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Marcofras
n00b
Joined: 29 May 2023
Posts: 52
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 Posted: Tue Apr 22, 2025 12:36 pm Post subject: float not precised |
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| Code: |
#include <cstdio>
#include <iostream>
#include <fstream>
#include "colr.hpp"
using namespace std;
int main() {
float di = 200 / 31;
cout << di << endl;
return 0;
}
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the correct result is 6.4516129, in another program i use the result is 3. |
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grknight
Retired Dev
Joined: 20 Feb 2015
Posts: 2120
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| Posted: Tue Apr 22, 2025 12:59 pm Post subject: |
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Try with | Code: | | float di = 200.f / 31; |
Integer division drops the decimal. Including one float should resolve your issue |
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Marcofras
n00b
Joined: 29 May 2023
Posts: 52
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| Posted: Tue Apr 22, 2025 1:06 pm Post subject: |
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now its 6.45161 that is not precised but i can be satisfied.
now i have problem with
| Code: |
if (g == 0) {r1 = 0;} else {r1 = (g * 100) / r;}
if (b == 0) {r2 = 0;} else {r2 = (b * 100) / g;}
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how use the member .f in this expression? |
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logrusx
Advocate
Joined: 22 Feb 2018
Posts: 2943
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| Posted: Tue Apr 22, 2025 1:08 pm Post subject: Re: float not precised |
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| Marcofras wrote: | | Code: |
#include <cstdio>
#include <iostream>
#include <fstream>
#include "colr.hpp"
using namespace std;
int main() {
float di = 200 / 31;
cout << di << endl;
return 0;
}
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the correct result is 6.4516129, in another program i use the result is 3. |
That's because 200/31 is an expression with higher precedence than assignment and thus gets evaluated a integer division. Then the result is assigned to di.
If you're going to write in C you need to study the order of precedence of operations. In all languages but more so in those with weak types system.
Best Regards,
Georgi |
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grknight
Retired Dev
Joined: 20 Feb 2015
Posts: 2120
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| Posted: Tue Apr 22, 2025 1:13 pm Post subject: |
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| Marcofras wrote: | now its 6.45161 that is not precised but i can be satisfied.
now i have problem with
| Code: |
if (g == 0) {r1 = 0;} else {r1 = (g * 100) / r;}
if (b == 0) {r2 = 0;} else {r2 = (b * 100) / g;}
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how use the member .f in this expression? |
What are g and r defined as?
"200.f" is a literal expression not a member reference. "200." make a literal 200 into floating-point but defaults to double. Adding "f" after that makes the literal a float. |
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Marcofras
n00b
Joined: 29 May 2023
Posts: 52
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| Posted: Tue Apr 22, 2025 1:23 pm Post subject: |
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| g and r are unsigned int |
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GDH-gentoo
Veteran
Joined: 20 Jul 2019
Posts: 1860
Location: South America
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| Posted: Tue Apr 22, 2025 1:57 pm Post subject: |
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| Marcofras wrote: | | g and r are unsigned int |
Presumably you mean all of b, g, r1 and r2 are unsigned int, right? And the problem with the two if statements is...?
(Not commenting on the original post since apparently doesn't describe the actual problem)
_________________
| NeddySeagoon wrote: | I'm not a witch, I'm a retired electronics engineer  |
| Ionen wrote: | | As a packager I just don't want things to get messier with weird build systems and multiple toolchains requirements though |
Last edited by GDH-gentoo on Tue Apr 22, 2025 2:00 pm; edited 1 time in total |
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Marcofras
n00b
Joined: 29 May 2023
Posts: 52
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| Posted: Tue Apr 22, 2025 2:00 pm Post subject: |
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solved there wasnt problem i was bad data reading.
thanks and bye |
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