1 files changed, 207 insertions, 0 deletions
diff --git a/src/ast.lisp b/src/ast.lisp
new file mode 100644
index 0000000..c33de88
--- /dev/null
+++ b/src/ast.lisp
@@ -0,0 +1,207 @@
+(in-package :ast)
+
+(defclass node ()
+  ((token :accessor token
+          :initarg :token
+          :type token)))
+
+(defgeneric stringify (node)
+  (:method ((node node))
+    (with-output-to-string (out)
+      (emit node out))))
+
+(defparameter *indent* 0)
+(defun emit-new-line (stream)
+  (write-char #\Newline stream)
+  (loop :for i :from 0 :below *indent*
+        :do (write-char #\Space stream)))
+
+(defgeneric emit (node stream)
+  (:method ((node node) stream)
+    (write-string (token-literal node) stream)))
+
+(defgeneric token-literal (node)
+  (:method ((node node))
+    (token:literal (token node))))
+
+(defclass statement (node)
+  ())
+
+(defclass expression (node)
+  ())
+
+(defclass program (node)
+  ((statements :accessor statements
+               :initform (make-array 10 :adjustable t :fill-pointer 0))))
+
+(defmethod token-literal ((node program))
+  (if (> (length (statements node)) 0)
+      (token-literal (aref (statements node) 0))
+      ""))
+
+(defmethod emit ((node program) stream)
+  (loop :for stmt :across (statements node)
+        :do (emit stmt stream)))
+
+(defclass identifier (expression)
+  ())
+
+(defclass let-statement (statement)
+  ((name :accessor name
+         :initarg :name
+         :type identifier)
+   (value :accessor value
+          :initarg :value
+          :type expression)))
+
+(defmethod emit ((node let-statement) stream)
+  (write-string (token-literal node) stream)
+  (write-char #\Space stream)
+  (emit (name node) stream)
+  (write-string " = " stream)
+  (emit (value node) stream)
+  (write-char #\; stream)
+  (write-char #\Newline stream))
+
+(defclass return-statement (statement)
+  ((return-value :accessor return-value
+                 :initarg :return-value
+                 :type expression)))
+
+(defmethod emit ((node return-statement) stream)
+  (write-string (token-literal node) stream)
+  (write-char #\Space stream)
+  (emit (return-value node) stream)
+  (write-char #\; stream)
+  (write-char #\Newline stream))
+
+(defclass integer-literal (expression)
+  ((value :accessor value
+          :initarg :value
+          :type integer)))
+
+(defclass prefix-expression (expression)
+  ((operator :accessor operator
+             :initarg :operator
+             :type token-type)
+   (right :accessor right
+          :initarg :right
+          :type expression)))
+
+(defmethod emit ((node prefix-expression) stream)
+  (write-char #\( stream)
+  (write-string (token-literal node) stream)
+  (emit (right node) stream)
+  (write-char #\) stream))
+
+
+(defclass expression-statement (statement)
+  ((expression :accessor expression
+               :initarg :expression
+               :type expression)))
+
+(defmethod emit ((node expression-statement) stream)
+  (emit (expression node) stream)
+  (write-char #\; stream)
+  (write-char #\Newline stream))
+
+(defclass boolean-expression (expression)
+  ((value :accessor value
+          :initarg :value
+          :type boolean)))
+
+(defclass infix-expression (expression)
+  ((left :accessor left
+         :initarg :left
+         :type expression)
+   (operator :accessor operator
+             :initarg :operator
+             :type token-type)
+   (right :accessor right
+          :initarg :right
+          :type expression)))
+
+(defmethod emit ((node infix-expression) stream)
+  (write-char #\( stream)
+  (emit (left node) stream)
+  (let ((tok (token:as-token (operator node))))
+    (format stream " ~a " (token:literal tok)))
+  (emit (right node) stream)
+  (write-char #\) stream))
+
+(defclass if-expression (expression)
+  ((con :accessor con
+        :initarg :condition
+        :type expression)
+   (consequence :accessor consequence
+                :initarg :consequence
+                :type block-statement)
+   (alternative :accessor alternative
+                :initform nil
+                :initarg :alternative
+                :type (or block-statement null))))
+
+(defmethod emit ((node if-expression) stream)
+  (write-string "if (" stream)
+  (emit (con node) stream)
+  (write-string ") " stream)
+  (emit (consequence node) stream)
+  (unless (null (alternative node))
+    (write-string "else " stream)
+    (emit (alternative node) stream)))
+
+(defclass block-statement (statement)
+  ((statements :accessor statements
+               :initarg statements
+               :initform (make-array 0 :element-type 'statement
+                                       :adjustable t :fill-pointer 0)
+               :type (vector statement))))
+
+(defmethod emit ((node block-statement) stream)
+  (write-char #\{ stream)
+  (let ((*indent* (+ 4 *indent*)))
+    (emit-new-line stream)
+    (loop :for stmt :across (statements node)
+          :do (emit stmt stream)))
+  (format stream "}"))
+
+(defclass function-literal (expression)
+  ((parameters :accessor parameters
+               :initarg :parameters
+               :initform (make-array 0 :element-type 'identifier
+                                       :adjustable t :fill-pointer 0)
+               :type (vector identifier))
+   (body :accessor body
+         :initarg :body
+         :type block-statement)))
+
+(defmethod emit ((node function-literal) stream)
+  (write-string (token-literal node) stream)
+  (write-char #\( stream)
+  (loop :for param :across (parameters node)
+        :for i :from 1
+        :do (write-string (token-literal param) stream)
+            (when (< i (length (parameters node)))
+              (write-string ", " stream)))
+  (write-char #\) stream)
+  (emit (body node) stream))
+
+(defclass call-expression (expression)
+  ((fn-expr :accessor fn-expr
+            :initarg :function
+            :type expression)
+   (args :accessor args
+         :initarg :args
+         :initform (make-array 0 :element-type 'expression
+                                 :adjustable t :fill-pointer 0)
+         :type (vector expression))))
+
+(defmethod emit ((node call-expression) stream)
+  (emit (fn-expr node) stream)
+  (write-char #\( stream)
+  (loop :for arg :across (args node)
+        :for i :from 1
+        :do (emit arg stream)
+            (when (< i (length (args node)))
+              (write-string ", " stream)))
+  (write-char #\) stream))