From c25d7ca5386582feba3d02f69a7425ea5b868bc7 Mon Sep 17 00:00:00 2001
From: Kaz Wesley <keziahw@gmail.com>
Date: Thu, 18 Jan 2018 16:28:42 -0800
Subject: [PATCH] read: implement basic decimal FIXes

Implement read for FIXes of the form /-?[0-9]+/

Signed-off-by: Kaz Wesley <keziahw@gmail.com>
---
 doc/ROADMAP.md |  1 +
 src/object.h   | 16 +++++++---
 src/print.c    |  4 +--
 src/read.c     | 80 +++++++++++++++++++++++++++++++++++++++++++-------
 4 files changed, 85 insertions(+), 16 deletions(-)

diff --git a/doc/ROADMAP.md b/doc/ROADMAP.md
index be3251b..d4e961f 100644
--- a/doc/ROADMAP.md
+++ b/doc/ROADMAP.md
@@ -4,6 +4,7 @@ Roughly dependency-ordered todo list:
 * [ ] *PROCESS/MCALL*
 * [ ] EVAL; initial interpreter and REPL
 * [ ] atoms, global bindings, normal FUNCTIONs
+* [ ] unit test script prerequisites (assertions, type introspection...)
 * [ ] *GC*
 * [ ] local bindings
 * [ ] control flow
diff --git a/src/object.h b/src/object.h
index 80c886e..b62cacb 100644
--- a/src/object.h
+++ b/src/object.h
@@ -111,14 +111,14 @@ typedef struct
   alignas (16) evaltype type;
   pool_ptr rest;
   uint32_t _pad;
-  uint32_t val;
+  int32_t val;
 } fix32_object;
 
 typedef struct
 {
   alignas (16) evaltype type;
   pool_ptr rest;
-  uint64_t val;
+  int64_t val;
 } fix64_object;
 
 typedef struct
@@ -196,12 +196,20 @@ union object
 Initialization helpers.
 */
 
+static inline fix32_object
+new_fix32 (int32_t n)
+{
+  return (fix32_object)
+  {
+  .type = EVALTYPE_FIX32,.rest = 0,.val = n};
+}
+
 static inline fix64_object
-new_fix64 (uint64_t n)
+new_fix64 (int64_t n)
 {
   return (fix64_object)
   {
-  .type = EVALTYPE_FIX64,.rest = 0,.val = n,};
+  .type = EVALTYPE_FIX64,.rest = 0,.val = n};
 }
 
 static inline list_object
diff --git a/src/print.c b/src/print.c
index 64a6115..539016e 100644
--- a/src/print.c
+++ b/src/print.c
@@ -59,10 +59,10 @@ print_object (const object * o)
   switch (o->type)
     {
     case EVALTYPE_FIX32:
-      printf ("%u", o->fix32.val);
+      printf ("%d", o->fix32.val);
       break;
     case EVALTYPE_FIX64:
-      printf ("%lu", o->fix64.val);
+      printf ("%ld", o->fix64.val);
       break;
     case EVALTYPE_LIST:
       printf ("(");
diff --git a/src/read.c b/src/read.c
index 57dd81f..68efbf3 100644
--- a/src/read.c
+++ b/src/read.c
@@ -113,10 +113,70 @@ static uint32_t obj_get_fix32(const object *o) {
 }
 */
 
+static int
+read_num (const char *p, reader_stack *st)
+{
+  int i = 0;
+  // Use an unsigned intermediate to simplify overflow checks.
+  uint64_t x = 0;
+  // Disallow "number" composed of ancillary number components only.
+  bool gotdigits = false;
+  // Skip for now, later we'll check again to potentially negate.
+  if (p[0] == '-')
+    i++;
+  // TODO: asterisk-deliminated *octal*
+  // TODO: other bases?
+  for (; p[i]; i++)
+    {
+      if (p[i] >= '0' && p[i] <= '9')
+	{
+	  if (x * 10 + (p[i] - '0') < x)
+	    goto read_float;
+	  x = x * 10 + (p[i] - '0');
+	  gotdigits = true;
+	  continue;
+	}
+
+      // TODO: decimal points, exponent notation
+      // NB. a terminal decimal denotes a FIX
+      // NB. exponent notation doesn't necessarily indicate a float
+
+      // TODO: distinguish 'delimiter' characters that terminate
+      // number from 'identifier' chars that cause parsing to fail
+      // (and potentially be parsed as an atom)
+      break;
+    }
+  if (!gotdigits)
+    return 0;
+  if (p[0] != '-')
+    {
+      if (x <= INT32_MAX)
+	(--(st->pos))->fix32 = new_fix32 ((int32_t)x);
+      else if (x <= INT64_MAX)
+	(--(st->pos))->fix64 = new_fix64 (x);
+      else
+	goto read_float;
+    }
+  else
+    {
+      if (-x >= (uint64_t)INT32_MIN)
+	(--(st->pos))->fix32 = new_fix32 (0 - (int32_t)x);
+      else if (-x >= (uint64_t)INT64_MIN)
+	(--(st->pos))->fix64 = new_fix64 (0 - (int64_t)x);
+      else
+	goto read_float;
+    }
+  st->framelen++;
+  return i;
+ read_float:
+  assert(0 && "unimplemented: promote num to float");
+  return i;
+}
+
 // stack[0..len]: objs in current list
 // stack[len]: parent len
 const char *
-read_token (const char *p, reader_stack * st)
+read_token (const char *p, reader_stack *st)
 {
   p += count_whitespace (p);
   switch (p[0])
@@ -191,17 +251,17 @@ read_token (const char *p, reader_stack * st)
 	st->pos->vector = new_vector (h, len);
 	break;
       }
-    case '4':
+    default:
       {
-	p++;
-	// push fix obj, extending frame
-	(--(st->pos))->fix64 = new_fix64 (4);
-	st->framelen++;
-	break;
+	int n = read_num (p, st);
+	if (n)
+	  return p + n;
+
+	// TODO: try read pname
+
+	fprintf (stderr, "read unimplemented for char: '%c'\n", *p);
+	assert (0 && "read unimplemented for char");
       }
-    default:
-      fprintf (stderr, "read unimplemented for char: '%c'\n", *p);
-      assert (0 && "read unimplemented for char");
     }
   return p;
 }
-- 
2.31.1