added recurse_n (flexflow#1563)

* added recurse_n

* fix

---------

Co-authored-by: Pietro Max Marsella <marsella@stanford.edu>

Author: Marsella8

lib/utils/include/utils/containers/recurse_n.h

@@ -0,0 +1,34 @@
+#ifndef _FLEXFLOW_LIB_UTILS_INCLUDE_UTILS_CONTAINERS_RECURSE_N_H
+#define _FLEXFLOW_LIB_UTILS_INCLUDE_UTILS_CONTAINERS_RECURSE_N_H
+
+#include "utils/exception.h"
+
+namespace FlexFlow {
+
+/**
+ * @brief
+ * Applies function `f` to value `initial_value` n times recursively.
+ *
+ * @example
+ *   auto add_three = [](int x) { return x + 3; };
+ *   int result = recurse_n(add_three, 3, 5);
+ *   result -> f(f(f(5))) = ((5+3)+3)+3 = 14
+ *
+ * @throws RuntimeError if n is negative
+ */
+template <typename F, typename T>
+T recurse_n(F const &f, int n, T const &initial_value) {
+  if (n < 0) {
+    throw mk_runtime_error(
+        fmt::format("Supplied n={} should be non-negative", n));
+  }
+  T t = initial_value;
+  for (int i = 0; i < n; i++) {
+    t = f(t);
+  }
+  return t;
+}
+
+} // namespace FlexFlow
+
+#endif

lib/utils/src/utils/containers/recurse_n.cc

@@ -0,0 +1,12 @@
+#include "utils/containers/recurse_n.h"
+#include "utils/archetypes/value_type.h"
+#include <functional>
+
+namespace FlexFlow {
+
+using T = value_type<0>;
+using F = std::function<T(T)>; // F :: T -> T
+
+template T recurse_n(F const &f, int n, T const &initial_value);
+
+} // namespace FlexFlow

lib/utils/test/src/utils/containers/recurse_n.cc

@@ -0,0 +1,29 @@
+#include "utils/containers/recurse_n.h"
+#include <doctest/doctest.h>
+#include <string>
+
+using namespace FlexFlow;
+
+TEST_SUITE(FF_TEST_SUITE) {
+  TEST_CASE("recurse_n") {
+    auto append_bar = [](std::string const &x) {
+      return x + std::string("Bar");
+    };
+
+    SUBCASE("n = 0") {
+      std::string result = recurse_n(append_bar, 0, std::string("Foo"));
+      std::string correct = "Foo";
+      CHECK(result == correct);
+    }
+
+    SUBCASE("n = 3") {
+      std::string result = recurse_n(append_bar, 3, std::string("Foo"));
+      std::string correct = "FooBarBarBar";
+      CHECK(result == correct);
+    }
+
+    SUBCASE("n < 0") {
+      CHECK_THROWS(recurse_n(append_bar, -1, std::string("Foo")));
+    }
+  }
+}