if-then-else.diff

diff -ru lua-5.1.4/src/lcode.c lua-5.1.4-if/src/lcode.c
--- lua-5.1.4/src/lcode.c	2007-12-29 00:32:24.000000000 +0900
+++ lua-5.1.4-if/src/lcode.c	2010-09-14 17:09:52.960000000 +0900
@@ -411,6 +411,13 @@
 }
 
 
+void luaK_exp2reg (FuncState *fs, expdesc *e, int reg) {
+  luaK_dischargevars(fs, e);
+  freeexp(fs, e);
+  exp2reg(fs, e, reg);
+}
+
+
 void luaK_exp2nextreg (FuncState *fs, expdesc *e) {
   luaK_dischargevars(fs, e);
   freeexp(fs, e);
diff -ru lua-5.1.4/src/lcode.h lua-5.1.4-if/src/lcode.h
--- lua-5.1.4/src/lcode.h	2007-12-27 22:02:26.000000000 +0900
+++ lua-5.1.4-if/src/lcode.h	2010-09-14 17:09:42.241000000 +0900
@@ -52,6 +52,7 @@
 LUAI_FUNC int luaK_numberK (FuncState *fs, lua_Number r);
 LUAI_FUNC void luaK_dischargevars (FuncState *fs, expdesc *e);
 LUAI_FUNC int luaK_exp2anyreg (FuncState *fs, expdesc *e);
+LUAI_FUNC void luaK_exp2reg (FuncState *fs, expdesc *e, int reg);
 LUAI_FUNC void luaK_exp2nextreg (FuncState *fs, expdesc *e);
 LUAI_FUNC void luaK_exp2val (FuncState *fs, expdesc *e);
 LUAI_FUNC int luaK_exp2RK (FuncState *fs, expdesc *e);
diff -ru lua-5.1.4/src/lparser.c lua-5.1.4-if/src/lparser.c
--- lua-5.1.4/src/lparser.c	2010-06-21 11:00:08.596400000 +0900
+++ lua-5.1.4-if/src/lparser.c	2010-09-14 17:09:37.388000000 +0900
@@ -821,8 +821,29 @@
 #define UNARY_PRIORITY	8  /* priority for unary operators */
 
 
+static int cond (LexState *ls);
+static void ifexpr (LexState *ls, expdesc *v) {
+  /* ifexpr -> IF cond THEN expr ELSE expr */
+  FuncState *fs = ls->fs;
+  int condexit;
+  int escapelist = NO_JUMP;
+  int reg;
+  luaX_next(ls);				/* skip IF */
+  condexit = cond(ls);
+  checknext(ls, TK_THEN);
+  expr(ls, v);					/* eval THEN part */
+  reg = luaK_exp2anyreg(fs, v);			/* set result to reg. */
+  luaK_concat(fs, &escapelist, luaK_jump(fs));
+  luaK_patchtohere(fs, condexit);
+  checknext(ls, TK_ELSE);
+  expr(ls, v);					/* eval ELSE part */
+  luaK_exp2reg(fs, v, reg);			/* set result to reg. */
+  luaK_patchtohere(fs, escapelist);
+}
+
+
 /*
-** subexpr -> (simpleexp | unop subexpr) { binop subexpr }
+** subexpr -> (simpleexp | ifexpr | unop subexpr) { binop subexpr }
 ** where `binop' is any binary operator with a priority higher than `limit'
 */
 static BinOpr subexpr (LexState *ls, expdesc *v, unsigned int limit) {
@@ -834,7 +855,7 @@
     luaX_next(ls);
     subexpr(ls, v, UNARY_PRIORITY);
     luaK_prefix(ls->fs, uop, v);
-  }
+  } else if (ls->t.token == TK_IF) ifexpr(ls, v);
   else simpleexp(ls, v);
   /* expand while operators have priorities higher than `limit' */
   op = getbinopr(ls->t.token);