EdnProvide

input/src/edn_provide.rs

@@ -0,0 +1,25 @@
+use crate::*;
+
+/// Implement `EdnProvide` for a type and context
+#[macro_export] macro_rules! edn_provide {
+    ($type:ty:|$self:ident:$State:ty|{ $($pat:pat => $expr:expr),* $(,)? }) => {
+        impl EdnProvide<$type> for $State {
+            fn get <S: AsRef<str>> (&$self, edn: &EdnItem<S>) -> Option<$type> {
+                Some(match edn.to_ref() {
+                    $(EdnItem::Sym($pat) => $expr),*,
+                    _ => return None
+                })
+            }
+        }
+    }
+}
+
+/// Map EDN tokens to parameters of a given type for a given context
+pub trait EdnProvide<U> {
+    fn get <S: AsRef<str>> (&self, _edn: &EdnItem<S>) -> Option<U> {
+        None
+    }
+    fn get_or_fail <S: AsRef<str>> (&self, edn: &EdnItem<S>) -> U {
+        self.get(edn).expect("no value")
+    }
+}