Defining equations with a constant

Question

I am trying to define a constant that would have the following in it

ch[co].gold < 10000*100

how can I make it, something like

define x = ch[co].gold < 10000*100;

so that every time I write

if (x) {say(cn,"You need 10 000 gold coins");}

Or that is not possible?

Yes, it's called a boolean expression - just change "define" to a suitable type, e.g. `bool` or `int`. I recommend picking a [book from this list](http://stackoverflow.com/q/562303/253056) and doing some reading if you want to learn C properly. — Paul R, May 24 '16 at 08:01
Thank you everyone, that notation threw me off, was a dumb question but yet something that is i am unfamiliar with in C. Thanks. — Night, May 24 '16 at 08:22
@Night there's a tradeoff here: you can type less now and scratch your head more later ... or type a little more now and keep a clear head in the future :-) — pmg, May 24 '16 at 08:22

score 2 · Answer 1 · answered May 24 '16 at 08:01

2

Function:

int x(int val) {
    return (val < 10000 * 100);
}

Usage

    // ...
    if (x(ch[co].gold)) {
        printf("You need 10 000 gold coins.\n");
    }
    // ...

answered May 24 '16 at 08:01

pmg

106,608
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2

`x()` could have a better name, for example `enoughgold()`. – pmg May 24 '16 at 08:04

score 1 · Answer 2 · answered May 24 '16 at 08:07

1

Well, here is my solution

struct s {
    int gold;
};

const int co = 2;

struct s ch[] = {112,2321,3234};

#define x() ch[co].gold < 10000*100

int main(){
if (x()) {

}
return 0;
}

answered May 24 '16 at 08:07

Roman Podymov

4,168
4
30
57

This one takes the cake. Nicely done, however what i posted is an excerpt from a code, ch[co].gold extracts an int from a structure, and just compares it to 10000*100. So simply asking how and if it is possible to simplify that comparison down to one character instead of typing it out (or ctrl c + ctrl v in that manner) – Night May 24 '16 at 08:14

score 0 · Answer 3 · answered May 24 '16 at 08:13

0

Is this what you are expecting?

#define x (ch[co].gold < 10000*100)

Add this line of code before the place you use it, usually it's just below the #includes. Conventionally, we use capital letters with clearer meanings instead of x.

answered May 24 '16 at 08:13

elricfeng

364
1
8

score 0 · Answer 4 · answered May 24 '16 at 08:15

#define is simply text substition performed by the preprocessor.

To do what you say you want use the following #define:

#define x ch[co].gold < 10000*100

Every time the preprocessor encounters the symbol x it will replace it with ch[co].gold < 10000*100.

I think that what you really want is to make it a proper function as suggested by pmg. It is a wiser choice.

Defining equations with a constant

4 Answers4