38 lines
760 B
Rust
38 lines
760 B
Rust
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pub trait Narrow{
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type Output;
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fn narrow(self)->Self::Output;
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}
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#[derive(Debug)]
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pub enum NarrowError{
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Overflow,
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Underflow,
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}
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pub trait TryNarrow{
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type Output;
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fn try_narrow(self)->Result<Self::Output,NarrowError>;
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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impl TryNarrow for i16{
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type Output=i8;
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fn try_narrow(self)->Result<Self::Output,NarrowError>{
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if self<i8::MIN as i16{
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return Err(NarrowError::Underflow);
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}
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if (i8::MAX as i16)<self{
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return Err(NarrowError::Overflow);
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}
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Ok(self as i8)
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}
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}
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#[test]
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fn test_i16_i8(){
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assert!(matches!(257i16.try_narrow(),Err(NarrowError::Overflow)));
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assert!(matches!(64i16.try_narrow(),Ok(64i8)));
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assert!(matches!((-257i16).try_narrow(),Err(NarrowError::Underflow)));
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}
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}
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