Improve fmt float

* Move to a separate float mod
* Add more tests for f64 f32 lower exp upper exp
* Use assert_eq for a clearer error message

src/libcore/fmt/float.rs

@@ -0,0 +1,94 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use fmt::{Formatter, Result, LowerExp, UpperExp, Display, Debug};
+use num::flt2dec;
+
+// Common code of floating point Debug and Display.
+fn float_to_decimal_common<T>(fmt: &mut Formatter, num: &T, negative_zero: bool) -> Result
+    where T: flt2dec::DecodableFloat
+{
+    let force_sign = fmt.sign_plus();
+    let sign = match (force_sign, negative_zero) {
+        (false, false) => flt2dec::Sign::Minus,
+        (false, true)  => flt2dec::Sign::MinusRaw,
+        (true,  false) => flt2dec::Sign::MinusPlus,
+        (true,  true)  => flt2dec::Sign::MinusPlusRaw,
+    };
+
+    let mut buf = [0; 1024]; // enough for f32 and f64
+    let mut parts = [flt2dec::Part::Zero(0); 16];
+    let formatted = if let Some(precision) = fmt.precision {
+        flt2dec::to_exact_fixed_str(flt2dec::strategy::grisu::format_exact, *num, sign,
+                                    precision, false, &mut buf, &mut parts)
+    } else {
+        flt2dec::to_shortest_str(flt2dec::strategy::grisu::format_shortest, *num, sign,
+                                 0, false, &mut buf, &mut parts)
+    };
+    fmt.pad_formatted_parts(&formatted)
+}
+
+// Common code of floating point LowerExp and UpperExp.
+fn float_to_exponential_common<T>(fmt: &mut Formatter, num: &T, upper: bool) -> Result
+    where T: flt2dec::DecodableFloat
+{
+    let force_sign = fmt.sign_plus();
+    let sign = match force_sign {
+        false => flt2dec::Sign::Minus,
+        true  => flt2dec::Sign::MinusPlus,
+    };
+
+    let mut buf = [0; 1024]; // enough for f32 and f64
+    let mut parts = [flt2dec::Part::Zero(0); 16];
+    let formatted = if let Some(precision) = fmt.precision {
+        // 1 integral digit + `precision` fractional digits = `precision + 1` total digits
+        flt2dec::to_exact_exp_str(flt2dec::strategy::grisu::format_exact, *num, sign,
+                                  precision + 1, upper, &mut buf, &mut parts)
+    } else {
+        flt2dec::to_shortest_exp_str(flt2dec::strategy::grisu::format_shortest, *num, sign,
+                                     (0, 0), upper, &mut buf, &mut parts)
+    };
+    fmt.pad_formatted_parts(&formatted)
+}
+
+macro_rules! floating {
+    ($ty:ident) => (
+        #[stable(feature = "rust1", since = "1.0.0")]
+        impl Debug for $ty {
+            fn fmt(&self, fmt: &mut Formatter) -> Result {
+                float_to_decimal_common(fmt, self, true)
+            }
+        }
+
+        #[stable(feature = "rust1", since = "1.0.0")]
+        impl Display for $ty {
+            fn fmt(&self, fmt: &mut Formatter) -> Result {
+                float_to_decimal_common(fmt, self, false)
+            }
+        }
+
+        #[stable(feature = "rust1", since = "1.0.0")]
+        impl LowerExp for $ty {
+            fn fmt(&self, fmt: &mut Formatter) -> Result {
+                float_to_exponential_common(fmt, self, false)
+            }
+        }
+
+        #[stable(feature = "rust1", since = "1.0.0")]
+        impl UpperExp for $ty {
+            fn fmt(&self, fmt: &mut Formatter) -> Result {
+                float_to_exponential_common(fmt, self, true)
+            }
+        }
+    )
+}
+
+floating! { f32 }
+floating! { f64 }

src/libcore/fmt/mod.rs

@@ -21,6 +21,10 @@ use result;
 use slice;
 use str;
 
+mod float;
+mod num;
+mod builders;
+
 #[unstable(feature = "fmt_flags_align", issue = "27726")]
 /// Possible alignments returned by `Formatter::align`
 #[derive(Debug)]
@@ -38,9 +42,6 @@ pub enum Alignment {
 #[stable(feature = "debug_builders", since = "1.2.0")]
 pub use self::builders::{DebugStruct, DebugTuple, DebugSet, DebugList, DebugMap};
 
-mod num;
-mod builders;
-
 #[unstable(feature = "fmt_internals", reason = "internal to format_args!",
            issue = "0")]
 #[doc(hidden)]
@@ -1511,86 +1512,6 @@ impl<'a, T: ?Sized> Pointer for &'a mut T {
     }
 }
 
