fix(predicate): Break out boolean logic from trait

BREAKING CHANGE: `Predicate` trait is changed but most use cases should
not be impacted.

Author: epage

src/boolean.rs

@@ -132,3 +132,73 @@ where
         !self.inner.eval(item)
     }
 }
+
+/// `Predicate` extension that adds boolean logic.
+pub trait PredicateBooleanExt<Item: ?Sized>
+where
+    Self: Predicate<Item>,
+{
+    /// Compute the logical AND of two `Predicate` results, returning the result.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use predicates::prelude::*;
+    ///
+    /// let predicate_fn1 = predicate::always().and(predicate::always());
+    /// let predicate_fn2 = predicate::always().and(predicate::never());
+    /// assert_eq!(true, predicate_fn1.eval(&4));
+    /// assert_eq!(false, predicate_fn2.eval(&4));
+    fn and<B>(self, other: B) -> AndPredicate<Self, B, Item>
+    where
+        B: Predicate<Item>,
+        Self: Sized,
+    {
+        AndPredicate::new(self, other)
+    }
+
+    /// Compute the logical OR of two `Predicate` results, returning the result.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use predicates::prelude::*;
+    ///
+    /// let predicate_fn1 = predicate::always().or(predicate::always());
+    /// let predicate_fn2 = predicate::always().or(predicate::never());
+    /// let predicate_fn3 = predicate::never().or(predicate::never());
+    /// assert_eq!(true, predicate_fn1.eval(&4));
+    /// assert_eq!(true, predicate_fn2.eval(&4));
+    /// assert_eq!(false, predicate_fn3.eval(&4));
+    fn or<B>(self, other: B) -> OrPredicate<Self, B, Item>
+    where
+        B: Predicate<Item>,
+        Self: Sized,
+    {
+        OrPredicate::new(self, other)
+    }
+
+    /// Compute the logical NOT of a `Predicate`, returning the result.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use predicates::prelude::*;
+    ///
+    /// let predicate_fn1 = predicate::always().not();
+    /// let predicate_fn2 = predicate::never().not();
+    /// assert_eq!(false, predicate_fn1.eval(&4));
+    /// assert_eq!(true, predicate_fn2.eval(&4));
+    fn not(self) -> NotPredicate<Self, Item>
+    where
+        Self: Sized,
+    {
+        NotPredicate::new(self)
+    }
+}
+
+impl<P, Item> PredicateBooleanExt<Item> for P
+where
+    P: Predicate<Item>,
+{
+}

src/core.rs

@@ -6,7 +6,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use boolean::{AndPredicate, NotPredicate, OrPredicate};
 use boxed::BoxPredicate;
 
 /// Trait for generically evaluating a type against a dynamically created
@@ -21,64 +20,6 @@ pub trait Predicate<Item: ?Sized> {
     /// boolean.
     fn eval(&self, variable: &Item) -> bool;
 
-    /// Compute the logical AND of two `Predicate` results, returning the result.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use predicates::prelude::*;
-    ///
-    /// let predicate_fn1 = predicate::always().and(predicate::always());
-    /// let predicate_fn2 = predicate::always().and(predicate::never());
-    /// assert_eq!(true, predicate_fn1.eval(&4));
-    /// assert_eq!(false, predicate_fn2.eval(&4));
-    fn and<B>(self, other: B) -> AndPredicate<Self, B, Item>
-    where
-        B: Predicate<Item>,
-        Self: Sized,
-    {
-        AndPredicate::new(self, other)
-    }
-
-    /// Compute the logical OR of two `Predicate` results, returning the result.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use predicates::prelude::*;
-    ///
-    /// let predicate_fn1 = predicate::always().or(predicate::always());
-    /// let predicate_fn2 = predicate::always().or(predicate::never());
-    /// let predicate_fn3 = predicate::never().or(predicate::never());
-    /// assert_eq!(true, predicate_fn1.eval(&4));
-    /// assert_eq!(true, predicate_fn2.eval(&4));
-    /// assert_eq!(false, predicate_fn3.eval(&4));
-    fn or<B>(self, other: B) -> OrPredicate<Self, B, Item>
-    where
-        B: Predicate<Item>,
-        Self: Sized,
-    {
-        OrPredicate::new(self, other)
-    }
-
-    /// Compute the logical NOT of a `Predicate`, returning the result.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use predicates::prelude::*;
-    ///
-    /// let predicate_fn1 = predicate::always().not();
-    /// let predicate_fn2 = predicate::never().not();
-    /// assert_eq!(false, predicate_fn1.eval(&4));
-    /// assert_eq!(true, predicate_fn2.eval(&4));
-    fn not(self) -> NotPredicate<Self, Item>
-    where
-        Self: Sized,
-    {
-        NotPredicate::new(self)
-    }
-
     /// Returns a `BoxPredicate` wrapper around this `Predicate` type.
     ///
     /// Returns a `BoxPredicate` wrapper around this `Predicate type. The

src/prelude.rs

@@ -9,6 +9,7 @@
 //! Module that contains the essentials for working with predicates.
 
 pub use core::Predicate;
+pub use boolean::PredicateBooleanExt;
 
 /// Predicate factories
 pub mod predicate {