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Denormalized floats
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19
src/main.rs
19
src/main.rs
@ -41,8 +41,7 @@ fn interpret_single(float: u32) -> f32 {
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if characteristic == 0 {
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if mantissa != 0 {
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eprintln!("can't process denormalized floats (yet)");
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return 0.0;
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// denormalized value, handled below
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} else {
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return sign * 0.0;
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}
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@ -54,24 +53,30 @@ fn interpret_single(float: u32) -> f32 {
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}
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}
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let mut power = 2.0f32.powi(characteristic as i32 - 127);
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let mut value = sign * power;
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let mut power = if characteristic != 0 { 2.0f32.powi(characteristic as i32 - 127) } else { 2.0f32.powi(-126) };
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let mut value = if characteristic != 0 { power } else { 0.0 };
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for idx in 0..23 {
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let digit = (mantissa >> (22 - idx)) & 1;
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power /= 2.0;
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if digit == 1 {
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value += sign * power;
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value += power;
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}
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}
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value
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value.copysign(sign)
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}
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#[test]
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fn interpret_single_test() {
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let tests = [
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(0b1100_0000_1110_1000_0000_0000_0000_0000, -7.25),
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(0b1011_1111_0101_0000_0000_0000_0000_0000, -0.8125)
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(0b1011_1111_0101_0000_0000_0000_0000_0000, -0.8125),
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// denormalized float
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(0b0000_0000_0100_0000_0000_0000_0000_0000, 0.000000000000000000000000000000000000005877472),
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];
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// some sanity checks around subnormals
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assert_eq!(2.0f32.powi(-127), tests[2].1);
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assert_ne!(tests[2].1 / 2.0, 0.0);
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assert_eq!(2.0f32.powi(-127) / 2.0, tests[2].1 / 2.0);
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for test in &tests {
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assert_eq!(interpret_single(test.0), test.1);
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}
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