Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[miauw62]

Yeah, I fixed them all.
I couldn't figure out how to forward-declare those template functions (im never going to use two-dimensional arrays again btw, these templates are only necessary because of them but i can't be arsed to rewrite it) so I just moved them up, and replaced the switch with an else-if chain, which is incredibly hacky but works.

[Reelya]

Being more specific wouldn't work - when it first encounters "block" it has no context for what you are calling a block - it could be a variable name, a class, a typedef, a macro etc, pretty much anything that can be given a name. You can't assume that the compiler will know what sort of syntax element you mean. Often when we say we'd like a more specific error message it relies on our meta-knowledge of the program's intent which the compiler does not possess.

When it says "int assumed" it's saying it's read "block" to be a variable name, and it attempts to instantiate it as "int block" by default. That makes the * bit following it to be a syntax error. By default the compiler assumes unfamiliar names are variables.

"block *tet;" could be a pointer variable of type "block". but remember * is also multiplication, so "block *tet;" is also a completely valid c++ statement of variable "block" times variable "tet". So, the compiler has no way of knowing whether you forgot to declare two variables which are being multiplied, or you forgot to declare a type which is getting a pointer.

Theoretically, the compiler could be designed to do look-ahead in all source files in the project, just in case the unfamiliar name in one cpp file is a type defined somewhere else, and some scripting languages do allow that. But it would be a fucking amazingly shit way to do things on large or complex projects - every typo could add several minutes to the compile time while it works out that you just had a spelling mistake and weren't referring to some class somewhere.

[miauw62]

I understand how it works, I was just being dumb and forgot that it's a good idea to declare them at the start of your file to avoid headaches.

[Thief^]

Later languages like C# have been designed so that they can be 2-pass compiled, i.e. it is extremely obvious from the language grammar when a word is a type that just hasn't been encountered before, because there's nothing else it could be. Which means the source can be parsed once looking for types variables and functions etc, and then again to actually compile code. Unfortunately C++ is an ancient language in comparison, and a lot of its problems are issues inherited from C. Needing forward declarations may be fixed with the C++ "modules" proposal being worked on at the moment for a future version of C++ (possibly C++17).

Re: templates:
1: You don't need them:

Code: [Select]

void clear_box(int inputarr[5][5])
{
for (int i = 0; i < 5; i++)
{
for (int j = 0; j < 5; i++)
{
inputarr[i][j] = 0;
}
}
}
Works perfectly.

2:
When you wrote this:

Code: [Select]

template <int height, int width>
void copy_array(int from[][height], int to[][width])
you probably meant:

Code: [Select]

template <int height, int width>
void copy_array(int from[height][width], int to[height][width])

3: When you use "<" in a for loop's condition, it excludes its end value.
So when you wrote this:

Code: [Select]

for (int i = 0; i < height - 1; i++)you are looping from 0 to up to and not including 4 (height - 1 == 4). You either mean "< height" or "<= height - 1"

[Gentlefish]

No it includes 4. 4 is the last run because 4 < 5 resolves. 5< 5 does not resolve true and therefore is a good way to iterate over an array of length 5 (0 - 4).

[Thief^]

Did you miss the "- 1" in his code?

[Reelya]

The original source code reads:

for (int i = 0; i < height - 1; i++)

If "height" is 5, then this will loop 0-3, which is clearly a mistake.

[Gentlefish]

Wait. I'm confused.

for (int i = 0; i < height - 1; i++)

If "height" is 5, then this will loop 0-3

This is what I'm getting. You'd want

for (int i = 0; i <= height - 1 ; i++)

which is just more keystrokes.

[Thief^]

Or "for (int i = 0; i < height ; i++)" (without the "- 1"). Like I said.

[Reelya]

Wait. I'm confused.

for (int i = 0; i < height - 1; i++)

If "height" is 5, then this will loop 0-3

This is what I'm getting. You'd want

for (int i = 0; i <= height - 1 ; i++)

which is just more keystrokes.

Just take the -1 off and have it "< height" would fix it. I don't think you're processing what we're discussing, which is someone else's faulty code.

miauw62 also has lines that loop from "0" to "<4" for a 5-dimensional array. I think he's systematically missing the last iteration of every loop.

[Gentlefish]

Yes that is true D: I'm very confused and will wait patiently until next discussion.

[DreamThorn]

@Pufferfish:
Step-by-step explanation:

X x[h];
This creates an array with h elements, indexed from 0 to h-1.

for (int i = 0; i < h-1; i++) {};
This loops from 0 to h-2, because when (i == h-1), the (i < h-1) test fails and it exits from the loop immediately.

If you want to include all the elements, it should be (i < h).

@EveryoneElse:
GitHub mystifies me.  I forked a project, but now I'm stuck.
1. Which is the right way to get the code to my machine so that I can make changes and send them back to my fork?
2. The original project has had other changes made in the meantime, so how do I get my fork up-to-date?

I'm sure I'll have more questions later, when I'm less mystified. 

[Thief^]

1. GitHub has a client now which is the easiest way to download/upload from a github repository. Otherwise you need to learn how to operate Git.

[Orange Wizard]

1. Git's Windows client is terribad. I recommend using something like Git Extensions, which has various options and not everything is a bloody square.

[DreamThorn]

Thanks, I'll take a look.