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Consider a text box with auto complete checking for the existence of the char . or [
Brilliant outsource developer sitting far far away writes the following:
private TextOffsets getTextOffsets(string text, int caretIndex)
{
var heirarchyChars = HeirarchyChars.ToArray();
int previousSeparatorOffset = -1;
if (caretIndex > 0)
{
previousSeparatorOffset = text.LastIndexOfAny(heirarchyChars, caretIndex - 1, caretIndex);
}
...
And of course commits the change... 10 minutes after update contracts kick-in in run time and
ContractException was unhandled
Precondition failed: this == String.Empty || startIndex - count >= 0
Then I go  Update and get this
private TextOffsets getTextOffsets(string text, int caretIndex)
{
var heirarchyChars = HeirarchyChars.ToArray();
int previousSeparatorOffset = -1;
try
{
if (caretIndex > 0)
{
previousSeparatorOffset = text.LastIndexOfAny(heirarchyChars, caretIndex - 1, caretIndex);
}
}
catch (Exception x)
{
}
...
Absolutely brilliant. Let's not fix it.. let's circumvent it... 
By this time curses in Greek are being launched...
Next day update and...
private TextOffsets getTextOffsets(string text, int caretIndex)
{
var heirarchyChars = HeirarchyChars.ToArray();
int previousSeparatorOffset = -1;
int count = caretIndex - 2;
if (caretIndex > 0 && count > 0 )
{
previousSeparatorOffset = text.LastIndexOfAny(heirarchyChars, caretIndex - 1, count);
}
...
 what the...
Pen and paper just to make sure I am not hallucinating... yep we always go back one to check one character forward... Also we have an innovation... one would start an expression for a struct or an array with a . or a [ from position 0 without a variable first. Just brilliant...
Oh well... it should at least be...
private TextOffsets getTextOffsets(string text, int caretIndex)
{
var heirarchyChars = HeirarchyChars.ToArray();
int previousSeparatorOffset = -1;
if (caretIndex > 1)
{
previousSeparatorOffset = text.LastIndexOfAny(heirarchyChars, caretIndex - 1, 1);
}
...
Alberto Bar-Noy
---------------
“The city’s central computer told you? R2D2, you know better than to trust a strange computer!”
(C3PO)
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Nice development environment you have there. Somebody offshore can commit a change that immediately hits production without going through test environment, not bothering with code review, your offshore idiot remains hired... (You are saving $ not paying somebody local, breakdowns of your application reduces costs of running the system for no customers because it doesn't work...)
I'm not too sure about you...
Alberto Bar-Noy wrote: yep we always go back one to check one character forward...
That's for?:
Alberto Bar-Noy wrote: previousSeparatorOffset = text.LastIndexOfAny(heirarchyChars, caretIndex - 1, count);
If caretIndex==10, count would be 8, the start of looking in the array is at 9. If text is a 5 character string, you are allowing the search to start 5 characters past the first valid index location. Same situation, except the string is 10 characters long. You can only look 1 character ahead, yet you are asking for 8, that will blow with the original error you got. (The string has to be 18 characters long or longer for that to work.)
Your statement to look only 1 character forward doesn't make sense either. Going from where you start to the end of the string makes sense to me. Why you are going back 1 character from the index passed doesn't make sense to me either. I'd want to use the last index found to find the next index to be found.
Here's an alternate version:
private TextOffsets getTextOffsets(string text, int caretIndex)
{
var heirarchyChars = HeirarchyChars.ToArray();
var cnt = heirarchyChars.Count();
var strt = caretIndex + 1;
int NewIndex = -1;
if (strt < cnt)
{
NewIndex = text.LastIndexOfAny(heirarchyChars, strt, cnt - strt);
}
Pass in 9 for the starting index for a 10 character string, cnt is 10, strt is 10, doesn't check the string at all.
Of course, since I'm perfect,  I'll go ahead and check this in without even seeing if it will compile...
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well this code never reached production' This is what I was hired for... to kick them out. This code tries to check if the last character typed was . or [
this is an autocomplete for structs and arrays on a PLC Dev. system's only the last char needs to be checked. And in WPF the caret position is after the last character. Finally because of politics (they got their notice so they are still around till Jan. first and I can't fully touch their code.
Alberto Bar-Noy
---------------
“The city’s central computer told you? R2D2, you know better than to trust a strange computer!”
