Add Float::Primitive#sign_bit

spec/manual/string_to_f32_spec.cr

@@ -19,7 +19,7 @@ describe "x.to_s.to_f32 == x" do
           val.nan?.should be_true
         else
           val.should eq(float)
-          Math.copysign(1, val).should eq(Math.copysign(1, float))
+          val.sign_bit.should eq(float.sign_bit)
         end
       end
     end

spec/std/complex_spec.cr

@@ -8,8 +8,8 @@ require "../support/number"
 # exact equality, including component signs
 private def assert_complex_eq(z1 : Complex, z2 : Complex, *, file = __FILE__, line = __LINE__)
   z1.should eq(z2), file: file, line: line
-  Math.copysign(1.0, z1.real).should eq(Math.copysign(1.0, z2.real)), file: file, line: line
-  Math.copysign(1.0, z1.imag).should eq(Math.copysign(1.0, z2.imag)), file: file, line: line
+  z1.real.sign_bit.should eq(z2.real.sign_bit), file: file, line: line
+  z1.imag.sign_bit.should eq(z2.imag.sign_bit), file: file, line: line
 end
 
 private def assert_complex_nan(z : Complex, *, file = __FILE__, line = __LINE__)

spec/std/float_spec.cr

@@ -442,14 +442,14 @@ describe "Float" do
   end
 
   it "#abs" do
-    Math.copysign(1_f64, 0.0_f64.abs).should eq 1_f64
-    Math.copysign(1_f64, -0.0_f64.abs).should eq 1_f64
+    0.0_f64.abs.sign_bit.should eq 1
+    -0.0_f64.abs.sign_bit.should eq 1
 
     0.1_f64.abs.should eq 0.1_f64
     -0.1_f64.abs.should eq 0.1_f64
 
-    Math.copysign(1_f32, 0.0_f32.abs).should eq 1_f32
-    Math.copysign(1_f32, -0.0_f32.abs).should eq 1_f32
+    0.0_f32.abs.sign_bit.should eq 1_f32
+    -0.0_f32.abs.sign_bit.should eq 1_f32
 
     0.1_f32.abs.should eq 0.1_f32
     -0.1_f32.abs.should eq 0.1_f32
@@ -464,4 +464,24 @@ describe "Float" do
     Float32::INFINITY.abs.should eq Float32::INFINITY
     (-Float32::INFINITY).abs.should eq Float32::INFINITY
   end
+
+  it "#sign_bit" do
+    1.2_f64.sign_bit.should eq(1)
+    -1.2_f64.sign_bit.should eq(-1)
+    0.0_f64.sign_bit.should eq(1)
+    -0.0_f64.sign_bit.should eq(-1)
+    Float64::INFINITY.sign_bit.should eq(1)
+    (-Float64::INFINITY).sign_bit.should eq(-1)
+    0x7ff0_0000_0000_0001_u64.unsafe_as(Float64).sign_bit.should eq(1)
+    0xfff0_0000_0000_0001_u64.unsafe_as(Float64).sign_bit.should eq(-1)
+
+    1.2_f32.sign_bit.should eq(1)
+    -1.2_f32.sign_bit.should eq(-1)
+    0.0_f32.sign_bit.should eq(1)
+    -0.0_f32.sign_bit.should eq(-1)
+    Float32::INFINITY.sign_bit.should eq(1)
+    (-Float32::INFINITY).sign_bit.should eq(-1)
+    0x7f80_0001_u32.unsafe_as(Float32).sign_bit.should eq(1)
+    0xff80_0001_u32.unsafe_as(Float32).sign_bit.should eq(-1)
+  end
 end

src/complex.cr

@@ -82,7 +82,7 @@ struct Complex
   # ```
   def to_s(io : IO) : Nil
     io << @real
-    io << (@imag.nan? || Math.copysign(1.0, @imag) > 0 ? " + " : " - ")
+    io << (@imag.nan? || @imag.sign_bit > 0 ? " + " : " - ")
     io << Math.copysign(@imag, 1.0)
     io << 'i'
   end

src/float.cr

@@ -198,6 +198,13 @@ struct Float32
     Math.copysign(self, 1)
   end
 
+  # Returns `-1` if the sign bit of this float is set, `1` otherwise.
+  #
+  # Unlike `#sign`, this works on signed zeros and not-a-numbers as well.
+  def sign_bit : Int32
+    Math.copysign(1_f32, self).to_i
+  end
+
   # Rounds towards positive infinity.
   def ceil : Float32
     LibM.ceil_f32(self)
@@ -390,6 +397,13 @@ struct Float64
     Math.copysign(self, 1)
   end
 
+  # Returns `-1` if the sign bit of this float is set, `1` otherwise.
+  #
+  # Unlike `#sign`, this works on signed zeros and not-a-numbers as well.
+  def sign_bit : Int32
+    Math.copysign(1_f64, self).to_i
+  end
+
   def ceil : Float64
     LibM.ceil_f64(self)
   end

src/humanize.cr

@@ -56,7 +56,7 @@ struct Number
       integer, _, decimals = string.partition('.')
     end
 
-    is_negative = number.is_a?(Float::Primitive) ? Math.copysign(1, number) < 0 : number < 0
+    is_negative = number.responds_to?(:sign_bit) ? number.sign_bit < 0 : number < 0
 
     format_impl(io, is_negative, integer, decimals, separator, delimiter, decimal_places, group, only_significant)
   end

src/string/formatter.cr

@@ -391,7 +391,7 @@ struct String::Formatter(A)
       printf_size = Float::Printer::RyuPrintf.d2fixed_buffered_n(float, printf_precision, printf_buf.to_unsafe)
       printf_slice = printf_buf.to_slice[0, printf_size]
       dot_index = printf_slice.index('.'.ord)
-      sign = Math.copysign(1.0, float)
+      sign = float.sign_bit
 
       str_size = printf_size + trailing_zeros
       str_size += 1 if sign < 0 || flags.plus || flags.space
@@ -431,7 +431,7 @@ struct String::Formatter(A)
       printf_slice = printf_buf.to_slice[0, printf_size]
       dot_index = printf_slice.index('.'.ord)
       e_index = printf_slice.rindex!('e'.ord)
-      sign = Math.copysign(1.0, float)
+      sign = float.sign_bit
 
       printf_slice[e_index] = 'E'.ord.to_u8! if flags.uppercase?
 
@@ -469,7 +469,7 @@ struct String::Formatter(A)
       printf_slice = printf_buf.to_slice[0, printf_size]
       dot_index = printf_slice.index('.'.ord)
       e_index = printf_slice.rindex('e'.ord)
-      sign = Math.copysign(1.0, float)
+      sign = float.sign_bit
 
       printf_slice[e_index] = 'E'.ord.to_u8! if e_index && flags.uppercase?
 
@@ -499,7 +499,7 @@ struct String::Formatter(A)
 
     # Formats floats with `%a` or `%A`
     private def float_hex(float, flags)
-      sign = Math.copysign(1.0, float)
+      sign = float.sign_bit
       float = float.abs
 
       str_size = Float::Printer::Hexfloat(Float64, UInt64).to_s_size(float,