From 770767c11e377919e6776c15562b439bf5954e36 Mon Sep 17 00:00:00 2001
From: Simon Brooke <simon@journeyman.cc>
Date: Fri, 20 Jan 2017 12:27:09 +0000
Subject: [PATCH] Now have quote. Everything still seems to work. Unit tests
 still pass.

---
 src/init.c    |  7 +++++++
 src/lispops.c | 13 +++++++++++++
 src/lispops.h |  2 ++
 3 files changed, 22 insertions(+)

diff --git a/src/init.c b/src/init.c
index a5c3c40..237cc03 100644
--- a/src/init.c
+++ b/src/init.c
@@ -36,6 +36,11 @@ int main (int argc, char *argv[]) {
   fprintf( stderr, "Post scarcity software environment version %s\n", VERSION);
   initialise_cons_pages();
 
+  /* privileged variables (keywords) */
+  deep_bind( intern( c_string_to_lisp_string( "nil"), oblist), NIL);
+  deep_bind( intern( c_string_to_lisp_string( "t"), oblist), TRUE);
+
+  /* primitive function operations */
   bind_function( "assoc", &lisp_assoc);
   bind_function( "car", &lisp_car);
   bind_function( "cdr", &lisp_cdr);
@@ -45,8 +50,10 @@ int main (int argc, char *argv[]) {
   bind_function( "read", &lisp_read);
   bind_function( "print", &lisp_print);
 
+  /* primitive special forms */
   bind_special( "apply", &lisp_apply);
   bind_special( "eval", &lisp_eval);
+  bind_special( "quote", &lisp_quote);
 
   fprintf( stderr, "\n:: ");
   struct cons_pointer input = read( stdin);
diff --git a/src/lispops.c b/src/lispops.c
index 6dd4d88..0399b21 100644
--- a/src/lispops.c
+++ b/src/lispops.c
@@ -117,6 +117,7 @@ struct cons_pointer lisp_eval( struct cons_pointer s_expr, struct cons_pointer e
       struct cons_space_object special = pointer2cell( fn_pointer);
       result = (*special.payload.special.executable)( args, env, previous);
     } else if ( functionp( fn_pointer)) {
+      /* actually, this is apply */
       struct cons_space_object function = pointer2cell( fn_pointer);
       struct stack_frame* frame = make_stack_frame( my_frame, args, env);
 
@@ -147,6 +148,18 @@ struct cons_pointer lisp_eval( struct cons_pointer s_expr, struct cons_pointer e
   return result;
 }
 
+/**
+ * (quote a)
+ *
+ * Special form
+ * Returns its argument (strictly first argument - only one is expected but
+ * this isn't at this stage checked) unevaluated.
+ */
+struct cons_pointer lisp_quote( struct cons_pointer args, struct cons_pointer env,
+				struct stack_frame* frame) {
+  return c_car( args);
+}
+
 /**
  * (cons a b)
  *
diff --git a/src/lispops.h b/src/lispops.h
index 1268b7e..597d67f 100644
--- a/src/lispops.h
+++ b/src/lispops.h
@@ -24,6 +24,8 @@ struct cons_pointer lisp_eval( struct cons_pointer args, struct cons_pointer env
 			       struct stack_frame* frame);
 struct cons_pointer lisp_apply( struct cons_pointer args, struct cons_pointer env,
 				struct stack_frame* frame);
+struct cons_pointer lisp_quote( struct cons_pointer args, struct cons_pointer env,
+				struct stack_frame* frame);
 
 /* functions */
 struct cons_pointer lisp_cons( struct stack_frame* frame, struct cons_pointer env);