feat: add functions with defines params and return

1 files changed, 55 insertions, 0 deletions

diff --git a/examples/functions.sfinae b/examples/functions.sfinae
new file mode 100644
index 0000000..d73261f
--- /dev/null
+++ b/examples/functions.sfinae
@@ -0,0 +1,55 @@
+// a function takes types and gives back a type. calling one is itself a type
+// it sees nothing but its parameters, and every argument must be a ::decltype so it carries a value
+
+::define<
+    ::name<'s', 'q', 'u', 'a', 'r', 'e'>,
+    ::parameters<::name<'x'>>,
+    ::sequence<
+        ::return<::decltype(::product<::value_of<::name<'x'>>, ::value_of<::name<'x'>>>)>::commit
+    >
+>::commit;
+
+::emit<
+    ::invoke_result_t<
+        ::name<'s', 'q', 'u', 'a', 'r', 'e'>,
+        ::arguments<::decltype(::difference<'F', 'A'>)>
+    >
+>::commit;
+
+// a function can return anything a type can be, which includes a tuple of characters
+::define<
+    ::name<'g', 'r', 'e', 'e', 't'>,
+    ::parameters<>,
+    ::sequence<
+        ::return<
+            ::tuple<
+                ::integral_constant<::char, ::difference<'h', '\0'>>,
+                ::integral_constant<::char, ::difference<'e', '\0'>>,
+                ::integral_constant<::char, ::difference<'y', '\0'>>
+            >
+        >::commit
+    >
+>::commit;
+
+::emit<::invoke_result_t<::name<'g', 'r', 'e', 'e', 't'>, ::arguments<>>>::commit;
+
+// a function that never returns gives back ::void, and emitting ::void prints nothing
+::define<::name<'n', 'o', 'p'>, ::parameters<>, ::sequence<>>::commit;
+::emit<::invoke_result_t<::name<'n', 'o', 'p'>, ::arguments<>>>::commit;
+
+// a return inside a branch still leaves the function
+::define<
+    ::name<'s', 'i', 'g', 'n'>,
+    ::parameters<::name<'n'>>,
+    ::sequence<
+        ::enable_if_t<
+            ::less<::value_of<::name<'n'>>, ::difference<'A', 'A'>>::value,
+            ::sequence<::return<::decltype(::difference<'A', 'B'>)>::commit>
+        >::commit,
+        ::return<::decltype(::difference<'B', 'A'>)>::commit
+    >
+>::commit;
+
+::emit<
+    ::invoke_result_t<::name<'s', 'i', 'g', 'n'>, ::arguments<::decltype(::difference<'A', 'Z'>)>>
+>::commit;