works

rust2/src/naive_interpreter.rs

@@ -0,0 +1,55 @@
+use crate::parse::Instr;
+use std::io::{Read, Write};
+use std::num::Wrapping;
+
+const MEM_SIZE: usize = 32_000;
+
+type Memory = [Wrapping<u8>; MEM_SIZE];
+
+pub fn run(instrs: &[Instr<'_>]) {
+    let mut mem = [Wrapping(0u8); MEM_SIZE];
+    let mut ptr = 0;
+
+    execute(&mut mem, &mut ptr, instrs);
+}
+
+fn execute(mem: &mut Memory, ptr: &mut usize, instrs: &[Instr<'_>]) {
+    for instr in instrs {
+        match instr {
+            Instr::Add => {
+                mem[*ptr] += 1;
+            }
+            Instr::Sub => {
+                mem[*ptr] -= 1;
+            }
+            Instr::Right => {
+                *ptr += 1;
+                if *ptr >= MEM_SIZE {
+                    *ptr = 0;
+                }
+            }
+            Instr::Left => {
+                if *ptr == 0 {
+                    *ptr = MEM_SIZE - 1;
+                } else {
+                    *ptr -= 1;
+                }
+            }
+            Instr::Out => {
+                let char = mem[*ptr].0 as char;
+                print!("{char}",);
+                std::io::stdout().flush().unwrap();
+            }
+            Instr::In => {
+                let mut buf = [0; 1];
+                std::io::stdin().read_exact(&mut buf).unwrap();
+                mem[*ptr] = Wrapping(buf[0]);
+            }
+            Instr::Loop(body) => {
+                while mem[*ptr] != Wrapping(0) {
+                    execute(mem, ptr, body);
+                }
+            }
+        }
+    }
+}