Chief Delphi - boolean

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atmaturen

20-12-2004 08:13

boolean

ello all,
i've seen to have forgotten how to declare a boolean variable...
any help would be greatly appriceated.
thanks in advanced.
(wow, my spelling is vile)

Joe Ross

20-12-2004 09:25

Re: boolean

There is no boolean variable type in C. Most people declare it as char (or unsigned char) and use the value 0 for false and 1 (or any value != 0) for true.

Through the use of #defines and typedefs, you can emulate it, though.

Code:

typedef unsigned char bool

#define TRUE 1

#define FALSE 0

Then just use the variable type bool and the values TRUE and FALSE.

Mark McLeod

20-12-2004 09:26

Re: boolean

Quote:

Originally Posted by atmaturen

i've seen to have forgotten how to declare a boolean variable...

There isn't an explicit boolean type.
Typically, you use "char"

atmaturen

20-12-2004 17:40

Re: boolean

do the boolean functions (and & not) work this way?

colt527

20-12-2004 17:48

Re: boolean

I'm not 100% sure if this wouldn't work, but my original thought would be it wouldn't.

char boolVar = 1;

if(boolVar)
{
//Do this
}

but for && and || and != they all work the same:

char var1 = 1;
char var2 = 0;

if(var1 == 1 && var2 != 1)
{
//do this
}

Mike Betts

20-12-2004 17:52

Re: boolean

Quote:

Originally Posted by atmaturen

do the boolean functions (and & not) work this way?

Use this (http://www.lysator.liu.se/c/bwk-tutor.html) as a reference and you should be OK.

Astronouth7303

21-12-2004 17:56

Re: boolean

In reply to previous concerns:
As long as you use the logical operators (&& || !) instead of the bitwise ones (& | ~ ^), you shold be ok.

If you need to use == and !=, I would recomend using one of this macros around the operands (the values being compared).

Code:

// CBOOL Converts to BOOLean

#define CBOOL(val) ((val) ? TRUE : FALSE)

// LOGically EQuivalent

#define LOG_EQ(val1,val2) (CBOOL(val1) == CBOOL(val2))

// LOGically Not EQuivalent

#define LOG_NEQ(val1,val2) (CBOOL(val1) != CBOOL(val2))

jude	28-12-2004 00:28

Re: boolean

You can get rid of the #defines by using an enum:

Code:

typedef enum {TRUE=1, FALSE=0} bool;

There's also a small practical benefit for this approach:

Some compilers will be able to do some extra type-checking against the enum values, and warn you if you accidentily try to do something like "bool b_Var = 5".

Quote:

Originally Posted by Joe Ross

Code:

typedef unsigned char bool

#define TRUE 1

#define FALSE 0

Then just use the variable type bool and the values TRUE and FALSE.

Raven_Writer

28-12-2004 12:49

Re: boolean

Assuming you're using MPLAB/CBOT, I think the #define method would be best. The method to use though is completely based on what makes you happy.

There's honestly countless number of ways to accomplish though. Like I said though, I think the #define method is best *not to mention, very short on the lines side*

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