From: Tim Vaughan <tgvaughan@gmail.com>
Date: Sun, 12 Jun 2016 08:28:59 +0000 (+1200)
Subject: Fiddling with parser (reader?)
X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=commitdiff_plain;h=123ce52c0fe63b568a3c9c11dc1b85d4dfd17c8e;p=scheme.forth.jl.git

Fiddling with parser (reader?)
---

diff --git a/scheme.4th b/scheme.4th
index 65c64a8..48ab564 100644
--- a/scheme.4th
+++ b/scheme.4th
@@ -19,6 +19,16 @@ create types memsize allot
 variable nextfree
 0 nextfree !
 
+: make-bool 
+    nextfree @
+
+    car nextfree @ + !
+    cdr nextfree @ + 0 !
+    types nextfree @ + bool-type !
+
+    1 nextfree +!
+;
+
 : stack
     create here 1+ , allot ;
 
@@ -80,25 +90,36 @@ variable parse-str
 
 : parsebool
 
-    nextchar emit cr
-    trace
-
-    false
-    nextchar [char] # <> if exit then
+    nextchar [char] # <> if false exit then
 
     1 inc-parse-idx
 
     nextchar dup [char] t = swap [char] f = or
     not if
         1 dec-parse-idx
-        exit
+        false exit
     then
 
     1 inc-parse-idx
 
     ?delim not if
         2 dec-parse-idx
-        exit
+        false exit
+    else
+        1 dec-parse-idx
+        nextchar [char] t = make-bool
+        1 inc-parse-idx
+        true exit
+    then
+;
+
+\ Set cdr at i to j, leaving j on the stack
+: append ( i j -- j )
+    dup rot
+    dup 0> if
+        cdr + !
+    else
+        2drop
     then
 ;
 
@@ -119,8 +140,9 @@ variable parse-str
     then
 
     parsebool if
+        append
         exit
-    exit
+    then
 ;
 
 \ Parse a counted string into a scheme expression