(C3PO)
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Why pass an index field at all? Get the count, subtract 1, use that as the first integer and 1 as your second. If you can't get rid of the field, ignore it and do the same thing.
Don't know enough about WPF, but a string is a string and the caret is either the last character, earlier than the last, or doesn't exist in the string.
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I know! Politics! I can't touch it yet 
Alberto Bar-Noy
---------------
“The city’s central computer told you? R2D2, you know better than to trust a strange computer!”
(C3PO)
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Sorry, it's late, I'm not thinking straight. I can't think of a way to find the length of a string other than text.ToCharArray.Count()
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Int32 contador;
contador = (Int32)0;
and a store procedure with +/- 2600 lines.
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The declaration and initialisation could of course have been done in one line, but that makes little difference. From this I get the impression that the developer who wrote this is very 'modern'. He probably has no idea what the compiler will generate from those simple code lines and added the type cast just in case this assignment might be problematic.
Ironically, assingning zero to a variable of a numeric type is the most unproblematic case of all, since it turns out to be one or more zero bytes, no matter if we are looking at an integer type, a floating point type, signed or unsigned. The compiler knows the size (in bytes) of the variable the value is assigned to and there are no special ways to represent the number 'zero'. Therefore no special type information is needed in the assignment.
Bottom line: I see this as clumsy code, but not as a real horror. It does what it is supposed to and I see no potentially harmful side effects. However, I would also see it as an indicator that the developer should perhaps learn more about what happens under the hood, even if that's not 'modern'.
And from the clouds a mighty voice spoke:
"Smile and be happy, for it could come worse!"
And I smiled and was happy
And it came worse.
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I think, someone may well correct me, that the compiler will ignore the second line as it is repeating the prior step because .net initialises all numbers to zero if no value is explicitly supplied.
Panic, Chaos, Destruction. My work here is done.
Drink. Get drunk. Fall over - P O'H
OK, I will win to day or my name isn't Ethel Crudacre! - DD Ethel Crudacre
I cannot live by bread alone. Bacon and ketchup are needed as well. - Trollslayer
Have a bit more patience with newbies. Of course some of them act dumb - they're often *students*, for heaven's sake - Terry Pratchett
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No. You would get the 'use of an unassigned variable' error and it would not compile.
Edit: To be precise: I made two assumptions:
1) This variable is declared inside a method, not as a class member. Initializing it separately leaves no other possibility than that.
2) If you declare a variable inside a method and don't initialize it, it's still ok for the compiler as long as you don't try to use it in the following code. Such an unused declaration would only trigger a compiler warning. The error would occur as soon as you tried to use the uninitialized variable (other than initializing it) in the following code.
And from the clouds a mighty voice spoke:
"Smile and be happy, for it could come worse!"
And I smiled and was happy
And it came worse.
modified 22-Nov-11 6:03am.
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Generally, you're right. The exception for that rule is if you declare an int array. It will then initialize every int in the array to 0. Kind of nice that you don't have to go through every row in the array to begin with.
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No that's not true, it only zeroes out the array if you create it, not if you declare it. If you declare it, there is no array, just a variable that could hold it. So there's nothing to zero.
And the array would still have to satisfy the rules of definite assignment. (not its elements of course, which is what you seem to be talking about)
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I was thinking in terms of int[] num = new int[10]; not int[] num;
You're agreeing with me that the 10 ints in the first case will all be zero.
if (num == null) would be true in the latter case because there isn't any value types to compare.
if (num[0] == null) would blow up because the array doesn't exist, I don't think it would compile because a value type can't be null.
I don't think that first "if" would work if you declared int num;
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Uninitialized local variables actually aren't null, but uninitialized. So you can't do if (num == null) if you didn't initialize num, you would get "Error: Use of unassigned variable 'num'".
You actually can compare an int with null, that just gives a warning that it's always false.
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There is a difference between local and declared variables. int IS set to zero here:
bool isEmpty = false;
int[] num;
bool isEmpty2;
int num2;
private void SetEndElement(bool strt, bool outer, bool vert)
{
if (num == null) isEmpty = true;
if (num2 == null) isEmpty2 = true;
The following produces 2 warnings and 2 errors and won't compile
Warning 1 The variable 'isEmpty' is assigned but its value is never used ... (stats on where the error is)
...
