introduce Functions

platform/util-rt/src/com/intellij/openapi/util/Conditions.java

@@ -18,6 +18,7 @@ package com.intellij.openapi.util;
 
 import com.intellij.reference.SoftReference;
 import com.intellij.util.ArrayUtilRt;
+import com.intellij.util.Function;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.HashMap;
@@ -48,6 +49,15 @@ public class Conditions {
     };
   }
 
+  public static Condition<Class> assignableTo(final Class clazz) {
+    return new Condition<Class>() {
+      @Override
+      public boolean value(Class t) {
+        return clazz.isAssignableFrom(t);
+      }
+    };
+  }
+
   public static <T> Condition<T> instanceOf(final Class<?>... clazz) {
     return new Condition<T>() {
       @Override
@@ -114,6 +124,15 @@ public class Conditions {
     return new Or<T>(c1, c2);
   }
 
+  public static <A, B> Condition<A> compose(final Function<? super A, B> fun, final Condition<? super B> condition) {
+    return new Condition<A>() {
+      @Override
+      public boolean value(A o) {
+        return condition.value(fun.fun(o));
+      }
+    };
+  }
+
   public static <T> Condition<T> cached(Condition<T> c) {
     return new SoftRefCache<T>(c);
   }

platform/util-rt/src/com/intellij/util/Functions.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2000-2015 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.intellij.util;
+
+import com.intellij.openapi.util.Pair;
+
+import java.util.Map;
+
+/**
+ * @author gregsh
+ */
+public class Functions {
+
+  public static <A, B> Function<A, B> identity() {
+    return Function.ID;
+  }
+
+  public static <A> Function<A, String> toString() {
+    return Function.TO_STRING;
+  }
+
+  public static <A, B> Function<A, B> fromMap(final Map<A, B> map) {
+    return new Function<A, B>() {
+      @Override
+      public B fun(A a) {
+        return map.get(a);
+      }
+    };
+  }
+
+  private static final Function PAIR_FIRST = new Function<Pair<?, ?>, Object>() {
+    @Override
+    public Object fun(Pair<?, ?> pair) {
+      return Pair.getFirst(pair);
+    }
+  };
+
+  private static final Function PAIR_SECOND = new Function<Pair<?, ?>, Object>() {
+    @Override
+    public Object fun(Pair<?, ?> pair) {
+      return Pair.getSecond(pair);
+    }
+  };
+
+  public static <A> Function<Pair<A, ?>, A> pairFirst() {
+    //noinspection unchecked
+    return (Function<Pair<A, ?>, A>)PAIR_FIRST;
+  }
+
+  public static <B> Function<Pair<?, B>, B> pairSecond() {
+    //noinspection unchecked
+    return (Function<Pair<?, B>, B>)PAIR_SECOND;
+  }
+}