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Single-precision interpreter
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77
src/main.rs
77
src/main.rs
@ -1,5 +1,78 @@
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use std::error::Error;
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use std::env;
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fn main() {
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let args = env::args().collect::<Vec<_>>();
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fn main() -> Result<(), Box<dyn Error>> {
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let args = env::args().skip(1).collect::<Vec<_>>();
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for arg in args {
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let binary_value = parse(&arg.replace(' ', ""))?;
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println!("binary: {:032b}", binary_value);
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let transmuted = f32::from_bits(binary_value); // clippy was smart enough to notice the transmute to a f32
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println!("transmuted: {:?}", transmuted);
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println!("interpreted: {:?}", interpret_single(binary_value));
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}
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Ok(())
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}
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fn parse(binary_number: &str) -> Result<u32, Box<dyn Error>> {
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if binary_number.len() != 32 {
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return Err("argument not 32 bits".into());
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}
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let mut value: u32 = 0;
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for (idx, digit) in binary_number.chars().enumerate() {
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match digit {
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'0' => {},
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'1' => value += 1 << (31-idx),
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x => return Err(format!("argument contains more than 0s and 1s: {:?}", x).into())
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}
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}
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Ok(value)
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}
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#[test]
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fn parse_test() {
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assert_eq!(parse("10110000111111110101010110101010").unwrap(), 0b10110000111111110101010110101010);
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}
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fn interpret_single(float: u32) -> f32 {
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let sign = float.rotate_left(1) & 1;
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let sign = if sign == 1 { -1.0 } else { 0.0 };
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let characteristic = float.rotate_left(9) & 0b1111_1111;
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let mantissa = float & 0b1111_1111_1111_1111_1111_111;
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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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} else {
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return sign * 0.0;
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}
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} else if characteristic == 255 {
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if mantissa != 0 {
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return f32::NAN;
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} else {
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return sign * f32::INFINITY;
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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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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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}
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}
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value
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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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];
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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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}
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