Adding Show typeclass

arrow-typeclasses/src/main/kotlin/arrow/typeclasses/Show.kt

@@ -0,0 +1,55 @@
+package arrow.typeclasses
+
+import arrow.*
+
+
+/**
+ * A type class used to get a textual representation for an instance of type [F] in a type safe way.
+ *
+ */
+@typeclass
+interface Show<in F> : TC {
+
+    /**
+     * Given an object [a] of type [F] it returns its textual representation.
+     *
+     * @param a object of type [F].
+     * @returns a [String] representing [a].
+     */
+    fun show(a: F): String
+
+    companion object {
+
+        /**
+         * Construct a [Show] instance from a function `(F) -> String`
+         *
+         * @param fshow function that defines a textual representation for type [F].
+         * @returns a [Show] instance that is defined by the [fshow] function.
+         */
+        operator inline fun <F> invoke(crossinline fshow: (F) -> String): Show<F> = object : Show<F> {
+            override fun show(a: F): String =
+                    fshow(a)
+        }
+
+        /**
+         * Construct a [Show] instance using object `toString`.
+         *
+         * @param a object of type [F].
+         * @returns a [Show] instance that is defined by the [F] `toString` method.
+         */
+        fun <F> fromToString(a: F): Show<F> = object : Show<F> {
+            override fun show(a: F): String =
+                    a.toString()
+        }
+
+        /**
+         * Retrieve a [Show] that defines the textual representation as toString() for type [F].
+         */
+        fun any(): Show<Any?> = ShowAny
+
+        private object ShowAny : Show<Any?> {
+            override fun show(a: Any?): String =
+                    a.toString()
+        }
+    }
+}