nielsm posted:

Harokey posted:

I have a constraint (due to gui stuff) that I want a dedicated "GUI" thread to make any gui calls.

I essentially need to be able to send functions over from the "main" thread to the "GUI" thread for the "GUI" thread to call. These functions will have an arbitrary number of arguments, and will often have a return value that I'll want to use in the "main" thread.

What I've done right now, is created a gui_call class, which has a virtual do_work() function. Any real gui_call I have inherits from this base class, and all the parameters are given to the class in the constructor. This is incredibly tedious, and there must be a better way. Often these gui_call's are just one function call (but sometimes they're more). Is boost::bind the correct way to do this instead of what I'm doing right now?

GrumpyDoctor posted:

Is there an idiomatic workaround for the fact that you can't use remove_if on STL maps because you can't reorder them? (Or, if you can, how do you do it?)

brc64 posted:

Unfortunately, this method doesn't seem to work when there are more than two spaces. For example, the input "Testing one." end up comparing "g " and " o" in addition to " ", and an extra space is left in. At least, that seems to be the case, when I through some cout statements into the loop to try to help me debug.

roomforthetuna posted:

It's supposed to be testing "g " and " o", that's not your problem. The problem you have is that when you erase a space you still move your index up one, when you need to check the same position again.

You also go one too far at the end of the loop, because you're looking at string[i+1] when i is the final character - not a big deal in this case since it'll just be a terminating null character, but a thing to be wary of in general.

Jethro posted:

Or you need to change your loop to only increment the index when you don't erase a character.

roomforthetuna posted:

Also, just to catch this early in your learning, apparently it's better to get into the habit of "++i" rather than "i++" for various reasons. I habitually do i++ because I've already been doing it that way for years, but since you haven't, try to form the better habit!

brc64 posted:

I'm not asking for you to do my homework for me, but I could use a bit of help to come up with the right algorithm for this assignment. I feel like I'm close, but I must be missing something simple. The assignment is to take a line of input ending with a '.' and format it so it looks like a proper sentence. Capitalize the first letter, remove extra spaces between words, and make the other letters lowercase. I've got the case stuff down... that's easy, but I'm stuck on the space problem.

roomforthetuna posted:

Also, just to catch this early in your learning, apparently it's better to get into the habit of "++i" rather than "i++" for various reasons. I habitually do i++ because I've already been doing it that way for years, but since you haven't, try to form the better habit!

Jethro posted:

Or you need to change your loop to only increment the index when you don't erase a character.

brc64 posted:

code:

// starting at 1 because the first character is assumed to be a letter

for(int i=1; i<sentence.length(); i++){
     if((sentence[i]==' ') && (sentence[i+1]==' '))
          sentence.erase(i,1);
     }

Ghost Town Perv posted:

Say I have a class and two derived classes

Is it possible to create a single STL vector that holds objects of all three of those types?

nielsm posted:

...
You can also look into using smart pointers instead.

icantfindaname posted:

When I try to compile this code in visual c++ express 2010 on windows 7, it gives me a bunch of syntax errors on the brackets in the sort function:

The errors:

code:

1>quicksort.cpp(9): error C2143: syntax error : missing ')' before 'constant'
1>quicksort.cpp(9): error C2143: syntax error : missing ';' before 'constant'
1>quicksort.cpp(9): error C2059: syntax error : ')'
1>quicksort.cpp(10): error C2143: syntax error : missing ';' before '{'
1>quicksort.cpp(10): error C2447: '{' : missing function header (old-style formal list?)

MutantBlue posted:

Those line numbers (9,10,11,...) aren't actually in your source file are they? I get similar errors if I don't edit out the line numbers.

icantfindaname posted:

I added them to show the lines in the error messages. On second thought, here's the whole program

code:

#define length 16

void sort (int *array1, int length)

icantfindaname posted:

I added them to show the lines in the error messages. On second thought, here's the whole program

code:

#define length 16

void sort (int *array1, int length)
{
	quick (array1, array1 + length - 1);
}

MutantBlue posted:

That #define tells the preprocessor to replace "length" with "16" everywhere it sees it. This makes the next line look like "void sort (int *array1, int 16)" and the "int 16" is where the error is.

nielsm posted:

Lesson to take: Always write macros with uppercase, like LENGTH. Or, since you're actually writing C++ (your file is named .cpp), make a proper constant:

code:

const int length = 16;

MutantBlue posted:

If you're actually writing C++ use std::sort()

nielsm posted:

It looks like it might be some kind of homework or other. The C standard library also has a qsort() function.

nielsm posted:

Lesson to take: Always write macros with uppercase, like LENGTH. Or, since you're actually writing C++ (your file is named .cpp), make a proper constant:

code:

const int length = 16;

A MIRACLE posted:

code:

istream& operator>>(istream&s, const cityinfo_c &city) 

Clobbersaurus posted:

How do you guys handle memory profiling?

I've been trying to use ps -u and valgrind and I've been sort of confused by the output - I know it's sort of naïve to say I want to know 'only' the heap and stack usage - but what values are most accurate for measuring this? What do you look at?

I'm writing a program that needs to be really memory efficient for a large number of entries that each get malloced. I had been using the resident set size field of ps -u, but I think the heap isn't represented by it.

HFX posted:

I use the massif for valgrind. As long as you are using a semi recent version, it should show heap and memory usage and break down where they occured and how much is being used by them. Massif's whole job is memory profiling.

Clobbersaurus posted:

Cool! So if I'm interpreting this correctly - the total heap usage is then the mem_heap_B + mem_head_extra_B?, where the 'extra' is just the overhead on malloc references and heap structure and all that?

HFX posted:

I use the massif for valgrind. As long as you are using a semi recent version, it should show heap and memory usage and break down where they occured and how much is being used by them. Massif's whole job is memory profiling.