I've seen some code written like this:
if (true) {
... // do something
}
Why would you want to do something like this? Is there any thing special about this structure?
THanks
Pretty much any modern compiler would just optimize this away. My guess is that someone put it there during development to let them easily remove a block of code (by changing true to false), and either forgot or didn't bother to remove it when they were done.
This is one of many ways to segment out code during testing/development. Many might debate whether or not it is good coding practice, but it can be a quick and handy way to compartmentalize code. It is also a quick way to execute code that follows a complex conditional statement that you want to test.
Might be able to use it like this:
/* if (my_comlex_or_rare_conditional_case) then */
if (true) then
{
lots of code here....
} /*End if */
There have been times where I've added true || or false && inside a condition to force it to execute the branch and test the code - but only during development. The code you've posted doesn't need the if condition.
Related
New programmer here,
How would I convert this while loop to a for loop?
while(continue()){
printf("test")
}
You wouldn't, really, the while loop is the best construct for that particular use case. A for loop has a setup step, continuation condition, and post-iteration step, and you only need the second of those (which is what while uses anyway).
But, if you really wanted to do this, it would be something like:
for(;continue();)
It's not something I, or probably any sane person, would do :-)
Most of people would prefer while in this case, but for would look like this:
for(;continue();)
{
printf("test");
}
I've been drawing a sequence diagram of a module recently, while reverse engineering.
I encountered a control statement, and it is like,
if (func_A() == True)
{
DoSomeThing();
}
else
{
DoSomeThingElse();
}
The problem is how to draw the condition?
As I mentioned, It is reverse engineering. The code cannot be modified now.
I drew two diagrams, and I don't know which way is right,
The first one is this, I think it's wrong because it doesn't show the function call as a message from A to B.
This is the second, It shows a message func_A.
What do you think about to do this right?
To complete the other answer there is anyway a problem in the second proposal because we do not know if in [func_A() == True] you reuse the value return by the previous call or you do a second call, to avoid that add the explicit return in your diagram :
Out of that do you know the activities ? A sequence diagram is "just" an interaction while an activity is a behavior and can be more adapted :
It depends. If func_A is an operation defined in Object2 the second representation would be correct. The first does not tell where the operation is defined. Most likely (!) one would interpret func_A as an operation local to ObjectA which your code seems to say. (Btw. you have two completely different object sets AB vs. 12 in your examples.) But that is uncertain. So the 2nd variant is more explicit (and correct).
In any case I advise to not overdo SDs with fragments as "graphical programming" doesn't make things easier to read (my practical experience). It's excellent to show message flows in various collaborations. But when it comes to conditions it's getting messy very soon. A better way is to create different sub-diagrams or even use pseudo code if there are too nested if conditions. In many cases such if clauses are a good fit for state machines.
How do you make a breakable loop in Scratch? I'm using Scratch 2.0 and can't find any good way to make a loop breakable, from inside of the loop itself.
Disclaimer:
There is no perfect way to do it. If you can possibly stand this true fact then feel free to continue.
There are a few different ways you could do it.
With repeat until
The first and most simple one follows this:
But this isn't technically part of the script - it's just repeating until some value returns true.
With a custom block (stop this script)
In order to do it inside of the script, you'll need to use a sneaky little trick with custom blocks.
Create a custom block called whatever you want - but probably along the lines of "breakable loop". Inside of it, create this script:
By using stop script we are breaking out of the script that is currently running - which, according to Scratch, is the custom block.
See the result! (as scratchblocks)
With broadcast and wait
You could also use a broadcast-and-wait method, very similar to above:
Though I highly suggest you don't use this method, as if any other sprites have breakable loops you'll need to rename each one, which can be tedious after using a lot of loops in a lot of sprites!
(Note this bug has been fixed in version 442 of the editor and such the following no longer applies.)
Help! My project is lagging a bunch now!
As #foi has noticed, if your code must be run inside of a frame you probably checked run without screen refresh. Unfortunately, due to a bug in the Scratch player, this causes the program to essentially break after the stop this script block has been activated. How can you handle this?
It follows the same principle you use when you use a run without screen refresh custom block inside of a forever loop - the loop doesn't use screen refresh while the inside does, allowing for instant animations whether or not one is using turbo mode.
Here's an example - the image is really too long to be embedded, so see it here instead.
You can make a variable inside or outside of the repeat and make your script like this:
repeat until [[my variable] = [e.g: 1]]
your code
your code
your code
your code
end of repeat until
For a "repeat until" block the simplest way would be to "or" your normal until condition with the break condition in the until.
By adding an incremeting loop counter variable in the loop you can use a "repeat until" to replicate the function of a "repeat n times" block
By using a "repeat until" block with only your break condition you get the equivalent of a "forever" block
If you need another script/ sprite to trigger the break then a public variable will let you break the loop from anywhere and let a single condition break loops for different sprites.
