docs: add tutorial

1 files changed, 46 insertions, 0 deletions

diff --git a/tutorial/03_variables.sfinae b/tutorial/03_variables.sfinae
new file mode 100644
index 0000000..6f200f1
--- /dev/null
+++ b/tutorial/03_variables.sfinae
@@ -0,0 +1,46 @@
+// lesson 3: variables
+//
+// a name is a list of characters. a variable holds a type, not a value, and the
+// only type that carries a value is ::decltype(...). the ::conditional_t around
+// it is not required. it is just what everyone does
+
+::declare<
+    ::name<'x'>,
+    ::conditional_t<
+        ::true_type::value,
+        ::decltype(::difference<'F', 'A'>),
+        ::void
+    >
+>::commit;
+
+// reading it back is ::value_of<NAME>, which is a value, so ::decltype it again
+
+::emit<::decltype(::value_of<::name<'x'>>)>::commit;
+
+::declare<
+    ::name<'y'>,
+    ::decltype(
+        ::sum<
+            ::value_of<::name<'x'>>,
+            ::difference<'B', 'A'>
+        >
+    )
+>::commit;
+
+::emit<::decltype(::value_of<::name<'y'>>)>::commit;
+
+// there is no assignment. to change x, undeclare it and declare it again
+
+::undeclare<::name<'x'>>::commit;
+
+::declare<
+    ::name<'x'>,
+    ::decltype(
+        ::product<
+            ::value_of<::name<'y'>>,
+            ::difference<'C', 'A'>
+        >
+    )
+>::commit;
+
+::emit<::decltype(::value_of<::name<'x'>>)>::commit;