Notes on Hylang

20210608234049-hy.org

@@ -0,0 +1,59 @@
+#+title: Hy
+
+A lisp dialect of Python.
+
+* Example
+#+name: dataclass
+#+begin_src hy :exports code :eval never
+  (import [dataclasses [dataclass])
+
+  (with-decorator dataclass
+    (defclass Thing []
+      (^str name)
+      (^int age)))
+#+end_src
+
+Disassembling the above code generates the following Python equivalent.
+
+#+begin_src hy :exports results :cache yes :wrap src python
+  (disassemble
+    (quote
+      (do
+        (import [dataclasses [dataclass]])
+
+        (with-decorator dataclass
+          (defclass Thing []
+            (^str description)
+            (^int value)))))
+    True)
+#+end_src
+
+#+RESULTS[08e5153ad26dcf0fd8ca2a7c041eb26268461381]:
+#+begin_src python
+from dataclasses import dataclass
+
+
+@dataclass
+class Thing:
+    description: str
+    value: int
+#+end_src
+
+* Annotations
+Supports [[file:20201007142751-python_typing.org][Python Typing]] annotations via the special form =^=:
+
+#+begin_src hy :exports code :eval never
+  ; Annotate the variable x as an int (equivalent to `x: int`).
+  (^int x)
+  ; Can annotate with expressions if needed (equivalent to `y: f(x)`).
+  (^(f x) y)
+
+  ; Annotations with an assignment: each annotation (int, str) covers the term that
+  ; immediately follows.
+  ; Equivalent to: x: int = 1; y = 2; z: str = 3
+  (setv ^int x 1 y 2 ^str z 3)
+
+  ; Annotate a as an int, c as an int, and b as a str.
+  ; Equivalent to: def func(a: int, b: str = None, c: int = 1): ...
+  (defn func [^int a ^str [b None] ^int [c 1]] ...)
+#+end_src