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I'm getting Expected expression errors on the following code:
(void) for(t; t < kPlatformsStartTag + kNumPlatforms; t++) { //error here
CCSprite *platform = (CCSprite*)[batchNode getChildByTag:t];
CGSize platform_size = platform.contentSize;
CGPoint platform_pos = platform.position;
max_x = platform_pos.x - platform_size.width/2 - 10;
min_x = platform_pos.x + platform_size.width/2 + 10;
float min_y = platform_pos.y + (platform_size.height+bird_size.height)/2 - kPlatformTopPadding;
if(bird_pos.x > max_x &&
bird_pos.x < min_x &&
bird_pos.y > platform_pos.y &&
bird_pos.y < min_y) {
[self jump];
}
}
(void) for(t; t < kCloudsStartTag + kNumClouds; t++) { //error here
CCSprite *cloud = (CCSprite*)[batchNode getChildByTag:t];
CGPoint pos = cloud.position;
pos.y -= delta * cloud.scaleY * 0.8f;
if(pos.y < -cloud.contentSize.height/2) {
currentCloudTag = t;
[self resetCloud];
} else {
cloud.position = pos;
}
}
The error is found where the "for" code is. I put the (void) code in because I will get an Expression result unused error. Any ideas?
The (void) before the for loop does not make sense.
You have to remove the (void) before the for loop because it's not a valid c syntax. You can't solve an error with another error.
You may ask the question : Why puting (void) before the for loop prevented the unused expression error. Well that's because the debugger didn't reach it. and it doesn't know for what is for as he expected a resulted value from it to cast it to void.
When the compiler is generating the error: Unused Entity Issue - Expression result unused. That's means that your program is evaluating an expression without using it.
In your case at the for loop if the t variable is already initialized as you want it, you shouldn't put it at the first part as it will be considired as an unused expression.
for(; t < kPlatformsStartTag + kNumPlatforms; t++) { // keep the first expresion empty
// ...
}
You've already got answers about the bogus (void), but not about the unused expression.
for(t; t < kCloudsStartTag + kNumClouds; t++)
The initial expression here, t, has absolutely no effect, and for that reason has no business being present at all. The value of t is read and immediately discarded, and any decent compiler will optimise that by not even bothering to read t. You do not need an expression here. You can remove it, and write
for(; t < kCloudsStartTag + kNumClouds; t++)
although personally, I might be tempted to go with a while loop instead.
Edit: reading your code more closely, your code seems to need to give t an initial value.
for(t = 0; t < kCloudsStartTag + kNumClouds; t++)
Either way, your attempt to suppress the warning without understanding what the warning was telling you wasn't a good idea.
Related
This question already has answers here:
Removing from array during enumeration in Swift?
(9 answers)
Closed 6 years ago.
In this loop we have the potential to reduce the number of items in the loop while processing it. This code works fine in Obj-C, but the Swift loops don't get the message that an item has been removed and end up overflowing the array.
In Objective-C, we had:
for(int i = 4; i < staticBlocks.count; i++)
{
PlayerSprite* spr = [staticBlocks objectAtIndex:i];
[spr setPosition:CGPointMake(spr.position.x, spr.position.y-1)];
if(spr.position.y < -1000)
{
[staticBlocks removeObject:spr];
[spr removeFromParent];
}
if(spr.blockTypeIndex == Block_Type_Power_Up)
{
[spr update];
}
}
In Swift I know of these options:
//for i in 4.stride(to: staticBlocks.count, by: 1){ //crashes
//for i in 4..<staticBlocks.count{ //crashes
for var i = 4; i < staticBlocks.count; i += 1 { //works, but is deprecated
let spr = staticBlocks.objectAtIndex(i) as! PlayerSprite
spr.position = CGPointMake(spr.position.x, spr.position.y-1)
if(spr.position.y < -1000)
{
staticBlocks.removeObject(spr)
spr.removeFromParent()
//break
}
if(spr.blockTypeIndex == k.BlockType.PowerUp)
{
spr.update()
}
}
In this specific case, it really isn't a problem for me to use a break statement (which is currently commented out) to kill the loop and prevent the crash, but it doesn't seem like the proper fix. I assume there will come a time when I need to know how do do this correctly. Is there a non deprecated way to do a for loop, one which processes the count each pass?
