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general C question

 
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Dima49



Joined: 11 Apr 2005
Posts: 5

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general C question
PostPosted: Mon Dec 26, 2005 1:40 pm     Reply with quote

hi all,

I've got a genearal C question here (bit of a noob question)

Here are 2 snippets of code where I am defining a structure and then creating an array of the said structure.

Numero Uno:

Code:
typedef struct
//hold variables used for controlling each individual LED in this structure
{
   short fadeDirection;      //indicate if LED fading up or down
   int fadeSpeed;            //speed of LED fading
   int fadeSpeedCount;         //counter used for each individual LED in BREATH mode
   int pwmDuty;            //length of the duty (on time of an LED)
   int ledMask;            //bits of PORTA or B that needed to be masked out to turn on the
                        //particular LED
}LED_PARAMS;

//populate array used to control all LEDs with initial states of all of the vars
LED_PARAMS LEDcontrol[NUM_LEDS]=
{
   {UP, 200, 0, 0, 0b00000001},
   {UP, 19, 0, 0, 0b00000010},



Numero Dose:

Code:
struct
//hold variables used for controlling each individual LED in this structure
{
   short fadeDirection;      //indicate if LED fading up or down
   int fadeSpeed;            //speed of LED fading
   int fadeSpeedCount;         //counter used for each individual LED in BREATH mode
   int pwmDuty;            //length of the duty (on time of an LED)
   int ledMask;            //bits of PORTA or B that needed to be masked out to turn on the
                        //particular LED
}LED_PARAMS;

//populate array used to control all LEDs with initial states of all of the vars
LED_PARAMS LEDcontrol[NUM_LEDS]=
{
   {UP, 200, 0, 0, 0b00000001},
   {UP, 19, 0, 0, 0b00000010},






As soon as I take typedef out the compiler spits out the following error:

Code:


*** Error 48 "C:\cygwin\home\d\pic_dir\fade_code\fade_code.c" Line 52(12,22): Expecting a (
*** Error 43 "C:\cygwin\home\d\pic_dir\fade_code\fade_code.c" Line 52(22,23): Expecting a declaration


The line num reffers to the begining of array declaration.

From what I understand, not using typedef is a newer way of dealing with structure declaration, but most compilers deal with it well. Furthermore, I have seen snippets on the forum with just struct.

I am just trying to understand more about use of structures and what stupid thing did I do to deserve that errror Smile


THnX in advance for any help


d
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Mon Dec 26, 2005 3:01 pm     Reply with quote

http://www.ecf.utoronto.ca/apsc/courses/ece242f/2004spring/notes-242/notes-general-2.html#struct

http://www.cppworld.com/tutorials/?tutorial=structures
Dima49



Joined: 11 Apr 2005
Posts: 5

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thnx
PostPosted: Tue Dec 27, 2005 10:45 am     Reply with quote

Thnx PCM!

read the examples makes soooo much more sense now.

d
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