From dd5210368634e2b322435385eaaaccaa5125b5a9 Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Sun, 24 Oct 2021 15:42:01 +0200
Subject: Add initial IF implementation

---
 src/bytecode/compiler.h | 66 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/bytecode/debug.h    |  3 +++
 src/bytecode/ops.h      |  3 +++
 src/bytecode/vm.h       | 10 ++++++++
 4 files changed, 82 insertions(+)

(limited to 'src')

diff --git a/src/bytecode/compiler.h b/src/bytecode/compiler.h
index b1cdfb9..559ad1c 100755
--- a/src/bytecode/compiler.h
+++ b/src/bytecode/compiler.h
@@ -231,6 +231,71 @@ compile_declare_op(Chunk *chunk, Visitor *vs, Token start, Ops op) {
     add_code(chunk, op, start.line, start.column);
 }
 
+void
+compile_if_op(Chunk *chunk, Visitor *vs, Token start) {
+    Token tok = peek_token(vs);
+    if (tok.type == TOKEN_EOF) {
+        error_push((Error){
+            .type = ERR_TYPE_COMPILER,
+            .value = ERR_UNBALANCED_PAREN,
+            .line = start.line,
+            .col = start.column,
+        });
+        return;
+    }
+    if (tok.type == TOKEN_RPAREN) {
+        error_push((Error){
+            .type = ERR_TYPE_COMPILER,
+            .value = ERR_NOT_ENOUGH_ARGS,
+            .line = start.line,
+            .col = start.column,
+        });
+        return;
+    }
+
+    // Condition.
+    parse_tree(chunk, vs);
+    emit_constant(chunk, tok, FIXNUM_VAL(0xFF));
+    size_t pos = array_size(chunk->code);
+    add_code(chunk, OP_JUMP_IF_FALSE, start.line, start.column);
+
+    // Block true.
+    parse_tree(chunk, vs);
+
+    // No else.
+    if (peek_token(vs).type == TOKEN_RPAREN) {
+        size_t false_block_start = array_size(chunk->code) - pos - 1;
+        size_t num_idx = add_constant(chunk, FIXNUM_VAL(false_block_start));
+        chunk->code[pos - 1] = num_idx;
+        next_token(vs);
+        return;
+    }
+
+    // Else.
+    emit_constant(chunk, tok, FIXNUM_VAL(0xFF));
+    size_t else_pos = array_size(chunk->code);
+    add_code(chunk, OP_JUMP, start.line, start.column);
+
+    size_t false_block_start = array_size(chunk->code) - pos - 1;
+    size_t num_idx = add_constant(chunk, FIXNUM_VAL(false_block_start));
+    chunk->code[pos - 1] = num_idx;
+    parse_tree(chunk, vs);
+    false_block_start = array_size(chunk->code) - else_pos - 1;
+    num_idx = add_constant(chunk, FIXNUM_VAL(false_block_start));
+    chunk->code[else_pos - 1] = num_idx;
+
+    if (peek_token(vs).type != TOKEN_RPAREN) {
+        error_push((Error){
+            .type = ERR_TYPE_COMPILER,
+            .value = ERR_TOO_MANY_ARGS,
+            .line = start.line,
+            .col = start.column,
+        });
+        return;
+    }
+    next_token(vs);
+}
+
 void
 parse_list(Chunk *chunk, Visitor *vs, Token start) {
     if (!has_next_token(vs)) {
@@ -262,6 +327,7 @@ parse_list(Chunk *chunk, Visitor *vs, Token start) {
         case TOKEN_NEWLINE: { compile_list_simple_op(chunk, vs, start, OP_NEWLINE); } break;
         case TOKEN_DEF: { compile_declare_op(chunk, vs, start, OP_DEF); } break;
         case TOKEN_SET: { compile_declare_op(chunk, vs, start, OP_SET); } break;
+        case TOKEN_IF: { compile_if_op(chunk, vs, start); } break;
         default: {
             error_push((Error){
                 .type = ERR_TYPE_COMPILER,
diff --git a/src/bytecode/debug.h b/src/bytecode/debug.h
index 889ae03..674d469 100755
--- a/src/bytecode/debug.h
+++ b/src/bytecode/debug.h
@@ -28,6 +28,9 @@ static const char* ops_str[] = {
     [OP_GREATER] = "OP_GREATER",
     [OP_LESS_EQUAL] = "OP_LESS_EQUAL",
     [OP_GREATER_EQUAL] = "OP_GREATER_EQUAL",
+    // Jump/conditional ops.
+    [OP_JUMP] = "OP_JUMP",
+    [OP_JUMP_IF_FALSE] = "OP_JUMP_IF_FALSE",
     // Display ops.
     [OP_DISPLAY] = "OP_DISPLAY",
     [OP_PRINT] = "OP_PRINT",
diff --git a/src/bytecode/ops.h b/src/bytecode/ops.h
index 50d12fe..5eacaea 100755
--- a/src/bytecode/ops.h
+++ b/src/bytecode/ops.h
@@ -23,6 +23,9 @@ typedef enum Ops {
     OP_GREATER,
     OP_LESS_EQUAL,
     OP_GREATER_EQUAL,
+    // Jump/conditional ops.
+    OP_JUMP,
+    OP_JUMP_IF_FALSE,
     // Display ops.
     OP_DISPLAY,
     OP_PRINT,
diff --git a/src/bytecode/vm.h b/src/bytecode/vm.h
index 51a6f44..b24a5fa 100755
--- a/src/bytecode/vm.h
+++ b/src/bytecode/vm.h
@@ -196,6 +196,16 @@ vm_interpret(VM *vm, Chunk *chunk) {
             case OP_GREATER: { FIXNUM_COMPARE_OP(>); } break;
             case OP_LESS_EQUAL: { FIXNUM_COMPARE_OP(<=); } break;
             case OP_GREATER_EQUAL: { FIXNUM_COMPARE_OP(>=); } break;
+            case OP_JUMP: {
+                ssize_t off = AS_FIXNUM(array_pop(vm->stack));
+                vm->pc += off;
+            } break;
+            case OP_JUMP_IF_FALSE: {
+                ssize_t off = AS_FIXNUM(array_pop(vm->stack));
+                if (IS_FALSE(array_pop(vm->stack))) {
+                    vm->pc += off;
+                }
+            } break;
             case OP_DISPLAY: {
                 display(array_pop(vm->stack));
             } break;
-- 
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