From 1a6c8a3cca5059576b7fa1d8366b4144f5219176 Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Thu, 17 Oct 2013 20:48:50 +0900
Subject: [PATCH] support multi-line input in REPL

---
 include/picrin.h |  2 +-
 src/main.c       | 30 +++++++++++++++++++++---------
 src/parse.y      | 30 ++++++++++++++++++++++++++----
 3 files changed, 48 insertions(+), 14 deletions(-)

diff --git a/include/picrin.h b/include/picrin.h
index a83b1df9..06d08720 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -61,7 +61,7 @@ bool pic_eq_p(pic_state *, pic_value, pic_value);
 
 pic_value pic_intern_cstr(pic_state *, const char *);
 
-pic_value pic_parse(pic_state *, const char *);
+bool pic_parse(pic_state *, const char *, pic_value *);
 
 pic_value pic_eval(pic_state *, pic_value, struct pic_env *);
 pic_value pic_run(pic_state *, struct pic_proc *, pic_value);
diff --git a/src/main.c b/src/main.c
index 1e24ed3f..07f3edc3 100644
--- a/src/main.c
+++ b/src/main.c
@@ -31,17 +31,20 @@ test_object_creation(pic_state *pic)
   }
 }
 
+#define CODE_MAX_LENGTH 1024
 #define LINE_MAX_LENGTH 256
 
 int
 main()
 {
   pic_state *pic;
-  char line[LINE_MAX_LENGTH], last_char, *read_line;
+  char code[CODE_MAX_LENGTH] = "", line[LINE_MAX_LENGTH];
+  char last_char, *read_line, *prompt;
   int char_index;
   pic_value v;
   struct pic_proc *proc;
   int ai;
+  bool r;
 
   pic = pic_open();
 
@@ -52,9 +55,10 @@ main()
   ai = pic_gc_arena_preserve(pic);
 
   while (1) {
+    prompt = code[0] == '\0' ? "> " : "* ";
 
 #if PIC_ENABLE_READLINE
-    read_line = readline("> ");
+    read_line = readline(prompt);
     if (read_line == NULL) {
       line[0] = '\0';
     }
@@ -64,7 +68,7 @@ main()
       free(read_line);
     }
 #else
-    printf("> ");
+    printf(prompt);
 
     char_index = 0;
     while ((last_char = getchar()) != '\n') {
@@ -77,8 +81,21 @@ main()
     line[char_index] = '\0';
 #endif
 
+    if (strlen(code) + strlen(line) >= CODE_MAX_LENGTH)
+      goto overflow;
+    strcat(code, line);
+
     /* read */
-    v = pic_parse(pic, line);
+    r = pic_parse(pic, code, &v);
+    if (! r) {			/* wait for more input */
+      pic_gc_arena_restore(pic, ai);
+      continue;
+    }
+    code[0] = '\0';
+    if (pic_undef_p(v)) {	/* parse error */
+      pic_gc_arena_restore(pic, ai);
+      continue;
+    }
 
 #if DEBUG
     printf("[read: ");
@@ -86,11 +103,6 @@ main()
     printf("]\n");
 #endif
 
-    if (pic_undef_p(v)) {
-      pic_gc_arena_restore(pic, ai);
-      continue;
-    }
-
     /* eval */
     proc = pic_codegen(pic, v, pic->global_env);
     v = pic_run(pic, proc, pic_nil_value());
diff --git a/src/parse.y b/src/parse.y
index 1875d9d2..8c1176d7 100644
--- a/src/parse.y
+++ b/src/parse.y
@@ -9,6 +9,7 @@
 struct parser_control {
   pic_state *pic;
   pic_value value;
+  bool incomp;
 };
 
 %}
@@ -31,12 +32,17 @@ struct parser_control {
 program
 	:
 	{
-	  p->value = pic_undef_value(p->pic);
+	  p->value = pic_undef_value();
 	}
 	| datum
 	{
 	  p->value = $1;
 	}
+	| incomplete_datum
+	{
+	  p->incomp = true;
+	  p->value = pic_undef_value();
+	}
 ;
 
 datum
@@ -91,6 +97,18 @@ list_data
 	}
 ;
 
+incomplete_datum
+	: tLPAREN incomplete_data
+;
+
+incomplete_data
+	:  /* none */
+	| datum tDOT
+	| datum incomplete_datum
+	| datum tDOT incomplete_datum
+	| datum incomplete_data
+;
+
 %%
 
 int
@@ -99,12 +117,13 @@ yyerror(struct parser_control *p, const char *msg)
   puts(msg);
 }
 
-pic_value
-pic_parse(pic_state *pic, const char *str)
+bool
+pic_parse(pic_state *pic, const char *str, pic_value *v)
 {
   struct parser_control p;
 
   p.pic = pic;
+  p.incomp = false;
 
   yy_scan_string(str);
   yyparse(&p);
@@ -114,5 +133,8 @@ pic_parse(pic_state *pic, const char *str)
     p.value = pic_undef_value();
   }
 
-  return p.value;
+  if (! p.incomp) {
+    *v = p.value;
+  }
+  return ! p.incomp;
 }