From: Luke Lau <luke_lau@icloud.com>
Date: Mon, 29 Jul 2019 12:44:23 +0000 (+0100)
Subject: Add ast-find
X-Git-Url: http://git.lukelau.me/?p=scheme.git;a=commitdiff_plain;h=8b8c603a6106151188bdeab95501cacaf72912d4

Add ast-find
---

diff --git a/ast.scm b/ast.scm
index a38a012..2beb945 100644
--- a/ast.scm
+++ b/ast.scm
@@ -48,6 +48,28 @@
 		 (fold-map inner (cdr x)))]
     [else (f x)]))
 
+(define (ast-find p x)
+  (define (inner y) (ast-find p y))
+  (define (any p x) (fold-left
+		     (lambda (acc y) (if acc #t (p y)))
+		     #f
+		     x))
+  (define (either . fs)
+    (if (null? fs) #f
+	(if (car fs) (car fs)
+	    (apply either (cdr fs)))))
+		     
+  (case (ast-type x)
+    ['let (either (p x)
+		  (any inner (let-bindings x))
+		  (any inner (let-body x)))]
+    ['app (either (p x)
+		  (any inner x))]
+    ['lambda (either (p x)
+		     (inner (lambda-body x)))]
+    ['if (either (p x) (any inner (cdr x)))]
+    [else (p x)]))
+
 (define let-bindings cadr)
 (define let-body cddr)