chain word and better save/load UI

crates/forth/src/ops.rs

@@ -79,4 +79,5 @@ pub enum Op {
     Ramp,
     Range,
     Noise,
+    Chain,
 }

crates/forth/src/types.rs

@@ -19,6 +19,7 @@ pub struct ExecutionTrace {
 pub struct StepContext {
     pub step: usize,
     pub beat: f64,
+    pub bank: usize,
     pub pattern: usize,
     pub tempo: f64,
     pub phase: f64,

crates/forth/src/vm.rs

@@ -299,6 +299,7 @@ impl Forth {
                     let val = match name.as_str() {
                         "step" => Value::Int(ctx.step as i64, None),
                         "beat" => Value::Float(ctx.beat, None),
+                        "bank" => Value::Int(ctx.bank as i64, None),
                         "pattern" => Value::Int(ctx.pattern as i64, None),
                         "tempo" => Value::Float(ctx.tempo, None),
                         "phase" => Value::Float(ctx.phase, None),
@@ -628,6 +629,24 @@ impl Forth {
                         .insert("__tempo__".to_string(), Value::Float(clamped, None));
                 }
 
+                Op::Chain => {
+                    let pattern = stack.pop().ok_or("stack underflow")?.as_int()? - 1;
+                    let bank = stack.pop().ok_or("stack underflow")?.as_int()? - 1;
+                    if bank < 0 || pattern < 0 {
+                        return Err("chain: bank and pattern must be >= 1".into());
+                    }
+                    if bank as usize == ctx.bank && pattern as usize == ctx.pattern {
+                        // chaining to self is a no-op
+                    } else {
+                        let key = format!("__chain_{}_{}__", ctx.bank, ctx.pattern);
+                        let val = format!("{bank}:{pattern}");
+                        self.vars
+                            .lock()
+                            .unwrap()
+                            .insert(key, Value::Str(val, None));
+                    }
+                }
+
                 Op::ListStart => {
                     stack.push(Value::Marker);
                 }

crates/forth/src/words.rs

@@ -428,6 +428,13 @@ pub const WORDS: &[Word] = &[
         example: "pattern => 0",
         compile: Context("pattern"),
     },
+    Word {
+        name: "pbank",
+        stack: "(-- n)",
+        desc: "Current pattern's bank index",
+        example: "pbank => 0",
+        compile: Context("bank"),
+    },
     Word {
         name: "tempo",
         stack: "(-- f)",
@@ -621,6 +628,13 @@ pub const WORDS: &[Word] = &[
         example: "140 tempo!",
         compile: Simple,
     },
+    Word {
+        name: "chain",
+        stack: "(bank pattern --)",
+        desc: "Chain to bank/pattern (1-indexed) when current pattern ends",
+        example: "1 4 chain",
+        compile: Simple,
+    },
     // Lists
     Word {
         name: "[",
@@ -1550,6 +1564,7 @@ pub(super) fn simple_op(name: &str) -> Option<Op> {
         "ramp" => Op::Ramp,
         "range" => Op::Range,
         "noise" => Op::Noise,
+        "chain" => Op::Chain,
         _ => return None,
     })
 }