Break type checks into separate traits

types/src/bool.rs

@@ -3,17 +3,22 @@
  */
 
 use std::any::Any;
-use super::value::*;
+use value::*;
 
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub struct Bool(pub bool);
 
 impl Value for Bool {
     fn as_value(&self) -> &Value { self }
+}
 
+impl IsBool for Bool {
     fn is_bool(&self) -> bool { true }
 }
 
+impl IsChar for Bool { }
+impl IsNumber for Bool { }
+
 impl ValueEq for Bool {
     fn eq(&self, other: &Value) -> bool {
         other.as_any().downcast_ref::<Self>().map_or(false, |x| x == self)

types/src/char.rs

@@ -10,10 +10,15 @@ pub struct Char(pub char);
 
 impl Value for Char {
     fn as_value(&self) -> &Value { self }
+}
 
+impl IsChar for Char {
     fn is_char(&self) -> bool { true }
 }
 
+impl IsBool for Char { }
+impl IsNumber for Char { }
+
 impl ValueEq for Char {
     fn eq(&self, other: &Value) -> bool {
         other.as_any().downcast_ref::<Self>().map_or(false, |x| x == self)

types/src/value.rs

@@ -5,15 +5,33 @@
 use std::fmt::Debug;
 use std::any::Any;
 
-pub trait Value: Debug + ValueEq {
+pub trait Value: Debug + IsBool + IsChar + IsNumber + ValueEq {
     fn as_value(&self) -> &Value;
+}
 
+pub trait IsBool {
     /// Should return `true` if this Value is a Bool.
     fn is_bool(&self) -> bool { false }
+}
+
+pub trait IsChar {
     /// Should return `true` if this Value is a Char.
     fn is_char(&self) -> bool { false }
 }
 
+pub trait IsNumber {
+    /// Should return `true` if this Value is a number type.
+    fn is_number(&self) -> bool { self.is_complex() || self.is_real() || self.is_rational() || self.is_integer() }
+    /// Should return `true` if this Value is a complex number type.
+    fn is_complex(&self) -> bool { false }
+    /// Should return `true` if this Value is a real number type.
+    fn is_real(&self) -> bool { false }
+    /// Should return `true` if this Value is a rational number type.
+    fn is_rational(&self) -> bool { false }
+    /// Should return `true` if this Value is a integer number type.
+    fn is_integer(&self) -> bool { false }
+}
+
 /// A trait on value types that makes it easier to compare values of disparate types. The methods
 /// provided by this trait are used by the PartialEq implementation on Values.
 pub trait ValueEq {