-// Common code of floating point Debug and Display.
-fn float_to_decimal_common<T>(fmt: &mut Formatter, num: &T, negative_zero: bool) -> Result
-    where T: flt2dec::DecodableFloat
-{
-    let force_sign = fmt.sign_plus();
-    let sign = match (force_sign, negative_zero) {
-        (false, false) => flt2dec::Sign::Minus,
-        (false, true)  => flt2dec::Sign::MinusRaw,
-        (true,  false) => flt2dec::Sign::MinusPlus,
-        (true,  true)  => flt2dec::Sign::MinusPlusRaw,
-    };
-
-    let mut buf = [0; 1024]; // enough for f32 and f64
-    let mut parts = [flt2dec::Part::Zero(0); 16];
-    let formatted = if let Some(precision) = fmt.precision {
-        flt2dec::to_exact_fixed_str(flt2dec::strategy::grisu::format_exact, *num, sign,
-                                    precision, false, &mut buf, &mut parts)
-    } else {
-        flt2dec::to_shortest_str(flt2dec::strategy::grisu::format_shortest, *num, sign,
-                                 0, false, &mut buf, &mut parts)
-    };
-    fmt.pad_formatted_parts(&formatted)
-}
-
-// Common code of floating point LowerExp and UpperExp.
-fn float_to_exponential_common<T>(fmt: &mut Formatter, num: &T, upper: bool) -> Result
-    where T: flt2dec::DecodableFloat
-{
-    let force_sign = fmt.sign_plus();
-    let sign = match force_sign {
-        false => flt2dec::Sign::Minus,
-        true  => flt2dec::Sign::MinusPlus,
-    };
-
-    let mut buf = [0; 1024]; // enough for f32 and f64
-    let mut parts = [flt2dec::Part::Zero(0); 16];
-    let formatted = if let Some(precision) = fmt.precision {
-        // 1 integral digit + `precision` fractional digits = `precision + 1` total digits
-        flt2dec::to_exact_exp_str(flt2dec::strategy::grisu::format_exact, *num, sign,
-                                  precision + 1, upper, &mut buf, &mut parts)
-    } else {
-        flt2dec::to_shortest_exp_str(flt2dec::strategy::grisu::format_shortest, *num, sign,
-                                     (0, 0), upper, &mut buf, &mut parts)
-    };
-    fmt.pad_formatted_parts(&formatted)
-}
-
-macro_rules! floating { ($ty:ident) => {
-
-    #[stable(feature = "rust1", since = "1.0.0")]
-    impl Debug for $ty {
-        fn fmt(&self, fmt: &mut Formatter) -> Result {
-            float_to_decimal_common(fmt, self, true)
-        }
-    }
-
-    #[stable(feature = "rust1", since = "1.0.0")]
-    impl Display for $ty {
-        fn fmt(&self, fmt: &mut Formatter) -> Result {
-            float_to_decimal_common(fmt, self, false)
-        }
-    }
-
-    #[stable(feature = "rust1", since = "1.0.0")]
-    impl LowerExp for $ty {
-        fn fmt(&self, fmt: &mut Formatter) -> Result {
-            float_to_exponential_common(fmt, self, false)
-        }
-    }
-
-    #[stable(feature = "rust1", since = "1.0.0")]
-    impl UpperExp for $ty {
-        fn fmt(&self, fmt: &mut Formatter) -> Result {
-            float_to_exponential_common(fmt, self, true)
-        }
-    }
-} }
-floating! { f32 }
-floating! { f64 }
-
 // Implementation of Display/Debug for various core types
 
 #[stable(feature = "rust1", since = "1.0.0")]

src/libcoretest/fmt/float.rs

@@ -9,11 +9,29 @@
 // except according to those terms.
 
 #[test]
-fn test_format_float() {
-    assert!("1" == format!("{:.0}", 1.0f64));
-    assert!("9" == format!("{:.0}", 9.4f64));
-    assert!("10" == format!("{:.0}", 9.9f64));
-    assert!("9.8" == format!("{:.1}", 9.849f64));
-    assert!("9.9" == format!("{:.1}", 9.851f64));
-    assert!("1" == format!("{:.0}", 0.5f64));
+fn test_format_f64() {
+    assert_eq!("1", format!("{:.0}", 1.0f64));
+    assert_eq!("9", format!("{:.0}", 9.4f64));
+    assert_eq!("10", format!("{:.0}", 9.9f64));
+    assert_eq!("9.8", format!("{:.1}", 9.849f64));
+    assert_eq!("9.9", format!("{:.1}", 9.851f64));
+    assert_eq!("1", format!("{:.0}", 0.5f64));
+    assert_eq!("1.23456789e6", format!("{:e}", 1234567.89f64));
+    assert_eq!("1.23456789e3", format!("{:e}", 1234.56789f64));
+    assert_eq!("1.23456789E6", format!("{:E}", 1234567.89f64));
+    assert_eq!("1.23456789E3", format!("{:E}", 1234.56789f64));
+}
+
+#[test]
+fn test_format_f32() {
+    assert_eq!("1", format!("{:.0}", 1.0f32));
+    assert_eq!("9", format!("{:.0}", 9.4f32));
+    assert_eq!("10", format!("{:.0}", 9.9f32));
+    assert_eq!("9.8", format!("{:.1}", 9.849f32));
+    assert_eq!("9.9", format!("{:.1}", 9.851f32));
+    assert_eq!("1", format!("{:.0}", 0.5f32));
+    assert_eq!("1.2345679e6", format!("{:e}", 1234567.89f32));
+    assert_eq!("1.2345679e3", format!("{:e}", 1234.56789f32));
+    assert_eq!("1.2345679E6", format!("{:E}", 1234567.89f32));
+    assert_eq!("1.2345679E3", format!("{:E}", 1234.56789f32));
 }