Manipulators

README.md

@@ -13,11 +13,12 @@ Currently supported features:
    - Create generators from `std::` containers with a single type argument, with and without indexing.
    - Create generators from `std::` containers with two type arguments.
    - Create generators from incrementable types (using `operator++(void)`).
-
-Planned/In progress features:
  - Commonly used manipulators:
    - Lazy `map`ping over generators.
    - Lazy `zip`ping of generators.
+   - Lazy `filter`ing of generators.
+
+Planned/In progress features:
  - Commonly used aggregators:
    - Lazy `fold`ing of generators.
    - Lazy `sum`ming of generators.

inc/fpgen.hpp

@@ -2,6 +2,7 @@
 #define _FPGEN_MAIN
 
 #include "generator.hpp"
+#include "manipulators.hpp"
 #include "sources.hpp"
 
 #endif

inc/manipulators.hpp

@@ -0,0 +1,80 @@
+#ifndef _FPGEN_MANIP
+#define _FPGEN_MANIP
+
+#include "generator.hpp"
+#include <array>
+#include <type_traits>
+
+/**
+ *  \brief The namespace containing all of fpgen's code.
+ */
+namespace fpgen {
+/**
+ *  \brief Maps a function over a generator.
+ *
+ *  Creates a new generator whose values are the transformed values generated by
+ * applying the given mapping function on each value in the original generator.
+ * Using the provided generator after calling fpgen::map is undefined behaviour.
+ *
+ *  \tparam TIn The type contained in the provided generator.
+ *  \tparam Fun The function signature of the mapping function.
+ *  \param[in,out] gen The generator to map over. Will be in unusable state
+ * afterwards.
+ *  \param[in] func The function to map with.
+ *  \returns A new generator whose contained type is the return type of the
+ * mapping function.
+ */
+template <typename TIn, typename Fun>
+auto map(generator<TIn> &gen, Fun func)
+    -> generator<typename std::invoke_result<Fun, TIn>::type> {
+  while (gen) {
+    co_yield func(gen());
+  }
+}
+
+/**
+ *  \brief Combines two generators into a single generator.
+ *
+ *  The result is a tuple of values, one taken from each generator. Once one of
+ * the generators runs out of values, the newly generator stops as well. Using
+ * either generator after calling this function is undefined behaviour.
+ *
+ *  \tparam T1 The type contained in the first generator.
+ *  \tparam T2 The type contained in the second generator.
+ *  \param[in, out] gen1 The first generator to use.
+ *  \param[in, out] gen2 The second generator to use.
+ *  \returns A new generator containing tuples of values from both generators.
+ */
+template <typename T1, typename T2>
+generator<std::tuple<T1, T2>> zip(generator<T1> &gen1, generator<T2> &gen2) {
+  while (gen1 && gen2) {
+    co_yield {gen1(), gen2()};
+  }
+}
+
+/**
+ *  \brief Filters a generator, keeping only values matching a predicate.
+ *
+ *  The result is a generator with as much or possibly fewer elements. Each
+ * element is an element in the original generator. Elements not matching the
+ * predicate are removed.
+ *
+ *  \tparam T The type contained in the generator.
+ *  \tparam Pred The function type of the predicate function. Should return a
+ * bool.
+ *  \param gen The generator containing the original values.
+ *  \param p The predicate.
+ *  \returns A new generator which yields all values in the original generator
+ * except those not matching the predicate.
+ */
+template <typename T, typename Pred>
+generator<T> filter(generator<T> &gen, Pred p) {
+  while (gen) {
+    T val(gen());
+    if (p(val))
+      co_yield val;
+  }
+}
+} // namespace fpgen
+
+#endif

test/Makefile

@@ -1,6 +1,6 @@
 SOURCES=$(shell find $(SRCD) -name '*.cpp')
 DEPS=$(SOURCES:$(SRCD)/%.cpp=$(OBJD)/%.d)
-TESTS=generator sources
+TESTS=generator sources manip
 TESTOBJ=$(TESTS:%=$(OBJD)/test_%.o)
 
