[DOC] Harmonize #-@ methods

Merged: https://github.com/ruby/ruby/pull/15570

complex.c

@@ -799,9 +799,9 @@ rb_complex_imag(VALUE self)
 
 /*
  * call-seq:
- *   -complex -> new_complex
+ *   -self -> complex
  *
- * Returns the negation of +self+, which is the negation of each of its parts:
+ * Returns +self+, negated, which is the negation of each of its parts:
  *
  *   -Complex.rect(1, 2)   # => (-1-2i)
  *   -Complex.rect(-1, -2) # => (1+2i)

numeric.c

@@ -576,7 +576,7 @@ num_imaginary(VALUE num)
  *  call-seq:
  *    -self -> numeric
  *
- *  Unary Minus---Returns the receiver, negated.
+ *  Returns +self+, negated.
  */
 
 static VALUE

numeric.rb

@@ -93,9 +93,14 @@ end
 
 class Integer
   # call-seq:
-  #    -int -> integer
+  #   -self -> integer
+  #
+  # Returns +self+, negated:
+  #
+  #   -1    # => -1
+  #   -(-1) # => 1
+  #   -0    # => 0
   #
-  # Returns +self+, negated.
   def -@
     Primitive.attr! :leaf
     Primitive.cexpr! 'rb_int_uminus(self)'
@@ -373,9 +378,13 @@ class Float
   alias magnitude abs
 
   # call-seq:
-  #   -float -> float
+  #   -self -> float
   #
-  # Returns +self+, negated.
+  # Returns +self+, negated:
+  #
+  #   -3.14    # => -3.14
+  #   -(-3.14) # => 3.14
+  #   -0.0     # => -0.0
   #
   def -@
     Primitive.attr! :leaf

rational.c

@@ -609,9 +609,13 @@ nurat_denominator(VALUE self)
 
 /*
  * call-seq:
- *    -rat  ->  rational
+ *    -self -> rational
+ *
+ * Returns +self+, negated:
+ *
+ *   -(1/3r)   # => (-1/3)
+ *   -(-1/3r)  # => (1/3)
  *
- * Negates +rat+.
  */
 VALUE
 rb_rational_uminus(VALUE self)