I'd post an image of the blocks but this is my first reply and the site won't let me!
good luck
You can use these few ways to do it...
conditional loop
stop this script
if then else, in the else section, put nothing
I would prefer to use the first method, as it requires less blocks and for the first method, you can still add in code that will be executed after the loop has stopped executing.
You can make it repeat x times or make it have a certain point where it stops, such as another variable changing.
Otherwise, I don't think there is a wat to do that.
Use the repeat until block. Then put in an equals block or whatever into the boolean part. Then inside that repeat until block, put a stop this script block.
Hope this helps :D
I´m trying to draw an UML activity diagram for a fnction that is (highly simplified) represented by the following code snippet. My intention is to have a subactivity for the lines that check the mode parameter (if-else).
ErrorType DoSomething(int mode) {
if(mode==MODE1) {
...
}
else {
return MODE_NOT_AVAILABLE;
}
SomethingElse...
return NO_ERROR;
}
You can see, the return-Statement in the else-Block leads to termination of function DoSomething. So if it´s executed, there is no way for SomethingElse... to be executed.
As I mentioned, this else-block should be in a subactivity.
How do I visualize that an action in a subactivity (return MODE_NOT_AVAILABLE) has the consequence that it´s parental activity diagram has to be in a final state?
In the following picture you can see my try to solve it. Is this a correct solution?
Since you are dealing with some kind of exception, I'd model it with an exception handler like you see here http://www.sparxsystems.com.au/images/screenshots/uml2_tutorial/ad11.GIF. Even though your concrete implementation uses if/else, that should be a way which makes it easy to understand what you want to achieve (prevent the subroutine from being executed in wrong mode).
You can see more details about the notation here: http://edn.embarcadero.com/article/30169
It depends on how much you want to dictate the actual implementation. UML itself is langage-unaware, and so are most stakeholders.
This question already has answers here:
Closed 13 years ago.
Possible Duplicates:
Formatting of if Statements
Is there a best coding style for identations (same line, next line)?
Best way to code stackoverflow style 'questions' / 'tags' rollover buttons
public void Method {
}
or
public void Method
{
}
Besides personal preference is there any benefit of one style over another? I used to swear by the second method though now use the first style for work and personal projects.
By readability I mean imagine code in those methods - if/else etc...
Google C++ Style Guide suggests
Return type on the same line as function name, parameters on the same line if they fit.
Functions look like this:
ReturnType ClassName::FunctionName(Type par_name1, Type par_name2) {
DoSomething();
...
}
WebKit Coding Style Guidelines suggests
Function definitions: place each brace on its own line.
Right:
int main()
{
...
}
Wrong:
int main() {
...
}
They suggest braces-on-same-line for everything else, though.
GNU Coding Standards suggests
It is important to put the open-brace that starts the body of a C function in column one, so that they will start a defun. Several tools look for open-braces in column one to find the beginnings of C functions. These tools will not work on code not formatted that way.
Avoid putting open-brace, open-parenthesis or open-bracket in column one when they are inside a function, so that they won't start a defun. The open-brace that starts a struct body can go in column one if you find it useful to treat that definition as a defun.
It is also important for function definitions to start the name of the function in column one. This helps people to search for function definitions, and may also help certain tools recognize them. Thus, using Standard C syntax, the format is this:
static char *
concat (char *s1, char *s2)
{
...
}
or, if you want to use traditional C syntax, format the definition like this:
static char *
concat (s1, s2) /* Name starts in column one here */
char *s1, *s2;
{ /* Open brace in column one here */
...
}
As you can see, everybody has their own opinions. Personally, I prefer the Perl-ish braces-on-same-line-except-for-else, but as long as everybody working on the code can cooperate, it really doesn't matter.
I think it is completely subjective, however, I think it is important to establish code standards for your team and have everyone use the same style. That being said I like the second one (and have made my team use it) because it seems easier to read when it is not your code.
In the old days we used to use the first style (K & R style) because screens were smaller and code was often printed onto this stuff called paper.
These days we have big screen and the second method (ANSI style) makes it easier to see if your brackets match up.
See HERE and HERE for more information.
First one is smaller in terms of number of lines (maybe that is why development -Java- books tend to use that syntax)
Second one is, IMHO easier to read as you always have two aligned brackets.
Anyway both of them are widely used, it's a matter of your personal preferences.
I use the if statement as something to reason on in this highly emotive subject.
if (cond) {
//code
}
by just asking what does the else statement look like? The logical extension of the above is:-
if (cond) {
//code
} else {
//more code
}
Is that readable? I don't think so and its just plain ugly too.
More lines is != less readable. Hence I'd go with your latter option.
Personally I find the second one more readable (aligned curlys).
Its always easiest for a team to go with the defaults, and since Visual Studio and I agree on this, thats my argument. ;-)
Your lines of code count will be considerably less with the first option. :)