From b94723f1baf8e3096681489ff2a2d7e4eb81900a Mon Sep 17 00:00:00 2001
From: Michael Sippel <micha@fragmental.art>
Date: Sun, 5 May 2024 18:16:22 +0200
Subject: [PATCH] assembler: add while_loop

---
 src/assembler.rs | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/assembler.rs b/src/assembler.rs
index d03d58f..e927e74 100644
--- a/src/assembler.rs
+++ b/src/assembler.rs
@@ -42,8 +42,26 @@ impl Assembler {
         self
     }
 
+    pub fn while_loop(mut self, mut condition: Assembler, mut body: Assembler) -> Assembler {
+        let cond_len = condition.instructions.len();
+        let body_len = body.instructions.len();
+        self.instructions.append( &mut condition.instructions );
+
+        // jump to end
+        self.instructions.push( VM_Instruction::Branch as VM_Word );
+        self.instructions.push( body_len as VM_Word + 2 );
+
+        self.instructions.append( &mut body.instructions );
+
+        // jump back to condition
+        self.instructions.push( VM_Instruction::Jmp as VM_Word );
+        self.instructions.push( -2-(body_len as VM_Word)-2-(cond_len as VM_Word) ); 
+
+        self
+    }
+
     pub fn branch(mut self, mut if_branch: Assembler, mut else_branch: Assembler) -> Assembler {
-        self.instructions.push(VM_Instruction::Branch as VM_Word );
+        self.instructions.push(VM_Instruction::Branch as VM_Word);
         self.instructions.push( if_branch.instructions.len() as VM_Word + 2);
 
         self.instructions.append( &mut if_branch.instructions );