From 6c903db758ad5440d6352e7f9253c933ebaa7aeb Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Wed, 16 Oct 2013 17:42:47 +0900
Subject: [PATCH] if syntax

---
 include/picrin.h      |  2 +-
 include/picrin/irep.h |  2 ++
 src/state.c           |  1 +
 src/vm.c              | 37 ++++++++++++++++++++++++++++++++++++-
 4 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/include/picrin.h b/include/picrin.h
index de4fb8f9..6ae5eef3 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -23,7 +23,7 @@ typedef struct {
   pic_callinfo *ci;
   pic_callinfo *cibase, *ciend;
 
-  pic_value sDEFINE, sLAMBDA, sCONS;
+  pic_value sDEFINE, sLAMBDA, sIF, sCONS;
   pic_value sADD, sSUB, sMUL, sDIV;
   struct pic_env *global_env;
 
diff --git a/include/picrin/irep.h b/include/picrin/irep.h
index 47e311c9..d01315ff 100644
--- a/include/picrin/irep.h
+++ b/include/picrin/irep.h
@@ -9,6 +9,8 @@ enum pic_instruction {
   OP_GREF,
   OP_GSET,
   OP_LREF,
+  OP_JMP,
+  OP_JMPIF,
   OP_CALL,
   OP_RET,
   OP_LAMBDA,
diff --git a/src/state.c b/src/state.c
index fe21d27b..48740e64 100644
--- a/src/state.c
+++ b/src/state.c
@@ -47,6 +47,7 @@ pic_open()
 
   pic->sDEFINE = pic_intern_cstr(pic, "define");
   pic->sLAMBDA = pic_intern_cstr(pic, "lambda");
+  pic->sIF = pic_intern_cstr(pic, "if");
   pic->sCONS = pic_intern_cstr(pic, "cons");
   pic->sADD = pic_intern_cstr(pic, "+");
   pic->sSUB = pic_intern_cstr(pic, "-");
diff --git a/src/vm.c b/src/vm.c
index be0beece..4f258cb4 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -210,10 +210,11 @@ static struct pic_irep *pic_gen_lambda(pic_state *, pic_value, struct pic_env *)
 static void
 pic_gen(pic_state *pic, struct pic_irep *irep, pic_value obj, struct pic_env *env)
 {
-  pic_value sDEFINE, sLAMBDA, sCONS, sADD, sSUB, sMUL, sDIV;
+  pic_value sDEFINE, sLAMBDA, sIF, sCONS, sADD, sSUB, sMUL, sDIV;
 
   sDEFINE = pic->sDEFINE;
   sLAMBDA = pic->sLAMBDA;
+  sIF = pic->sIF;
   sCONS = pic->sCONS;
   sADD = pic->sADD;
   sSUB = pic->sSUB;
@@ -268,6 +269,26 @@ pic_gen(pic_state *pic, struct pic_irep *irep, pic_value obj, struct pic_env *en
       pic->irep[pic->ilen++] = pic_gen_lambda(pic, obj, env);
       break;
     }
+    else if (pic_eq_p(pic, proc, sIF)) {
+      int s,t;
+
+      pic_gen(pic, irep, pic_car(pic, pic_cdr(pic, obj)), env);
+
+      irep->code[irep->clen].insn = OP_JMPIF;
+      s = irep->clen++;
+
+      /* if false branch */
+      pic_gen(pic, irep, pic_car(pic, pic_cdr(pic, pic_cdr(pic, pic_cdr(pic, obj)))), env);
+      irep->code[irep->clen].insn = OP_JMP;
+      t = irep->clen++;
+
+      irep->code[s].u.i = irep->clen - s;
+
+      /* if true branch */
+      pic_gen(pic, irep, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))), env);
+      irep->code[t].u.i = irep->clen - t;
+      break;
+    }
     else if (pic_eq_p(pic, proc, sCONS)) {
       pic_gen(pic, irep, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))), env);
       pic_gen(pic, irep, pic_car(pic, pic_cdr(pic, obj)), env);
@@ -465,6 +486,20 @@ pic_run(pic_state *pic, struct pic_proc *proc, pic_value args)
       PUSH(pic->ci[-1].sp[pc->u.i]);
       NEXT;
     }
+    CASE(OP_JMP) {
+      pc += pc->u.i;
+      JUMP;
+    }
+    CASE(OP_JMPIF) {
+      pic_value v;
+
+      v = POP();
+      if (! pic_false_p(v)) {
+	pc += pc->u.i;
+	JUMP;
+      }
+      NEXT;
+    }
     CASE(OP_CALL) {
       pic_value c, v;
       struct pic_proc *proc;