A related, unanswered question.
Is the for loop condition evalutaed each loop in swift?
I don't know how to link to a specific answer, but this code did what I needed. Marking as duplicate now.
Removing from array during enumeration in Swift?
var a = [1,2,3,4,5,6]
for (i,num) in a.enumerate().reverse() {
a.removeAtIndex(i)
}
This is because in Swift you cannot remove items from an array while you are iterating over it.
From this question Removing from array during enumeration in Swift?
you can see that you should be using the filter function instead of using a for loop.
For example, don't do this:
for (index, aString: String) in enumerate(array) {
//Some of the strings...
array.removeAtIndex(index)
}
Do something like this:
var theStrings = ["foo", "bar", "zxy"]
// Filter only strings that begins with "b"
theStrings = theStrings.filter { $0.hasPrefix("b") }
(Code example from this answer)
Additionally, it should be noted that filter won't update the array, it will return a new one. You can set your array to be equal to that array afterwards.
An additional way to solve the issue, from the same question is to do this:
var a = [1,2,3,4,5,6]
for (i,num) in a.enumerate().reverse() {
a.removeAtIndex(i)
}
print(a)
Closed. This question needs debugging details. It is not currently accepting answers.
Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 7 years ago.
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So im trying to code a function to remove an element from an Array.for some reason i'm getting no errors but still does not print the result i need. i think the problem is in the function or data type declaration.
#import <Foundation/Foundation.h>
void deleteArray(char stra[ ], char ElementToRemove);
int main(int argc, const char * argv[]) {
#autoreleasepool {
char str[100];
printf("Please Enter Array Elements\n");
scanf("%s",&str);
deleteArray(str, "a");
printf("%s",&str);
}
return 0;
}
void deleteArray(char stra[ ], char ElementToRemove)
{
int NumberOfElements = sizeof(stra);
int ElementPos;
for (int i = 0; i >= NumberOfElements;i++)
{
if (ElementToRemove == stra [i])
{
ElementPos = i;
}
}
for (int SecondCounter = ElementPos; SecondCounter >= NumberOfElements;SecondCounter++ )
{
stra[SecondCounter] = stra[SecondCounter - 1];
}
}
There are many issues with your code, let's see them one by one.
When you pass an array to a function, it decays to a pointer to the first element of the array. So, sizeof in the deleteArray() function is not doing what you think it's doing there.
You can use strlen() instead to get the length of a char array. However, please note, this does not count the terminating null, anyways, and you need to move that one, too, to make the end of the modified array.
Then, in the for loop,
for (int i = 0; i >= NumberOfElements;i++) //false always....
is wrong. I believe what you want is
for (int i = 0; i < NumberOfElements;i++)
After that, regarding the call to the function should be
deleteArray(str, 'a'); // 'a' is a char
instead of
deleteArray(str, "a"); // "a" denotes a string
Next, in the main() function, remove the & from the argument to printf(). It should look like
printf("%s",str);
Also, to ensure safety from buffer overflow, you should make yourscanf() to look like
scanf("%99s",str);
If you need dynamically sized arrays, I recommend making them the last flexible array member (that wikipage has an example) of some (growable) struct and keep the size of that array in its containing struct ....
If you want to have array features, such as add, delete, move and so on, use linked lists. Linked lists are using pointers, so you can represent an array using them. This way it is possible to delete an element, move it or add a new one.
When declaring an array in c, you declare it fixed size. In your case, if you want not to use pointers and lists, you have to copy array elements to a new one, excluding the unneeded.
-(void)updateCharacterStatsForArmor:(RKArmor *)armor withWeapons:(RKWeapon *)weapon withHealthEffect:(int)healtheffect
{
if (armor != nil){
self.character.health = self.character.health - self.character.armor.health + armor.health;
self.character.armor = armor;
}
else if (weapon != nil){
// The problematic line:
self.character.damage = self.character.damage - self.character.weapon.damage + weapon.damage;
self.character.weapon = weapon;
}
else if (healtheffect != 0){
self.character.health = self.character.health + healtheffect;
}
else {
self.character.health = self.character.health + self.character.armor.health;
self.character.damage = *(self.character.damage + self.character.weapon.damage);
}
}
#end
The line with the error is marked in the code snippet. The error says invalid operand to binary expression int int*.
