Added drop_while/take_while

Author: jay-tux

README.md

@@ -1,6 +1,6 @@
 # fpgen
 *Functional programming in C++ using C++20 coroutines*  
-![](https://img.shields.io/badge/test_coverage-98%25-brightgreen)
+![](https://img.shields.io/badge/test_coverage-97%25-brightgreen)
 
 
 ## Aim

inc/manipulators.hpp

@@ -96,6 +96,34 @@ template <typename T> generator<T> take(generator<T> gen, size_t count) {
   }
   co_return;
 }
+
+template <typename T, typename Pred>
+generator<T> drop_while(generator<T> gen, Pred p) {
+  while (gen) {
+    T temp = gen();
+    if (!p(temp)) {
+      co_yield temp;
+      break;
+    }
+  }
+
+  while (gen) {
+    co_yield gen();
+  }
+  co_return;
+}
+
+template <typename T, typename Pred>
+generator<T> take_while(generator<T> gen, Pred p) {
+  while (gen) {
+    T val = gen();
+    if (!p(val)) {
+      break;
+    }
+    co_yield val;
+  }
+  co_return;
+}
 } // namespace fpgen
 
 #endif

test/src/test_manip.cpp

@@ -184,3 +184,41 @@ TEST(manipulators, drop_take) {
   }
   SUCCEED();
 }
+
+TEST(manipulators, drop_while_empty) {
+  auto gen = drop_while(manip_empty(), [](size_t v) { return v > 3; });
+  for (auto v : gen) {
+    FAIL() << "should not return a value";
+  }
+  SUCCEED();
+}
+
+TEST(manipulators, drop_while_normal) {
+  auto gen = drop_while(until12(), [](size_t v) { return v < 5; });
+  size_t exp = 5;
+  for (auto v : gen) {
+    EXPECT_EQ(v, exp);
+    EXPECT_TRUE(exp <= 12);
+    exp++;
+  }
+  EXPECT_EQ(exp, 13);
+}
+
+TEST(manipulators, take_while_empty) {
+  auto gen = take_while(manip_empty(), [](size_t v) { return v < 4; });
+  for (auto v : gen) {
+    FAIL() << "should not return a value";
+  }
+  SUCCEED();
+}
+
+TEST(manipulators, take_while_normal) {
+  auto gen = take_while(fpgen::inc((size_t)0), [](size_t v) { return v < 8; });
+  size_t exp = 0;
+  for (auto v : gen) {
+    EXPECT_EQ(v, exp);
+    EXPECT_TRUE(exp <= 8);
+    exp++;
+  }
+  EXPECT_EQ(exp, 8);
+}