Merge branch 'develop': eliminate duplicated prefixMode state

Task be: prefixMode now lives in Operations only. RPN delegates
GetPrefixMode/SetPrefixMode through the Operator interface.
Removed direct r.prefixMode writes from evaluate().

3 files changed, 5 insertions, 10 deletions

diff --git a/internal/rpn/operations.go b/internal/rpn/operations.go
index 04c2014..d45ffd1 100644
--- a/internal/rpn/operations.go
+++ b/internal/rpn/operations.go
@@ -158,6 +158,8 @@ type Operator interface {
 	SetMode(CalculationMode)
 	// SetPrefixMode sets the prefix mode for data size calculations
 	SetPrefixMode(PrefixMode)
+	// GetPrefixMode returns the current prefix mode
+	GetPrefixMode() PrefixMode
 	// Metric command handlers
 	MetricShow(stack *Stack) (string, error)
 	MetricList(stack *Stack) (string, error)
diff --git a/internal/rpn/rpn_parse.go b/internal/rpn/rpn_parse.go
index 7abd41c..ab64ec7 100644
--- a/internal/rpn/rpn_parse.go
+++ b/internal/rpn/rpn_parse.go
@@ -367,17 +367,12 @@ func (r *RPN) evaluate(input string, tokens []string) (string, error) {
 				return result, nil
 			case "binary":
 				if i+2 < len(tokens) && tokens[i+2] == "set" {
-					// Lock order: r.mu → o.mu (same as RPN.SetPrefixMode)
-					// No deadlock risk: both paths acquire in the same direction.
-					// r.mu is held by evaluate(); o.mu is a separate mutex on Operations.
-					r.prefixMode = IEC
 					r.ops.SetPrefixMode(IEC)
 					return "prefix mode: IEC", nil
 				}
 				return "", fmt.Errorf("rpn: metric binary: use 'metric binary set'")
 			case "decimal":
 				if i+2 < len(tokens) && tokens[i+2] == "set" {
-					r.prefixMode = SI
 					r.ops.SetPrefixMode(SI)
 					return "prefix mode: SI", nil
 				}
diff --git a/internal/rpn/rpn_state.go b/internal/rpn/rpn_state.go
index 3b63984..a146409 100644
--- a/internal/rpn/rpn_state.go
+++ b/internal/rpn/rpn_state.go
@@ -20,7 +20,6 @@ type RPN struct {
 	maxStack      int
 	currentStack  *Stack
 	mode          CalculationMode
-	prefixMode    PrefixMode
 }
 
 // NewRPN creates a new RPN parser and evaluator with the given variable store.
@@ -37,7 +36,6 @@ func NewRPN(vars VariableStore) *RPN {
 		maxStack:      1000, // Reasonable limit for RPN expressions
 		currentStack:  NewStack(),
 		mode:          FloatMode, // Default mode
-		prefixMode:    SI,        // Default prefix mode
 	}
 }
 
@@ -96,19 +94,19 @@ func (r *RPN) Stack() []Number {
 }
 
 // SetPrefixMode sets the prefix mode (SI or IEC).
-// Propagates to the Operations instance so arithmetic uses the correct mode.
+// Delegates to the Operations instance.
 // This method is thread-safe for writes.
 func (r *RPN) SetPrefixMode(mode PrefixMode) {
 	r.mu.Lock()
 	defer r.mu.Unlock()
-	r.prefixMode = mode
 	r.ops.SetPrefixMode(mode)
 }
 
 // GetPrefixMode returns the current prefix mode.
+// Delegates to the Operations instance.
 // This method is thread-safe for concurrent reads.
 func (r *RPN) GetPrefixMode() PrefixMode {
 	r.mu.RLock()
 	defer r.mu.RUnlock()
-	return r.prefixMode
+	return r.ops.GetPrefixMode()
 }