From 0a80344c07e39ed9c7c5bca9e5f17e5b8612c4bc Mon Sep 17 00:00:00 2001
From: Yui <yui300127@gmail.com>
Date: Sat, 29 Nov 2025 23:08:50 +0300
Subject: [PATCH] Add C-style for loops

---
 docs/bext.md     | 13 +++++++++++
 src/b.rs         | 58 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/lexer.rs     |  3 +++
 tests.json       | 56 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/for_loop.b | 27 ++++++++++++++++++++++
 5 files changed, 157 insertions(+)
 create mode 100644 tests/for_loop.b

diff --git a/docs/bext.md b/docs/bext.md
index b2993251..75e77308 100644
--- a/docs/bext.md
+++ b/docs/bext.md
@@ -56,6 +56,19 @@ Some targets like `gas-aarch64-darwin` have a different calling convention for v
 this is needed to make the compiler use the correct calling convention. \
 the syntax is `__variadic__(function_name, number_of_fixed_args);`
 
+## C-style for loops
+```c
+main() {
+    for (auto i = 2; i < 5; i++) {
+      printf("%lld^2 = %lld\n", i, i*i);
+    }
+
+    for(;;) printf("infinite loop\n");
+}
+```
+
+Very useful for iterating over a range of numbers.
+
 <!--
     TODO: hex-literals and C++ style comments are currently considered deviations
     and not extensions, thus disabled in historical mode, which is a bug.
diff --git a/src/b.rs b/src/b.rs
index 0193e3da..feb3c3fc 100644
--- a/src/b.rs
+++ b/src/b.rs
@@ -789,6 +789,64 @@ pub unsafe fn compile_statement(l: *mut Lexer, c: *mut Compiler) -> Option<()> {
             push_opcode(Op::Label {label: out_label}, (*l).loc, c);
             Some(())
         }
+        Token::For => {
+            scope_push(&mut (*c).vars);
+            get_and_expect_token(l, Token::OParen)?;
+
+            let cond_label = allocate_label_index(c);
+            let iter_label = allocate_label_index(c);
+            let body_label = allocate_label_index(c);
+            let out_label = allocate_label_index(c);
+
+            let saved_point = (*l).parse_point;
+            lexer::get_token(l)?;
+
+            if (*l).token == Token::Auto {
+                get_and_expect_token(l, Token::ID)?;
+                let name = arena::strdup(&mut (*c).arena, (*l).string);
+                let index = allocate_auto_var(&mut (*c).auto_vars_ator);
+                declare_var(c, name, (*l).loc, Storage::Auto {index})?;
+                get_and_expect_token(l, Token::Eq)?;
+                let loc = (*l).loc;
+                let (arg, _) = compile_expression(l, c)?;
+                push_opcode(Op::AutoAssign {index, arg}, loc, c);
+                get_and_expect_token(l, Token::SemiColon)?;
+            } else if (*l).token != Token::SemiColon {
+                (*l).parse_point = saved_point;
+                compile_expression(l, c)?;
+                get_and_expect_token(l, Token::SemiColon)?;
+            }
+
+            push_opcode(Op::Label {label: cond_label}, (*l).loc, c);
+                let saved_point = (*l).parse_point;
+                lexer::get_token(l);
+                if (*l).token != Token::SemiColon {
+                    (*l).parse_point = saved_point;
+                    let (arg, _) = compile_expression(l, c)?;
+                    push_opcode(Op::JmpIfNotLabel{label: out_label, arg}, (*l).loc, c);
+                    get_and_expect_token(l, Token::SemiColon)?;
+                }
+            push_opcode(Op::JmpLabel{label: body_label}, (*l).loc, c);
+
+            push_opcode(Op::Label {label: iter_label}, (*l).loc, c);
+                let saved_point = (*l).parse_point;
+                lexer::get_token(l);
+                if (*l).token != Token::CParen {
+                    (*l).parse_point = saved_point;
+                    compile_expression(l, c)?;
+                    get_and_expect_token(l, Token::CParen)?;
+                }
+            push_opcode(Op::JmpLabel{label: cond_label}, (*l).loc, c);
+
+
+            push_opcode(Op::Label {label: body_label}, (*l).loc, c);
+                compile_statement(l, c)?;
+            push_opcode(Op::JmpLabel{label: iter_label}, (*l).loc, c);
+            push_opcode(Op::Label {label: out_label}, (*l).loc, c);
+
+            scope_pop(&mut (*c).vars);
+            Some(())
+        }
         Token::Return => {
