Programming Forums > Application Development > C#

Arla · May 12th, 2005, 7:06 PM

So I have the following code

if (i==1)
  Long J = 10;
else
  Long J = 20;

System.Console.Writeline("J is {0}",J);

And I get a compile error, since J seems to only be valid inside of the If statement? Is that really true, do you have to create this as

(Toggle Plain Text)

Long J;
if (i==1)
  J = 10;
else
  J = 20;

System.Console.Writeline("J is {0}",J);

(I know it's a trivial example, but I'm trying to understand if this is something I'm doing wrong, or really the way it's supposed to work).

new User(Kevin.Parkinson) · May 12th, 2005, 10:45 PM

Arla:
I would generally follow the principle that if something is only declared within curly braces, for example:

(Toggle Plain Text)

if( thisIsTrue )
{
     int a = 9;
}
else
{
     int a = 10;
}

...then that variable( in this case int a ) will go out of scope and thus not be available outside of those curly braces. so, to answer your question:

(Toggle Plain Text)

Long J;
if (i==1)
  J = 10;
else
  J = 20;

System.Console.Writeline("J is {0}",J);

...as you said yourself, this will work for you, and is the right way to use J!

Arla · May 13th, 2005, 11:50 AM

Okay, just wanted to check, seems a bit odd compared to other languages I've worked with, but then again, they all have there oddities right!

Ooble · May 13th, 2005, 1:08 PM

It's so you can declare a variable in, for example, a loop, and declare it again in another one. For example:

(Toggle Plain Text)

for (int i = 0; i < 10; i++)
{
    Console.WriteLine ("{0}\n", i);
}

for (float i = 0; i < 1; i += 0.05)
{
    Console.WriteLine ("{0}\n", i);
}

Infinite Recursion · May 16th, 2005, 9:11 AM

I also had to jump this hurdle when I was first exposed to C#.

spydoor · May 16th, 2005, 12:12 PM

hmm, my experience is this is usually true.

a variable declared within a block is only usable within that block.

I'm just curious.. what langauges don't behave this way?

Ooble · May 16th, 2005, 1:04 PM

C is a good example. You also can't declare variables within if/for/while/do-while statements in C.

HeX · May 16th, 2005, 1:20 PM

It's the same in Java

Berto · May 17th, 2005, 3:18 AM

Yeah i learned all this from java, then went to C and realised i cant initilise a variable in the for loop brackets :/,

Just look up scope of variables on good ole' google to help you out a bit more.

HeavyMetal · May 21st, 2005, 8:48 PM

c'mon people, it's called a scope, it's like a vision thing, what you declare in a function, or a statement,stays on the inside. it's one of the basics of C#

May 12th, 2005, 7:06 PM	#1
Arla Hobbyist Programmer Join Date: Mar 2005 Posts: 227 Rep Power: 4	Code annoyance, variables not available outside of if statements? So I have the following code (Toggle Plain Text) if (i==1) Long J = 10; else Long J = 20; System.Console.Writeline("J is {0}",J); if (i==1) Long J = 10; else Long J = 20; System.Console.Writeline("J is {0}",J); And I get a compile error, since J seems to only be valid inside of the If statement? Is that really true, do you have to create this as (Toggle Plain Text) Long J; if (i==1) J = 10; else J = 20; System.Console.Writeline("J is {0}",J); Long J; if (i==1) J = 10; else J = 20; System.Console.Writeline("J is {0}",J); (I know it's a trivial example, but I'm trying to understand if this is something I'm doing wrong, or really the way it's supposed to work).

May 12th, 2005, 10:45 PM	#2
new User(Kevin.Parkinson) Programmer Join Date: Mar 2005 Location: Edmonton, Alberta, Canada Posts: 37 Rep Power: 0	Arla: I would generally follow the principle that if something is only declared within curly braces, for example: (Toggle Plain Text) if( thisIsTrue ) { int a = 9; } else { int a = 10; } if( thisIsTrue ) { int a = 9; } else { int a = 10; } ...then that variable( in this case int a ) will go out of scope and thus not be available outside of those curly braces. so, to answer your question: (Toggle Plain Text) Long J; if (i==1) J = 10; else J = 20; System.Console.Writeline("J is {0}",J); Long J; if (i==1) J = 10; else J = 20; System.Console.Writeline("J is {0}",J); ...as you said yourself, this will work for you, and is the right way to use J! __________________ (Toggle Plain Text) public class MySignature extends Post implements JavaSyntax throws NuttinHoney{ MySignature() { Salutation(); Name(); } public string Salutation() { Screen.printLn( "Sincerely,\n" ); } public string Name() { Screen.printLn( "Kevin Parkinson" ); } } public class MySignature extends Post implements JavaSyntax throws NuttinHoney{ MySignature() { Salutation(); Name(); } public string Salutation() { Screen.printLn( "Sincerely,\n" ); } public string Name() { Screen.printLn( "Kevin Parkinson" ); } } Last edited by new User(Kevin.Parkinson); May 12th, 2005 at 10:55 PM.

May 13th, 2005, 1:08 PM	#4
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	It's so you can declare a variable in, for example, a loop, and declare it again in another one. For example: (Toggle Plain Text) for (int i = 0; i < 10; i++) { Console.WriteLine ("{0}\n", i); } for (float i = 0; i < 1; i += 0.05) { Console.WriteLine ("{0}\n", i); } for (int i = 0; i < 10; i++) { Console.WriteLine ("{0}\n", i); } for (float i = 0; i < 1; i += 0.05) { Console.WriteLine ("{0}\n", i); } __________________ Me :: You :: Them

May 16th, 2005, 9:11 AM	#5
Infinite Recursion Programming Guru Join Date: Jul 2004 Location: United States Posts: 3,467 Rep Power: 8	I also had to jump this hurdle when I was first exposed to C#. __________________ http://jasonpowers.net "There are a thousand hacking at the branches of evil to one who is striking at the root."

May 16th, 2005, 1:04 PM	#7
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	C is a good example. You also can't declare variables within if/for/while/do-while statements in C. __________________ Me :: You :: Them

May 13th, 2005, 11:50 AM	#3
Arla Hobbyist Programmer Join Date: Mar 2005 Posts: 227 Rep Power: 4	Okay, just wanted to check, seems a bit odd compared to other languages I've worked with, but then again, they all have there oddities right!

May 16th, 2005, 12:12 PM	#6
spydoor Programmer Join Date: Feb 2005 Posts: 64 Rep Power: 4	hmm, my experience is this is usually true. a variable declared within a block is only usable within that block. I'm just curious.. what langauges don't behave this way?

May 16th, 2005, 1:20 PM	#8
HeX Programmer Join Date: May 2005 Location: Kosova Posts: 94 Rep Power: 4	It's the same in Java __________________ (Toggle Plain Text) countdown++; countdown++;

May 17th, 2005, 3:18 AM	#9
Berto Programming Guru Join Date: Aug 2004 Posts: 1,022 Rep Power: 6	Yeah i learned all this from java, then went to C and realised i cant initilise a variable in the for loop brackets :/, Just look up scope of variables on good ole' google to help you out a bit more. __________________ "Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute. THAT'S relativity." - Albert Einstein

May 21st, 2005, 8:48 PM	#10
HeavyMetal Newbie Join Date: May 2005 Posts: 5 Rep Power: 0	c'mon people, it's called a scope, it's like a vision thing, what you declare in a function, or a statement,stays on the inside. it's one of the basics of C# __________________ The Code Lord

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Programming Forums > Application Development > C#

Code annoyance, variables not available outside of if statements?