From ac3d13839cd797d2992d9111a16b649668e2f06d Mon Sep 17 00:00:00 2001
From: Franklin Wei <git@fwei.tk>
Date: Wed, 11 Nov 2015 11:27:44 -0500
Subject: stuff

---
 src/compile.c | 21 ++++++++++++---------
 src/interp.c  | 36 ++++++++++++++++++++++++++----------
 src/opcodes.h |  1 +
 src/vm.c      | 17 ++++++++++++-----
 4 files changed, 51 insertions(+), 24 deletions(-)

diff --git a/src/compile.c b/src/compile.c
index 1db46af..a5c3f9a 100644
--- a/src/compile.c
+++ b/src/compile.c
@@ -109,6 +109,13 @@ static void setVariable(const char *name, vartype val)
     write_varid(get_varid(name));
 }
 
+static void makeConstantVariable(const char *name, vartype val)
+{
+    write_instr(DECL_CONST);
+    write_varid(get_varid(name));
+    write_imm(val);
+}
+
 static void setConst(const char *name, bool c)
 {
     if(c)
@@ -743,7 +750,7 @@ static vartype eval_expr(char *str)
             }
         }
     }
-
+    
     if(tstart)
     {
         //push_numstack(getValue(tstart, expr));
@@ -1210,14 +1217,10 @@ void ducky_compile(int fd, bool verbose, int out)
 
     /* initialize some other constants */
 
-    setVariable(".", 0);
-    setConst(".", true);
-
-    setVariable("true", 1);
-    setConst("true", true);
-
-    setVariable("false", 0);
-    setConst("false", true);
+    makeConstantVariable(".", 0);
+    
+    makeConstantVariable("true", 1);
+    makeConstantVariable("false", 0);
 
     /* initialize labels (using output from index_lines) */
     index_labels(file_des);
diff --git a/src/interp.c b/src/interp.c
index 41b778a..9a53c22 100644
--- a/src/interp.c
+++ b/src/interp.c
@@ -46,6 +46,8 @@ static off_t *line_offset = NULL;
 
 static unsigned lines_executed = 0, current_line = 0, num_lines;
 
+static unsigned repeat_line;
+
 static unsigned call_stack[CALL_STACK_SZ];
 static unsigned stack_frame = 0;
 
@@ -843,18 +845,31 @@ static int let_handler(char **save, int *repeats_left)
 
 static int repeat_handler(char **save, int *repeats_left)
 {
-    (void) save; (void) repeats_left;
-    char *tok = strtok_r(NULL, ";", save);
-    if(tok)
+    (void) save;
+    if(*repeats_left > 0)
     {
-        if(current_line == 1)
-            error("REPEAT without a previous instruction");
-        *repeats_left = eval_expr(tok) - 1;
-        jump_line(file_des, current_line - 1);
-        return NEXT;
+        --(*repeats_left);
+        if(*repeats_left)
+            jump_line(file_des, repeat_line);
     }
     else
-        error("expected valid expression after REPEAT");
+    {
+        char *tok = strtok_r(NULL, ";", save);
+        if(tok)
+        {
+            if(current_line == 1)
+                error("REPEAT without a previous instruction");
+            *repeats_left = eval_expr(tok) - 1;
+            if(*repeats_left)
+            {
+                repeat_line = current_line - 1;
+                jump_line(file_des, repeat_line);
+            }
+        }
+        else
+            error("expected valid expression after REPEAT");
+    }
+    return NEXT;
 }
 
 static int goto_handler(char **save, int *repeats_left)
@@ -1304,7 +1319,7 @@ void ducky_main(int fd, bool verbose)
             }
         } while(tok);
     break_out:
-
+        #if 0
         if(repeats_left > 0)
         {
             --repeats_left;
@@ -1317,6 +1332,7 @@ void ducky_main(int fd, bool verbose)
                 jump_line(file_des, current_line + 2);
             }
         }
+        #endif
     next_line:
         ;
     }
diff --git a/src/opcodes.h b/src/opcodes.h
index 503ab59..a08157b 100644
--- a/src/opcodes.h
+++ b/src/opcodes.h
@@ -37,4 +37,5 @@
 #define LSH        0x24
 #define RSH        0x25
 #define SQRT       0x26
+#define DECL_CONST 0x27
 #define LINEMARK   0xFF
diff --git a/src/vm.c b/src/vm.c
index e4acc04..aae97af 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -138,8 +138,10 @@ static inline vartype getvar(varid_t varid)
 
 static inline void setvar(varid_t varid, vartype val)
 {
-    if(varid < ARRAYLEN(vars))
+    if(varid < ARRAYLEN(vars) && !vars[varid].constant)
         vars[varid].val = val;
+    else
+        error("cannot modify variable");
 }
 
 static inline void mkconst(varid_t varid)
@@ -267,11 +269,8 @@ void logascii_handler(void)
     vid_writef("%c", pop());
 }
 
-#define CHECKSTACK(x) if(stack_pointer<x)error("not enough elements on stack");
-
 void neg_handler(void)
 {
-    CHECKSTACK(1);
     stack[stack_pointer - 1] = -stack[stack_pointer - 1];
 }
 
@@ -428,6 +427,14 @@ void sqrt_handler(void)
     push(sqrt(pop()));
 }
 
+void decl_const(void)
+{
+    /* no checking, only the compiler can output this instruction */
+    varid_t varid = read_varid();
+    vars[varid].val = read_imm();
+    vars[varid].constant = true;
+}
+
 void inc_line_pointer(void)
 {
     ++current_line;
@@ -488,7 +495,7 @@ static void (*instr_tab[0x100])(void) = {
     lsh_handler,       /*  0x24  */
     rsh_handler,       /*  0x25  */
     sqrt_handler,      /*  0x26  */
-    NULL,              /*  0x27  */
+    decl_const,        /*  0x27  */
     NULL,              /*  0x28  */
     NULL,              /*  0x29  */
     NULL,              /*  0x2a  */
-- 
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