the following text is a feedback of what will be used, so within it…
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answer82
viewsA: Is it mandatory to list tables in a database?
No, on the contrary. Only engage in relationships where you need to. Do anything only if you can adequately justify it. In fact the most commonly used form of relationships is by JOIN and nothing is…
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answer78
viewsA: How to concatenate values of different types into a string?
I imagine this is what you want: auto equation = to_string(num1) + " " + simbol1 + " ( " + to_string(num2) + " " + simbol2 + " " + to_string(num2) + " ) = ? "; I put in the Github for future…
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viewsA: Python is not so "smart" for redundant operations
One of Python’s philosophies is to make life easier for the programmer It is answered. This is the opposite of what you are concerned about. Perhaps it is a matter of interpreting the text. At least…
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viewsA: Pointers and matrices catching something unexpected
First let’s agree that this code is potentially wrong. It compiles into bad or poorly configured compilers. I wouldn’t try to learn from him. Why the array was declared with empty line subscript int…
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viewsA: Does table order make a difference in modeling?
Why not both? That’s why the database is relational, you make up as you please. This is why it is superior to other models in most cases. Relationship does not involve property but rather link. I…
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viewsA: What’s the difference between throw and Alert
It just happens to behave the same way in this particular code. In fact this is not even required, and in fact Javascript not used in a browser will change for sure. There is zero relationship…
javascriptanswered Maniero 444,682 -
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viewsA: Functions defined within conditional blocks
For those who follow me know that I am critical of good practices, and of course, the bad ones too. I like to understand motivations, have the foundation to do right. And I talk a lot about context.…
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viewsA: Converting C to Java
while in Java we use boolean to say that the condition is true, in this case it uses a char. Tips on how to turn into Java? In C a condition is false when it is 0, any other value is true. That’s…
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viewsA: What is the default visibility of a variable in Typescript, what is the importance of var when declaring variables?
Is public by default. In Typescript, in class members, the var is unnecessary, is adopted the semantics of var even without its explicit use.…
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answer142
viewsA: What are the differences between macros and constexpr? When is it preferable to use one instead of the other?
When it is preferable to use Macro instead of constexpr (and vice versa)? And what are the main differences between these two approaches? Macros in C++? Never! This is not a language resource, it’s…
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viewsA: Two "Return" in a function
I had asked in comment because at first I was too abstract, still remains a little abstract of what you really want, but come on the options. This is not possible. The return has two functions:…
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answer51
viewsA: Time leaving with unexpected result
You want to print the local time and the correct function for this is the localtime(), and not the gmtime() which gives you the universal call time (no time zone). from time import localtime,…
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answer59
viewsA: Why am I only able to manipulate files with pointers?
Because the given that function fopen() returns is a pointer, so you have to declare the variable with a compatible type. If it returns something else, this is what you have to declare in the…
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viewsA: Factorial function does not return
The code is confusing, disorganized and has too many things. But the main problem is mixing concepts without criterion. The statement demonstrates what it has to do. The factorial is a number…
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answer353
viewsA: What are and what are the main differences between Functional Programming and Reactive Programming?
It’s complicated to answer that because it’s like asking what the differences between oranges and beets are. Yeah, both are eating, finished. Functional programming is something that is based on the…
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viewsA: Why does this work? pointer = (struct a *)&b;
I could answer that is because C is a weakly typed language, it tries to make it work, even if it gives unexpected results. But as it is static typing does not accept the type being different, so if…
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answer1151
viewsA: Problem with struct: "Expected Expression before"
There are several errors there and I tried to correct the main ones (I kept some things I would do differently in real case), maintaining a different organization and nomenclature, removing what is…
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answer80
viewsA: Is it possible to include the necessary . NET to run a standalone application?
It is possible to use the .NET Core. It’s also possible as Mono, but this is becoming less and less necessary. The . NET Core has some limitations yet. By 2019 you will no longer have most of them…
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viewsA: How to interpret this line? (struct list*)0)
(struct lista*) is a cast, then the code is telling the compiler to interpret the value below as being of this specified type, i.e., a pointer to a structure called lista previously declared. In…
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viewsA: What are side effects?
The side effect is the phenomenon that interferes in a situation beyond the expected, that happens something as a consequence of the main event. That’s what computing is about, too, and we use it to…
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viewsA: Rename field in a lambda
syn.sol.sol.sol.sol. surely it’s one of the biggest absurdities I’ve ever seen in code and something tells me it shouldn’t stop there, but I think this is what you want: var qry =…