40 lines
1.1 KiB
Markdown
40 lines
1.1 KiB
Markdown
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# round/floor a f32 using logical operations and integer arithmetical operations in Rust
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Yith this function you can able to truncate a float f32 using bitwise, logical operations and integer arithmetical operation.
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The function has not 100% of precisition because ignore most of the bits in the mantissa, but it's often to round small numbers.
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```Rust
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fn round(mut f: f32) -> i32 {
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let sign = f < 0.0;
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if sign {
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f = f * -1.0;
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}
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let digits = f.to_bits();
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let mut exponent = (digits as i32 >> 23) & (!(1 << 8));
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let mantissa = (digits - (digits >> 23 << 23)) >> 16 | 1 << 7;
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exponent -= 127;
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if exponent < 0 {
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return 0;
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}
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let exponent: u32 = 1 << exponent as u32;
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let mut result: i32 = (exponent * mantissa) as i32 / 128;
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if sign {
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result *= -1;
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}
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result
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}
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fn main() {
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println!("{}", round(15.125));
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println!("{}", round(14.345));
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println!("{}", round(-1.555));
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println!("{}", round(-9.001));
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println!("{}", round(-999.001));
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println!("{}", round(-0.5));
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}
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```
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