             get_and_expect_tokens(l, &[Token::SemiColon, Token::OParen])?;
             if (*l).token == Token::SemiColon {
diff --git a/src/lexer.rs b/src/lexer.rs
index 926d6472..3b773385 100644
--- a/src/lexer.rs
+++ b/src/lexer.rs
@@ -88,6 +88,7 @@ pub enum Token {
     If,
     Else,
     While,
+    For,
     Switch,
     Goto,
     Return,
@@ -153,6 +154,7 @@ pub unsafe fn display_token(token: Token) -> *const c_char {
         Token::If         => c!("keyword `if`"),
         Token::Else       => c!("keyword `else`"),
         Token::While      => c!("keyword `while`"),
+        Token::For        => c!("keyword `for`"),
         Token::Switch     => c!("keyword `switch`"),
         Token::Goto       => c!("keyword `goto`"),
         Token::Return     => c!("keyword `return`"),
@@ -259,6 +261,7 @@ const KEYWORDS: *const [(*const c_char, Token)] = &[
     (c!("if"), Token::If),
     (c!("else"), Token::Else),
     (c!("while"), Token::While),
+    (c!("for"), Token::For),
     (c!("switch"), Token::Switch),
     (c!("goto"), Token::Goto),
     (c!("return"), Token::Return),
diff --git a/tests.json b/tests.json
index d14d5748..1215e446 100644
--- a/tests.json
+++ b/tests.json
@@ -2147,5 +2147,61 @@
         "expected_stdout": "",
         "state": "Disabled",
         "comment": "Doesn't make sense for this target"
+    },
+    {
+        "case": "for_loop",
+        "target": "ilasm-mono",
+        "expected_stdout": "",
+        "state": "Enabled",
+        "comment": "Failed to build on record"
+    },
+    {
+        "case": "for_loop",
+        "target": "gas-aarch64-linux",
+        "expected_stdout": "i: 0\ni: 1\ni: 2\ni outside: 69\nj: 3\nj: 5\nj: 7\nx: 2\nx: 4\nx: 8\ny: 69\ny: 70\ny: 71\nz: 100\nz: 101\nz: 102\noh no!\n",
+        "state": "Enabled",
+        "comment": ""
+    },
+    {
+        "case": "for_loop",
+        "target": "gas-aarch64-darwin",
+        "expected_stdout": "i: 0\ni: 1\ni: 2\ni outside: 69\nj: 3\nj: 5\nj: 7\nx: 2\nx: 4\nx: 8\ny: 69\ny: 70\ny: 71\nz: 100\nz: 101\nz: 102\noh no!\n",
+        "state": "Enabled",
+        "comment": ""
+    },
+    {
+        "case": "for_loop",
+        "target": "gas-x86_64-linux",
+        "expected_stdout": "i: 0\ni: 1\ni: 2\ni outside: 69\nj: 3\nj: 5\nj: 7\nx: 2\nx: 4\nx: 8\ny: 69\ny: 70\ny: 71\nz: 100\nz: 101\nz: 102\noh no!\n",
+        "state": "Enabled",
+        "comment": ""
+    },
+    {
+        "case": "for_loop",
+        "target": "gas-x86_64-windows",
+        "expected_stdout": "i: 0\r\ni: 1\r\ni: 2\r\ni outside: 69\r\nj: 3\r\nj: 5\r\nj: 7\r\nx: 2\r\nx: 4\r\nx: 8\r\ny: 69\r\ny: 70\r\ny: 71\r\nz: 100\r\nz: 101\r\nz: 102\r\noh no!\r\n",
+        "state": "Enabled",
+        "comment": ""
+    },
+    {
+        "case": "for_loop",
+        "target": "gas-x86_64-darwin",
+        "expected_stdout": "i: 0\ni: 1\ni: 2\ni outside: 69\nj: 3\nj: 5\nj: 7\nx: 2\nx: 4\nx: 8\ny: 69\ny: 70\ny: 71\nz: 100\nz: 101\nz: 102\noh no!\n",
+        "state": "Enabled",
+        "comment": ""
+    },
+    {
+        "case": "for_loop",
+        "target": "6502-posix",
+        "expected_stdout": "i: 0\r\ni: 1\r\ni: 2\r\ni outside: 69\r\nj: 3\r\nj: 5\r\nj: 7\r\nx: 2\r\nx: 4\r\nx: 8\r\ny: 69\r\ny: 70\r\ny: 71\r\nz: 100\r\nz: 101\r\nz: 102\r\noh no!\r\n",
+        "state": "Enabled",
+        "comment": ""
+    },
+    {
+        "case": "for_loop",
+        "target": "uxn",
+        "expected_stdout": "i: 0\ni: 1\ni: 2\ni outside: 69\nj: 3\nj: 5\nj: 7\nx: 2\nx: 4\nx: 8\ny: 69\ny: 70\ny: 71\nz: 100\nz: 101\nz: 102\noh no!\n",
+        "state": "Enabled",
+        "comment": ""
     }
 ]
diff --git a/tests/for_loop.b b/tests/for_loop.b
new file mode 100644
index 00000000..9d36effe
--- /dev/null
+++ b/tests/for_loop.b
@@ -0,0 +1,27 @@
+main() {
+  auto i; i = 69;
+  for (auto i = 0; i < 3; i++) printf("i: %lld\n", i);
+  printf("i outside: %lld\n", i);
+
+  auto j;
+  for (j = 3; j < 9; j += 2) printf("j: %lld\n", j);
+
+  auto x; x = 2;
+  for (;x < 10; x *= 2) printf("x: %lld\n", x);
+
+  auto y; y = 69;
+  for (;y <= 71;) printf("y: %lld\n", y++);
+
+  auto z; z = 100;
+  for (;;z++) {
+    printf("z: %lld\n", z);
+    if (z >= 102) goto out1;
+  }
+  out1:
+
+  for(;;) {
+    printf("oh no!\n");
+    goto out2;
+  }
+  out2:
+}