From 618de4c70d8916f64781997f3ae538e3e6109d00 Mon Sep 17 00:00:00 2001
From: Ben Winston
Date: Sun, 21 May 2023 16:20:41 -0400
Subject: if/else, 'and' control flow

---
 vm.d | 66 +++++++++++++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 45 insertions(+), 21 deletions(-)

(limited to 'vm.d')

diff --git a/vm.d b/vm.d
index 99016f2..45f3742 100644
--- a/vm.d
+++ b/vm.d
@@ -31,7 +31,6 @@ class VM {
     
     Value peekA(int offset) {
         if (offset >= aTop) {
-        //if (offset > this.topOffset) {
             writefln("offset of %d greater than stack size %d", offset, aTop);
         }
         return this.aStack[aTop - offset - 1];
@@ -79,6 +78,16 @@ class VM {
         return this.func.chunk.code[this.ip++];
     }
 
+    uint readShort() {
+        ip += 2;
+        uint high = this.func.chunk.code[ip - 2] << 8;
+        uint low = this.func.chunk.code[ip - 1];
+        return high | low;
+
+
+        //return 0;
+    }
+
     bool isNumber(Value value) {
         return value.type == ValueType.NUMBER;
     }
@@ -87,6 +96,10 @@ class VM {
         return value.type == ValueType.STRING;
     }
 
+    bool isBoolean(Value value) {
+        return value.type == ValueType.BOOLEAN;
+    }
+
     double asNumber(Value value) {
         return value.as.number;
     }
@@ -95,9 +108,20 @@ class VM {
         return value.as.str;
     }
 
+    bool asBoolean(Value value) {
+        return value.as.boolean;
+    }
+
+    /*
+    bool isFalsey(Value val) {
+        return isBoolean(val) && val.as.boolean;
+    }
+    */
+
     InterpretResult run() {
-        //int ip = 0;  // TODO this is wrong
+        writeln("== VM running ==");
         while (true) {
+            writeln("          Stacks:");
             write("          A> ");
             for (int i = 0; i < aTop; i++) {
                 writef("[ %s ]", printableValue(aStack[i]));
@@ -130,14 +154,12 @@ class VM {
                     globals[asString(name)] = val;
                     break;
                 case OpCode.OP_GET_GLOBAL:
-                    writeln("in OP_GET_GLOBAL");
                     Value name = func.chunk.constants[readByte()];
                     writefln(asString(name));
                     if (!isString(name)) {
                         writefln("variables must be strings, got %s", printableValue(name));
                         return InterpretResult.RUNTIME_ERROR;  // TODO error
                     }
-                    writefln(asString(name));
                     Value* member = asString(name) in globals;
                     if (member is null) {
                         writefln("no such variable: %s", printableValue(name));
@@ -146,31 +168,17 @@ class VM {
                     pushA(*member);  // do i need to dereference?
                     break;
                 case OpCode.OP_DEF_LOCAL:
-                    //Value name = func.chunk.constants[readByte()];
-                    writefln("in OP_DEF_LOCAL");
-                    //Value val = peekA(0);
                     Value val = popA();
                     pushB(val);
                     break;
-
-
                 case OpCode.OP_GET_LOCAL:
                     ubyte slot = readByte();
-                    writefln("getting local '%d' stackTop '%d'", slot, bTop);
-                    //push(stack[topOffset + slot - 2]);
-                    //push(stack[topOffset + slot]);
-                    pushA(bStack[bTop - slot - 1]);  // NOTE change to bStack
-                    //push(stack[slot]);
+                    pushA(bStack[bTop - slot - 1]);
                     break;
                 case OpCode.OP_SET_LOCAL:
-                    //writeln("in SET_LOCAL");
                     ubyte slot = readByte();
-                    //stack[slot] = peek(0);
-                    bStack[bTop + slot - 1] = peekA(0);  // NOTE change to bStack
-                    popA();  // NOTE changed to bStack
-                    //pop();
-                    //stack[slot] = pop();
-                    writefln("setting local '%d' stackTop '%d'", slot, bTop);
+                    bStack[bTop + slot - 1] = peekA(0);
+                    popA();
                     break;
                case OpCode.OP_CONSTANT:
                     Value constant = this.func.chunk.constants[this.readByte()];
@@ -244,6 +252,22 @@ class VM {
                     popA();  // throw this one away
                     pushA(val);
                     break;
+
+                case OpCode.OP_JUMP:
+                    uint offset = readShort();
+                    ip += offset;
+                    break;
+
+                case OpCode.OP_JUMP_IF_FALSE:
+                    uint offset = readShort();
+                    if (!isBoolean(peekA(0))) {
+                        writeln("if expects a boolean condition");
+                        return InterpretResult.RUNTIME_ERROR; // TODO error
+                    }
+                    if (!asBoolean(peekA(0))) {
+                        ip += offset;
+                    }
+                    break;
                 default:
                     writeln("unknown opcode to run");
                     break;
-- 
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