How to set 1d array to 2d array element in C

Question

I need something like this:

char font[128][8] = {{0}};

font[0][] = {0, 0b00000000, 0b11111100, 0b00010010, 0b00010010, 0b11111100, 0b00000000, 0};
font[1][] = {...}

But in c99 I get "expected expression before '{' token". Please help.

You can't assign to arrays. Either use initializer lists during initialization, or compound literals and memcpy(), or assign one-by-one in a loop. — user529758
– user529758, Commented May 9, 2013 at 11:13

AusCBloke · Accepted Answer · 2013-05-09 22:11:29Z

1

You can only use an initialiser list ({...}) when declaring the array, that's why you're getting an error. You can't assign a value to an array, which is what font[0] is (a char[]).

You have 3 options:

char font[128][8] = {
  {0, 0b00000000, 0b11111100, 0b00010010, 0b00010010, 0b11111100, 0b00000000, 0};
  {...}
 }

Assign each value to an element in the array individually: font[0][0] = x, ..., font[127][7] = y (ie. using a loop).
memcpy blocks at a time from like a uint64_t (sizeof(font[0]) = 8) or wherever else you can neatly/efficiently store the data.

It's probably also worth noting that binary constants are a C extension, ~~and that char is signed~~ and if you're working with unsigned data you should probably explicitly use unsigned char.

edited May 9, 2013 at 22:11

answered May 9, 2013 at 11:20

AusCBloke

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2 Comments

This isn't my real name Over a year ago

Wait, what? char is signed? Since when? In my version of C, whether or not char is signed is a completely implementation-defined decision.

AusCBloke Over a year ago

@ElchononEdelson: Oh yeah you're right, it should be could.

BLUEPIXY · Accepted Answer · 2013-05-09 11:14:08Z

0

char font[128][8] = {
    {0, 0b00000000, 0b11111100, 0b00010010, 0b00010010, 0b11111100, 0b00000000, 0},//font[0]
    /*{...}*///font[1]
};

answered May 9, 2013 at 11:14

BLUEPIXY

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vCillusion · Accepted Answer · 2013-05-09 11:15:12Z

0

Try it out :

    char font[128][8] = {{0}};  
    char a[8] = {0, 0b00000000, 0b11111100, 0b00010010, 0b00010010, 0b11111100, 0b00000000, 0};
    //Take array a to store values 

    for(int i = 0;i<8;i++)
    font[0][i] =  a[i];
    //Assign value of a to font

answered May 9, 2013 at 11:15

vCillusion

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