Merge pull request #92 from saxbophone/josh/90-from-float-leading-zero

Bugfix: leading zero error when creating Nat from float

Author: saxbophone

CMakeLists.txt

@@ -1,6 +1,6 @@
 # begin basic metadata
-# minimum CMake version required for C++20 support, among other things
-cmake_minimum_required(VERSION 3.15)
+# minimum CMake version required for C++20 support and precompiled headers
+cmake_minimum_required(VERSION 3.16)
 
 # detect if Arby is being used as a sub-project of another CMake project
 if(NOT DEFINED PROJECT_NAME)

arby/include/arby/Nat.hpp

@@ -198,7 +198,7 @@ namespace com::saxbophone::arby {
                 throw std::domain_error("Nat cannot be Infinite or NaN");
             }
             Nat output;
-            while (value > 0) {
+            while (value > 1) { // value < 1 is zero which we store implicitly as empty array
                 StorageType digit = (StorageType)std::fmod(value, Nat::BASE);
                 output._digits.push_front(digit);
                 value /= Nat::BASE;

tests/CMakeLists.txt

@@ -26,6 +26,7 @@ target_link_libraries(
         arby
         Catch2::Catch2  # unit testing framework
 )
+target_precompile_headers(tests PRIVATE <arby/Nat.hpp>)
 
 enable_testing()
 

tests/casting.cpp

@@ -56,6 +56,17 @@ TEST_CASE("arby::Nat::from_float() with non-finite value throws std::domain_erro
     }
 }
 
+TEST_CASE("arby::Nat::from_float() with value between 0 and 1") {
+    // NOTE: top range is the last float value > 1
+    long double zero_ish = GENERATE(take(1000, random(0.0L, std::nextafter(1.0L, 0.0L))));
+    CAPTURE(zero_ish);
+
+    arby::Nat object = arby::Nat::from_float(zero_ish);
+
+    // value should be correct
+    CHECK((long double)object == Approx(std::trunc(zero_ish)));
+}
+
 TEST_CASE("arby::Nat::from_float() with positive value") {
     auto power = GENERATE(0.125, 0.25, 0.5, 1, 2, 4, 8);
     auto value = GENERATE_COPY(
@@ -66,6 +77,7 @@ TEST_CASE("arby::Nat::from_float() with positive value") {
             )
         )
     );
+    CAPTURE(power, value);
 
     arby::Nat object = arby::Nat::from_float(value);