mark Quantity double operator overload const

Author: SizzinSeal

Makefile

@@ -29,7 +29,7 @@ IS_LIBRARY:=1
 # Be sure that your header files are in the include directory inside of a folder with the
 # same name as what you set LIBNAME to below.
 LIBNAME:=units
-VERSION:=0.7.0
+VERSION:=0.7.1
 # EXCLUDE_SRC_FROM_LIB= $(SRCDIR)/unpublishedfile.c
 # this line excludes opcontrol.c and similar files
 EXCLUDE_SRC_FROM_LIB+=$(foreach file, $(SRCDIR)/main,$(foreach cext,$(CEXTS),$(file).$(cext)) $(foreach cxxext,$(CXXEXTS),$(file).$(cxxext)))

include/units/units.hpp

@@ -85,7 +85,7 @@ class Quantity {
         requires std::is_same_v<Self, Dimensionless>
         : value(value) {}
 
-    constexpr operator double()
+    constexpr operator double() const
         requires std::is_same_v<Self, Dimensionless>
     {
         return value;

src/main.cpp

@@ -34,6 +34,9 @@ constexpr void numberOperatorTests() {
     Number c = 1 / Number(2);
     Number d = Number(2) / 2;
     auto e = 1 / 1_in;
+    auto f = 0 == Number(2);
+    auto g = 0 != Number(2);
+    auto h = Number(2) != 0;
 }
 
 constexpr void miscTests() {