Would It be best to restart the whole thing?
You probably defined one of the damage properties you're using as an int* instead of int. Check your character and weapon classes for that. I'd suspect self.character.damage.
If the line you indicated really is the problem, it looks like you've probably declared the damage property of the character class to return int * instead of int. It's easy to make that mistake because properties that point to objects are always pointers. int, however, is not an object type, so there's usually not need to store a pointer to one in a property.
The line you say is a problem is:
self.character.damage = self.character.damage - self.character.weapon.damage + weapon.damage;
But later on you have:
self.character.damage = *(self.character.damage + self.character.weapon.damage);
It looks like this second line is some kind of attempt to avoid a compiler error, but it doesn't seem to make a lot of sense. You'd only dereference the result of the addition if you were doing pointer arithmetic, but that doesn't make much sense for a property called damage.
To fix all this, take a look at your character class declaration. You'll probably see something like:
#property(...) int *damage;
Remove that * and make sure the attribute is assign, like this:
#property(assign) int damage;
Also, it's not clear how pirates are involved. Perhaps ye have been a mite hasty in makin' yer query? Arrr!
-(void)InitWithPwd:(char *)pPwd
{
char szResult[17];
//generate md5 checksum
CC_MD5(pPwd, strlen(pPwd),&szResult[0]);
szResult[16] = 0;
m_csPasswordHash[0]=0;
for(int i = 0;i < 16;i++)
{
char sz[3] = {'\0'};
//crash in blow row. The first pass is ok. The third pass crash.
//I can't understand.
sprintf(&sz[0],"%2.2x",szResult[i]);
strcat(m_csPasswordHash,sz);
}
m_csPasswordHash[32] = 0;
printf("pass:%s\n",m_csPasswordHash);
m_ucPacketType = 1;
}
I want to get the md5 of the password. But above code crash again and again. I can't understand why.
Your buffer (sz) is too small, causing sprintf() to generate a buffer overflow which leads to undefined behavior, in your case a crash.
Note that szResult[1] might be a negative value when viewed as an int (which happens when passing a char-type value to sprintf()), which can cause sprintf() to disregard your field width and precision directives in order to format the full value.
Here is an example showing this problem. The example code is written in C, but that shouldn't matter for this case.
This solves the problem by making sure the incoming data is considered unsigned:
sprintf(sz, "%02x", (unsigned char) szResult[i]);
I am trying to compare a CGFloat to an integer value. Based on this value, execute a conditional... pretty standard. However, this will always be true for some reason. I even print out the values and they are clearly less than 800.... I have tried a bunch of different combinations, the most recent is shown below, I thought maybe it was comparing the size of float and the size of the int based purely on its binary values, so I tried this risky little cast operation... Any ideas?
CGPoint textViewPoint = [scroller convertPoint:[textView center] toView:(UIView *)self.view];
NSLog(#"the y coord is %f", textViewPoint.y);
int size = (int)textViewPoint.y;
NSLog(#"the yint %d", size);
//move the main view, so that the keyboard does not hide it.
//if (self.scroller.frame.origin.y >= 0 && textViewPoint.y > 800.0);
if(size > 800);
{
NSLog(#"moving up");
The problem is the ; at the end of the if(size > 800); line, not the int vs. float comparison. Remove it and all should be OK.
This is because this semicolon is interpreted as the body of your if statement, and that's this NO-OP statement that is executed when the condition is true. Then, the rest of your code next to this if empty body is outside of the if body so is executed whatever the condition value. That's exactly as if you had written:
if(size > 800)
{
}
{
NSLog(#"moving up");
}
Compiler Warning Tip
The compiler generally warns you about this mistake. Be sure that you have the "Empty Loop Bodies" warning activated in your project Build Settings (compiler flag -Wempty-body): this way the next time you do this mistake, you will have a warning about it and will know what is wrong and how to fix it.