From 409ace23eaa92a05f2f9289f7e9a69d6b0c3f821 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Mon, 15 May 2017 20:39:51 -0700
Subject: less table robust against type renumbering.

* lib.c (less_tab_init): The type_prec table initialization
will become incorrect if new type enums are added other than
at the end. Let's switch to assignments. Anything not
mentioned is zero.

* lib.h: Add more advice to comment about extending type_t:
consider all places where MAX_TYPE is used.
---
 lib.c | 33 ++++++++++++++-------------------
 lib.h |  2 +-
 2 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/lib.c b/lib.c
index 6939f817..7e79297a 100644
--- a/lib.c
+++ b/lib.c
@@ -4406,25 +4406,20 @@ static enum less_handling less_tab[MAXTYPE+1][MAXTYPE+1];
 static void less_tab_init(void)
 {
   int l, r;
-  static int type_prec[MAXTYPE+1] = {
-    4, /* NIL */
-    1, /* NUM */
-    1, /* CHR */
-    3, /* LIT */
-    5, /* CONS */
-    3, /* STR */
-    4, /* SYM */
-    0, /* PKG */
-    0, /* FUN */
-    6, /* VEC */
-    5, /* LCONS */
-    3, /* LSTR */
-    0, /* COBJ */
-    0, /* ENV */
-    1, /* BGNUM */
-    1, /* FLNUM */
-    2, /* RNG */
-  };
+  static int type_prec[MAXTYPE+1];
+
+  type_prec[NIL] = 4;
+  type_prec[NUM] = 1;
+  type_prec[CHR] = 1;
+  type_prec[LIT] = 3;
+  type_prec[CONS] = 5;
+  type_prec[STR] = 3;
+  type_prec[SYM] = 4;
+  type_prec[LCONS] = 5;
+  type_prec[LSTR] = 3;
+  type_prec[BGNUM] = 1;
+  type_prec[FLNUM] = 1;
+  type_prec[RNG] = 2;
 
   for (l = 0; l <= MAXTYPE; l++)
     for (r = 0; r <= MAXTYPE; r++) {
diff --git a/lib.h b/lib.h
index 301e46c4..04440b39 100644
--- a/lib.h
+++ b/lib.h
@@ -61,7 +61,7 @@ typedef enum type {
   NIL = TAG_PTR, NUM = TAG_NUM, CHR = TAG_CHR, LIT = TAG_LIT, CONS,
   STR, SYM, PKG, FUN, VEC, LCONS, LSTR, COBJ, ENV,
   BGNUM, FLNUM, RNG, BUF, MAXTYPE = BUF
-  /* If extending, check TYPE_SHIFT */
+  /* If extending, check TYPE_SHIFT and all ocurrences of MAX_TYPE */
 } type_t;
 
 #define TYPE_SHIFT 5
-- 
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