From 629416ffb6e30836f4de4a0f2401ccd66b4ce4a6 Mon Sep 17 00:00:00 2001
From: ubq323 <ubq323@ubq323.website>
Date: Mon, 1 Jul 2024 20:49:14 +0100
Subject: add numeric for form

---
 com.c         | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/for.bth |  2 ++
 tests/for.out | 10 ++++++++++
 3 files changed, 76 insertions(+)
 create mode 100644 tests/for.bth
 create mode 100644 tests/for.out

diff --git a/com.c b/com.c
index 310117a..2c44883 100644
--- a/com.c
+++ b/com.c
@@ -268,6 +268,8 @@ void while_form(Compiler *C, AstVec l, Op _, int flags) {
 	patch(C, ph_b, dest_b - ph_b - 2);
 }
 
+
+
 void arith_form(Compiler *C, AstVec l, Op op, int flags) {
 	compile_node(C, l.vals[1], 0);
 	compile_node(C, l.vals[2], 0);
@@ -339,6 +341,67 @@ void let_form(Compiler *C, AstVec l, Op _, int flags) {
 	end_scope(C);
 }
 
+void for_form(Compiler *C, AstVec l, Op _, int flags) {
+	// (for (x n) ...)
+	CHECK(l.vals[1].ty == AST_LIST, "for needs binding list");
+	AstVec blist = l.vals[1].as.list;
+	CHECK(blist.len == 2, "for binding list must have length 2");
+	CHECK(blist.vals[0].ty == AST_IDENT, "can only bind to ident");
+	char *ivar = blist.vals[0].as.str;
+
+	begin_scope(C);
+
+	compile_opcode(C, OP_LOADK);
+	compile_byte(C, compile_constant(C, VAL_NUM(0)));
+	declare_local(C, ivar);
+	Local *loc = locate_local(C, ivar);
+	int islot = loc->slot;
+
+	compile_node(C, blist.vals[1], 0);
+	declare_local(C, "__max__");
+	loc = locate_local(C, "__max__");
+	int mslot = loc->slot;
+
+	// A
+	// getlocal ivar
+	// getlocal max
+	// cmp
+	// 0branch -> B
+	// body ...
+	// incr ivar
+	// redo -> A
+	// B:
+	// nil
+
+	size_t dest_A = BYTECODE(C).len;
+	compile_opcode(C, OP_GETLOCAL);
+	compile_byte(C, islot);
+	compile_opcode(C, OP_GETLOCAL);
+	compile_byte(C, mslot);
+	compile_opcode(C, OP_CMP);
+	compile_opcode(C, OP_0BRANCH);
+	size_t ph_B = placeholder(C);
+	compile_body(C, l, 2, flags & ~F_tail);
+	compile_opcode(C, OP_DROP);
+	compile_opcode(C, OP_GETLOCAL);
+	compile_byte(C, islot);
+	compile_opcode(C, OP_LOADK);
+	compile_byte(C, compile_constant(C, VAL_NUM(1)));
+	compile_opcode(C, OP_ADD);
+	compile_opcode(C, OP_SETLOCAL);
+	compile_opcode(C, islot);
+	compile_opcode(C, OP_REDO);
+	size_t ph_A = placeholder(C);
+	size_t dest_B = BYTECODE(C).len;
+	compile_opcode(C, OP_NIL);
+
+	patch(C, ph_A , ph_A - dest_A + 2);
+	patch(C, ph_B ,dest_B - ph_B - 2);
+
+	end_scope(C);
+}
+
+
 void def_form(Compiler *C, AstVec l, Op _, int flags) {
 	CHECK(l.vals[1].ty == AST_IDENT, "def's first argument must be ident");
 	CHECK(flags & F_toplevel, "def only allowed at top level");
@@ -395,6 +458,7 @@ static BuiltinForm builtin_forms[] = {
 	{ "do",    1,  true, do_form, 0 },
 	{ "if",    3, false, if_form, 0 },
 	{ "while", 2,  true, while_form, 0 },
+	{ "for",   2,  true, for_form, 0 },
 	{ "fn",    2,  true, fn_form, 0 },
 	{ "let",   2,  true, let_form, 0 },
 	{ "def",   2, false, def_form, 0 },
diff --git a/tests/for.bth b/tests/for.bth
new file mode 100644
index 0000000..4d5f5b1
--- /dev/null
+++ b/tests/for.bth
@@ -0,0 +1,2 @@
+(for (x 10)
+	(say (* x x)))
diff --git a/tests/for.out b/tests/for.out
new file mode 100644
index 0000000..9b81ce7
--- /dev/null
+++ b/tests/for.out
@@ -0,0 +1,10 @@
+0
+1
+4
+9
+16
+25
+36
+49
+64
+81
-- 
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