adding Fn2#curry

jnape · jnape · commit c78ed71aa93f · 2019-08-23T10:54:40.000-05:00
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -25,6 +25,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/).
 - `IO#memoize`, for memoizing an `IO` by caching its first successful result
 - `MonadError`, monads that can be thrown to and caught from
 - `Tuple2-8#fromIterable`, for populating a `TupleN` with the first `N` elements of an `Iterable`
+- `Fn2#curry`, for converting an `Fn1<Tuple2<A,B>,C>` to an `Fn2<A,B,C>`
 
 ## [4.0.0] - 2019-05-20
 ### Changed
diff --git a/src/main/java/com/jnape/palatable/lambda/functions/Fn2.java b/src/main/java/com/jnape/palatable/lambda/functions/Fn2.java
@@ -1,11 +1,13 @@
 package com.jnape.palatable.lambda.functions;
 
+import com.jnape.palatable.lambda.adt.hlist.Tuple2;
 import com.jnape.palatable.lambda.adt.product.Product2;
 import com.jnape.palatable.lambda.functor.Applicative;
 import com.jnape.palatable.lambda.internal.Runtime;
 
 import java.util.function.BiFunction;
 
+import static com.jnape.palatable.lambda.adt.hlist.HList.tuple;
 import static com.jnape.palatable.lambda.functions.Fn3.fn3;
 import static com.jnape.palatable.lambda.functions.builtin.fn1.Constantly.constantly;
 
@@ -153,6 +155,19 @@ static <A, B, C> Fn2<A, B, C> curried(Fn1<A, Fn1<B, C>> curriedFn1) {
         return (a, b) -> curriedFn1.apply(a).apply(b);
     }
 
+    /**
+     * Static factory method for wrapping an uncurried {@link Fn1} in an {@link Fn2}.
+     *
+     * @param uncurriedFn1 the uncurried {@link Fn1} to adapt
+     * @param <A>          the first input argument type
+     * @param <B>          the second input argument type
+     * @param <C>          the output type
+     * @return the {@link Fn2}
+     */
+    static <A, B, C> Fn2<A, B, C> curry(Fn1<? super Tuple2<A, B>, ? extends C> uncurriedFn1) {
+        return (a, b) -> uncurriedFn1.apply(tuple(a, b));
+    }
+
     /**
      * Static method to aid inference.
      *
diff --git a/src/test/java/com/jnape/palatable/lambda/functions/Fn2Test.java b/src/test/java/com/jnape/palatable/lambda/functions/Fn2Test.java
@@ -2,9 +2,11 @@
 
 import org.junit.Test;
 
+import java.util.Map;
 import java.util.function.BiFunction;
 
 import static com.jnape.palatable.lambda.adt.hlist.HList.tuple;
+import static com.jnape.palatable.lambda.functions.builtin.fn2.Into.into;
 import static org.hamcrest.core.Is.is;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThat;
@@ -52,4 +54,10 @@ public void fromBiFunction() {
         BiFunction<String, String, String> biFunction = String::format;
         assertEquals("foo bar", Fn2.fromBiFunction(biFunction).apply("foo %s", "bar"));
     }
+
+    @Test
+    public void curry() {
+        Fn1<Map.Entry<String, String>, String> uncurried = into((a, b) -> a + b);
+        assertEquals("foobar", Fn2.curry(uncurried).apply("foo", "bar"));
+    }
 }
