From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sun, 4 Oct 2020 18:46:56 +0000 (+0100)
Subject: ord etc. for bigfloat
X-Git-Tag: otter-0.2.0~759
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=commitdiff_plain;h=b8dfb2ee67668ba03ad21ef53ef314d23b145a95;p=otter.git

ord etc. for bigfloat

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---

diff --git a/src/bigfloat.rs b/src/bigfloat.rs
index e1a58ee1..91a31777 100644
--- a/src/bigfloat.rs
+++ b/src/bigfloat.rs
@@ -2,7 +2,8 @@
 
 use crate::imports::*;
 
-enum Sign { Pos, Neg, }
+#[derive(Copy,Clone,Debug,Ord,Eq,PartialOrd,PartialEq)]
+enum Sign { Neg, Pos, }
 use Sign::*;
 
 type Sz = u16;
@@ -208,6 +209,41 @@ impl Debug for Bigfloat {
   }    
 }
 
+impl Ord for Bigfloat {
+  fn cmp(&self, other: &Bigfloat) -> Ordering {
+    let (ah, al) = self.as_parts();
+    let (bh, bl) = other.as_parts();
+
+    {
+
+      ah.sign.cmp(&bh.sign)
+
+    }.then_with(||{
+
+      let mut x = ah.exp.cmp(&bh.exp);
+      if ah.sign == Neg { x = x.reverse() }
+      x
+
+    }.then_with(||{
+
+      al.cmp(bl)
+
+    }))
+  }
+}
+impl PartialOrd for Bigfloat {
+  fn partial_cmp(&self, other: &Bigfloat) -> Option<Ordering> {
+    Some(self.cmp(other))
+  }
+}
+impl Eq for Bigfloat {
+}
+impl PartialEq for Bigfloat {
+  fn eq(&self, other: &Bigfloat) -> bool {
+    self.cmp(other) == Ordering::Equal
+  }
+}
+
 #[derive(Error,Clone,Copy,Debug)]
 #[error("error parsing bigfloat (z value)")]
 pub struct ParseError;
@@ -242,4 +278,19 @@ mod test {
     assert_eq!(format!("{:?}", &b2),
                format!(r#"Bf"{}""#, &b2));
   }
+
+  #[test]
+  fn equality() {
+    assert!( Bigfloat::from_str("!0000 ffff_ffff_fff0") <
+             Bigfloat::from_str("!0000 ffff_ffff_fff3") );
+    
+    assert!( Bigfloat::from_str("!0001 ffff_ffff_ffff") <
+             Bigfloat::from_str("!0000 ffff_ffff_0000") );
+    
+    assert!( Bigfloat::from_str("+0000 ffff_ffff_0000") <
+             Bigfloat::from_str("+0001 ffff_ffff_ffff") );
+    
+    assert!( Bigfloat::from_str("+0000 ffff_ffff_0000") <
+             Bigfloat::from_str("+0000 ffff_ffff_0000 1234_ffff_0000") );
+  }
 }
diff --git a/src/imports.rs b/src/imports.rs
index 9cdcaed4..f8809df7 100644
--- a/src/imports.rs
+++ b/src/imports.rs
@@ -20,7 +20,7 @@ pub use std::iter;
 pub use std::iter::repeat_with;
 pub use std::collections::VecDeque;
 pub use std::num::Wrapping;
-pub use std::cmp::{self,min,max};
+pub use std::cmp::{self,min,max,Ordering};
 pub use std::error::Error;
 pub use std::marker::PhantomData;
 pub use std::ops::{Deref,DerefMut};