From 572d95f1082c571a894e73dc8908f5ab39b0b0a2 Mon Sep 17 00:00:00 2001
From: Yiyun Liu <yliu8e5f7@protonmail.com>
Date: Sun, 25 May 2025 01:21:39 -0400
Subject: [PATCH] Forgot to commit

---
 printer.rkt | 118 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 printer.rkt

diff --git a/printer.rkt b/printer.rkt
new file mode 100644
index 0000000..7de8dad
--- /dev/null
+++ b/printer.rkt
@@ -0,0 +1,118 @@
+#lang typed/racket
+(require "ast.rkt")
+
+(define-type IndentLevel Nonnegative-Integer)
+
+(define-type ISeq
+  (∪ Null String (List 'Indent ISeq) 'Newline (List '++ ISeq ISeq)))
+
+(define-syntax iseq-append-with-sep
+  (syntax-rules ()
+    [(iseq-append-with-sep _) '()]
+    [(iseq-append-with-sep _ a) a]
+    [(iseq-append-with-sep sep a b c ...)
+     (iseq-append a sep (iseq-append-with-sep sep b c ...) )]))
+
+(: seq (-> ISeq ISeq ISeq))
+(define (seq a b)
+  (match (list a b)
+    [`(() ,b) b]
+    [`(,a ()) a]
+    [_ (list '++ a b)]))
+
+(define-syntax iseq-append
+  (syntax-rules ()
+    [(iseq-append a b) (seq a b)]
+    [(iseq-append a b c ...) (seq a (iseq-append b c ...))]))
+
+(: ppr-list (All (A) (-> (-> A ISeq) ISeq (Listof A) ISeq)))
+(define (ppr-list f sep xs)
+  (match xs
+    ['() '()]
+    [(list x) (f x)]
+    [(list x y xs ...)
+     (iseq-append (f x) sep (ppr-list f sep (cons y xs)))]))
+
+(: ppr-alt (-> CoreAlt ISeq))
+(define (ppr-alt a)
+  (match a
+    [(list 'branch con xs body)
+     (iseq-append-with-sep
+      " "
+      (iseq-append
+       "<"
+       (number->string con)
+       ">")
+      (ppr-list symbol->string " " xs)
+      "->"
+      (ppr-expr body))]))
+
+(: ppr-bind (-> CoreBind ISeq))
+(define (ppr-bind a)
+  (match a
+    [(list x a)
+     (iseq-append-with-sep " " (symbol->string x) "=" (ppr-expr a))]))
+
+(: ppr-binds (-> CoreBinds ISeq))
+(define (ppr-binds a)
+  (ppr-list ppr-bind (iseq-append ";" 'Newline) a))
+
+(: ppr-alts (-> CoreAlts ISeq))
+(define (ppr-alts x) (ppr-list ppr-alt (iseq-append ";" 'Newline) x))
+
+(: ppr-case (-> CoreExpr CoreAlts ISeq))
+(define (ppr-case e alts)
+  (iseq-append
+   (iseq-append-with-sep
+    " "
+    "case"
+    (ppr-expr e)
+    "of")
+   (list 'Indent (list 'Indent
+                       (iseq-append 'Newline (ppr-alts alts))))))
+
+(: ppr-lets (-> Let CoreBinds CoreExpr ISeq))
+(define (ppr-lets lt binds e)
+  (iseq-append
+   (symbol->string lt)
+   " "
+   (list 'Indent (list 'Indent (list 'Indent (list 'Indent (ppr-binds binds)))))
+   'Newline
+   "in "
+   (list 'Indent (list 'Indent (list 'Indent (ppr-expr e))))))
+
+(: ppr-expr (-> CoreExpr ISeq))
+(define (ppr-expr a)
+  (match a
+    [`(,f ,x) (iseq-append (ppr-expr f) " " (ppr-aexpr x))]
+    [(? integer? n) (number->string n)]
+    [(? symbol? x) (symbol->string x)]
+    [`(case ,e ,alts) (ppr-case e alts)]
+    [`(let ,binds ,e) (ppr-lets 'let binds e)]
+    [`(letrec ,binds ,e) (ppr-lets 'letrec binds e)]))
+
+(: ppr-aexpr (-> CoreExpr ISeq))
+(define (ppr-aexpr a)
+  (if (or (integer? a) (symbol? a))
+      (ppr-expr a)
+      (iseq-append "(" (ppr-expr a) ")")))
+
+(: iseq->string (-> IndentLevel ISeq String))
+(define (iseq->string l a)
+  (letrec ([s (open-output-string)]
+           [go : (-> IndentLevel ISeq Void)
+               (λ (l i)
+                 (match i
+                   ['() (void)]
+                   [`(++ ,i0 ,i1) (begin
+                                    (go l i0)
+                                    (go l i1))]
+                   [`(Indent ,i) (go (+ l 1) i)]
+                   ['Newline (display
+                              (string-append
+                               "\n"
+                               (make-string l #\space))
+                              s)]
+                   [(? string?) (display i s)]))])
+    (go l a)
+    (get-output-string s)))