diff options
| -rw-r--r-- | users/tazjin/nisp/transform.el | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/users/tazjin/nisp/transform.el b/users/tazjin/nisp/transform.el new file mode 100644 index 000000000000..89b2bb104d27 --- /dev/null +++ b/users/tazjin/nisp/transform.el @@ -0,0 +1,137 @@ +;; Nix as a Lisp + +(require 'cl-lib) +(require 'json) +(require 's) +(require 'dash) + +(defun nisp/expr (form) + "Entrypoint for Nisp->Nix transformation. Will translate FORM +into Nix code, if it is a valid Nisp expression. + +To make code generation slightly easier, each +expression (including literals) is wrapped in an extra pair of +parens." + (concat + "(" + (pcase form + ;; Special keywords + ('() "null") + (`(let . ,rest) (nisp/let form)) + (`(fn . ,rest) (nisp/fn form)) + (`(if ,cond ,then ,else) (nisp/if cond then else)) + + ;; Nix operators & builtins that need special handling + (`(or ,lhs ,rhs) (nisp/infix "||" lhs rhs)) + (`(and ,lhs ,rhs) (nisp/infix "&&" lhs rhs)) + (`(> ,lhs ,rhs) (nisp/infix ">" lhs rhs)) + (`(< ,lhs ,rhs) (nisp/infix "<" lhs rhs)) + (`(>= ,lhs ,rhs) (nisp/infix ">=" lhs rhs)) + (`(<= ,lhs ,rhs) (nisp/infix "<=" lhs rhs)) + (`(+ ,lhs ,rhs) (nisp/infix "+" lhs rhs)) + (`(- ,lhs ,rhs) (nisp/infix "-" lhs rhs)) + (`(* ,lhs ,rhs) (nisp/infix "*" lhs rhs)) + (`(/ ,lhs ,rhs) (nisp/infix "/" lhs rhs)) + (`(-> ,lhs ,rhs) (nisp/infix "->" lhs rhs)) + (`(? ,lhs ,rhs) (nisp/infix "?" lhs rhs)) + (`(// ,lhs ,rhs) (nisp/infix "//" lhs rhs)) + (`(++ ,lhs ,rhs) (nisp/infix "++" lhs rhs)) + (`(== ,lhs ,rhs) (nisp/infix "==" lhs rhs)) + (`(!= ,lhs ,rhs) (nisp/infix "!=" lhs rhs)) + (`(! ,term) (concat "!" (nisp/expr term))) + (`(- ,term) (concat "-" (nisp/expr term))) + + ;; Attribute sets + (`(attrs . ,rest) (nisp/attribute-set form)) + + ;; Function calls + ((and `(,func . ,args) + (guard (symbolp func))) + (nisp/funcall func args)) + + ;; Primitives + ((pred stringp) (json-encode-string form)) + ((pred numberp) (json-encode-number form)) + ((pred keywordp) (substring (symbol-name form) 1)) + ((pred symbolp) (symbol-name form)) + + ;; Lists + ((pred arrayp) (nisp/list form)) + + (other (error "Encountered unhandled form: %s" other))) + ")")) + +(defun nisp/infix (op lhs rhs) + (concat (nisp/expr lhs) " " op " " (nisp/expr rhs))) + +(defun nisp/funcall (func args) + (concat (symbol-name func) " " (s-join " " (-map #'nisp/expr args)))) + +(defun nisp/let (form) + (pcase form + (`(let . (,bindings . (,body . ()))) (concat "let " + (nisp/let bindings) + (nisp/expr body))) + (`((:inherit . ,inherits) . ,rest) (concat (nisp/inherit (car form)) + " " + (nisp/let rest))) + (`((,name . (,value . ())) .,rest) (concat (symbol-name name) " = " + (nisp/expr value) "; " + (nisp/let rest))) + ('() "in ") + (other (error "malformed form '%s' in let expression" other)))) + +(defun nisp/inherit (form) + (pcase form + (`(:inherit . ,rest) (concat "inherit " (nisp/inherit rest))) + (`((,source) . ,rest) (concat "(" (symbol-name source) ") " (nisp/inherit rest))) + (`(,item . ,rest) (concat (symbol-name item) " " (nisp/inherit rest))) + ('() ";"))) + +(defun nisp/if (cond then else) + (concat "if " (nisp/expr cond) + " then " (nisp/expr then) + " else " (nisp/expr else))) + +(defun nisp/list (form) + (cl-check-type form array) + (concat "[ " + (mapconcat #'nisp/expr form " ") + "]")) + + +(defun nisp/attribute-set (form) + "Attribute sets have spooky special handling because they are +not supported by the reader." + (pcase form + (`(attrs . ,rest) (concat "{ " (nisp/attribute-set rest))) + ((and `(,name . (,value . ,rest)) + (guard (keywordp name))) + (concat (substring (symbol-name name) 1) " = " + (nisp/expr value) "; " + (nisp/attribute-set rest))) + ('() "}"))) + +(defun nisp/fn (form) + (pcase form + (`(fn ,args ,body) (concat + (cl-loop for arg in args + concat (format "%s: " arg)) + (nisp/expr body))))) + +;; The following functions are not part of the transform. + +(defun nisp/eval (form) + (interactive "sExpression: ") + (when (stringp form) + (setq form (read form))) + + (message + ;; TODO(tazjin): Construct argv manually to avoid quoting issues. + (s-chomp + (shell-command-to-string + (concat "nix-instantiate --eval -E '" (nisp/expr form) "'"))))) + +(defun nisp/eval-last-sexp () + (interactive) + (nisp/eval (edebug-last-sexp))) |