error when using typedef struct

Question

I have the following typedef struct

typedef unsigned int NOTE_FREQ;
/*******A_MUSIC_ELEMENT structure****************/ 
typedef struct { 
    NOTE_FREQ frequencyValue; 
    int duration; 
} A_MUSIC_ELEMENT;

Now I want to make an array of A_MUSIC_ELEMENT and with specific values.

A_MUSIC_ELEMENT ZTitleScreen[] = {{60, 20},{80, 50}};

and it compiles fine. but to make things more readable I try to set

int BPM1 = 60;
int BPM2 = 80;
int TIME1 = 20;
int TIME2 = 50;
A_MUSIC_ELEMENT ZTitleScreen[] = {{BPM1, TIME1},{BPM2, TIME2}};

and i get an error saying :

constant expression required

i don't know why since it should be the same thing. i am using windows 8, mplab x IDE, hi tech c compiler. any help to demystify this thanks.

woolstar · Accepted Answer · 2013-11-29 05:01:12Z

4

The value of BPM1 could change so the compiler won't allow it as an argument for the initializer list.

If you want to use named constants, try using enum.

answered Nov 29, 2013 at 5:01

woolstar

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1 Comment

woolstar Over a year ago

In c++11 you have a features called const_exp, but in C you may be stuck with doing HALF_NOTE as a macro.

user1814023 · Accepted Answer · 2013-11-29 05:13:09Z

1

6.7.9 Initialization

     4. All the expressions in an initializer for an object that has static or 
thread storage duration shall be constant expressions or string literals.

Below are the different ways in which you can initialize a structure...

struct date date1= { 9, 5, 1982};           // Initializing structure
struct date date2 = { .day = 9, .month = 5};// Designated initializer
struct date date3 = {0};                    // Initializing all members to 0
struct date date4;
struct date date5 = date1;                  // Initialization using variable

date4.day = 9;      // Member wise initialization
date4.month = 5;    // Member wise initialization
date4.year = 1982;  // Member wise initialization

answered Nov 29, 2013 at 5:13

user1814023

2 Comments

Andre Marin Over a year ago

thanks. where is this from? I only understand the main idea from this. all this static and thread storage stuff I would have to research to understand it

user1814023 Over a year ago

The above statement is from C standard (ISO/IEC 9899:201x). Below code I typed it.

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