Error 3 Use of unassigned local variable 'num' ...
private void SetEndElement(bool strt, bool outer, bool vert)
{
bool isEmpty = false;
int[] num;
bool isEmpty2;
int num2;
if (num == null) isEmpty = true;
if (num2 == null) isEmpty2 = true;
So we're both wrong. 
harold aptroot wrote: warning that it's always false.
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KP Lee wrote: So we're both wrong.
I don't see how you got to this conclusion.
Maybe I have to make it clearer.
- statically uninitialized local variables can not be used.
- comparing an int with null gives a warning that it's always false.
- the thread was about local variables.
- fields in a class are not called "declared variables", but are implicitly set to default(T).
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harold aptroot wrote: - comparing an int with null gives a warning that it's always false.
That statement is where you are wrong. It NEVER says that. At least on my compiler.
With local variables, that results in a fatal error (using uninialized local variables) Absolutely no warning about the comparison. See my prior post for the exact error msg.
If YOUR compiler gives THAT warning, I appologize, I assumed you were using a Microsoft compiler. One new enough to compile (var x = "tst";) I definitely will not vouch for all versions.
harold aptroot wrote: - fields in a class are not called "declared variables", but are implicitly set to default(T).
POE TAE TOE/ PAW TAW TOE
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Well, what code are you using?
I'm talking about something like this:
int x = 0;
if (x == null) ;
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CDP1802 wrote: Ironically, assingning zero to a variable of a numeric type is the most unproblematic case of all, since it turns out to be one or more zero bytes, no matter if we are looking at an integer type, a floating point type, signed or unsigned.
That's definitely true of assigning 0 to a variable. But there's a related case that's problematic:
sqlParams.Add(new SqlParameter("Quantity", 0));
Acutally assigns the "Quantity" parameter a value of null, because apparently this fits the definition for
SqlParameter(string parameterType, SqlDbType dbType) better than it does for
SqlParamter(string parameterType, object value) because 0 is a valid value for the enum SqlDbType and any match is a better match than object.
To assign a value of 0, you have to do:
sqlParams.Add(new SqlParameter("Quantity", Convert.ToInt32(0)));
(as for why you would do this... well, I'd rather not go into it...)
So maybe the original coder was confused by that very specific case? ...probably not...
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Ironically, assingning zero to a variable of a numeric type is the most unproblematic case of all, since it turns out to be one or more zero bytes, no matter if we are looking at an integer type, a floating point type, signed or unsigned. The compiler knows the size (in bytes) of the variable the value is assigned to and there are no special ways to represent the number
assuming you aren't needing to deal with the IEEE arithmetic concepts of +0 and -0
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Where would that apply? Floating point types?
And from the clouds a mighty voice spoke:
"Smile and be happy, for it could come worse!"
And I smiled and was happy
And it came worse.
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That would apply in a 1's comp environment on it's integer type. Certainly not on a Windows OS which is 2's comp like every other system that realized 2's comp is a superior mathematical process.
On 1's comp with a 32 bit integer, -0 is for every bit set to 1. In 2's comp every bit as 1 in a signed integer is always -1
On 1's comp, this is how you get -0:
x=-1
x=x+1
When you print it, you get "0", not "-0", but internally it's still -0.
When you add 1 to -0, it first converts all the bits from 1 to 0 and then because you are changing signs, you add an additional 1 to the number so it becomes 1. -1 + 10 would produce 8 and then add 1 to get 9. You've got that extra step of adding or subtracting 1 to be done every time a mathematical operation changes case in either direction with the one exception of reaching -0.
2's comp uses no additional steps when changing cases
In SQL:
select (-2*1024)*1024*1024
select (2*1024)*1024*1024
will produce -2147483648 in the first result, the second will get the following error:
Msg 8115, Level 16, State 2, Line 2
Arithmetic overflow error converting expression to data type int.
Take out the parens and both fail with the same error.
In C# with type int, both will produce -2147483648 (Assuming checked isn't applied.)
modified 3-Dec-11 6:48am.
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Even then +0 is just "all bits zero". It's just -0 that is slightly odd there.
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harold aptroot wrote: It's just -0 that is slightly odd
Shouldn't it be slightly even? I am aware that there is a school of thought that 0 is neither odd nor even; but it divides by 2 with no remainder.
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Slightly even must also be slightly odd, no? Or are you suggesting that it is part even part neither?
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