 CONAN_PKG_OVERRIDE=gtest

test/src/test_manip.cpp

@@ -0,0 +1,135 @@
+#include "generator.hpp"
+#include "manipulators.hpp"
+#include "sources.hpp"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+#include <map>
+#include <set>
+#include <string>
+#include <vector>
+
+fpgen::generator<size_t> manip_empty() { co_return 0; }
+
+fpgen::generator<size_t> manip() {
+  size_t i = 1;
+  while (i < 1024) {
+    co_yield i;
+    i *= 2;
+  }
+  co_return i;
+}
+
+fpgen::generator<size_t> until12() {
+  for (int i = 0; i < 12; i++) {
+    co_yield i;
+  }
+  co_return 12;
+}
+
+size_t mapper(size_t v) { return v * v; }
+bool is_even(size_t v) { return (v % 2 == 0); }
+bool over_100(size_t v) { return (v > 100); }
+
+TEST(manipulators, map_empty) {
+  auto gen = manip_empty();
+  gen();
+
+  for (auto v : fpgen::map(gen, mapper)) {
+    FAIL() << "Should not return a value";
+  }
+  SUCCEED();
+}
+
+TEST(manipulators, map) {
+  auto gen = manip();
+  size_t i = 1;
+  for (auto v : fpgen::map(gen, mapper)) {
+    EXPECT_EQ(i * i, v);
+    EXPECT_TRUE(i <= 1024);
+    i *= 2;
+  }
+}
+
+TEST(manipulators, zip_both_empty) {
+  auto gen = manip_empty();
+  auto gen2 = manip_empty();
+  gen();
+  gen2();
+
+  for (auto v : fpgen::zip(gen, gen2)) {
+    FAIL() << "Should not return a value";
+  }
+  SUCCEED();
+}
+
+TEST(manipulators, zip_first_empty) {
+  auto gen = manip_empty();
+  auto gen2 = fpgen::inc((size_t)0);
+  gen();
+
+  for (auto v : fpgen::zip(gen, gen2)) {
+    FAIL() << "Should not return a value";
+  }
+  SUCCEED();
+}
+
+TEST(manipulators, zip_second_empty) {
+  auto gen = fpgen::inc((size_t)0);
+  auto gen2 = manip_empty();
+  gen2();
+
+  for (auto v : fpgen::zip(gen, gen2)) {
+    FAIL() << "Should not return a value";
+  }
+  SUCCEED();
+}
+
+TEST(manipulators, zip_none_empty) {
+  auto gen = fpgen::inc((size_t)0);
+  auto gen2 = manip();
+
+  size_t i = 0;
+  size_t j = 1;
+
+  for (auto v : fpgen::zip(gen, gen2)) {
+    EXPECT_EQ(std::get<0>(v), i);
+    EXPECT_EQ(std::get<1>(v), j);
+    EXPECT_TRUE(j <= 1024);
+    EXPECT_TRUE(i <= 10);
+
+    i++;
+    j *= 2;
+  }
+}
+
+TEST(manipulators, filter_empty) {
+  auto gen = manip_empty();
+  gen();
+
+  size_t i = 0;
+
+  for (auto v : fpgen::filter(gen, is_even)) {
+    FAIL();
+  }
+  SUCCEED();
+}
+
+TEST(manipulators, filter_to_empty) {
+  auto gen = until12();
+
+  for (auto v : fpgen::filter(gen, over_100)) {
+    FAIL();
+  }
+  SUCCEED();
+}
+
+TEST(manipulators, filter_normal) {
+  auto gen = until12();
+  size_t i = 0;
+  for (auto v : fpgen::filter(gen, is_even)) {
+    EXPECT_EQ(v, i);
+    EXPECT_TRUE(i <= 12);
+    i += 2;
+  }
+}