refactor: remove unused StackOperations struct

This struct provided stack manipulation operator implementations but was
never used in the codebase. All stack operations are implemented directly
in the Operations struct in operations.go.

1 files changed, 0 insertions, 68 deletions

diff --git a/internal/rpn/stack.go b/internal/rpn/stack.go
deleted file mode 100644
index a956902..0000000
--- a/internal/rpn/stack.go
+++ /dev/null
@@ -1,68 +0,0 @@
-// SPDX-License-Identifier: MIT
-// Copyright (c) 2026 Paul Buetow
-
-package rpn
-
-import (
-	"fmt"
-)
-
-// StackOperations provides stack manipulation operator implementations.
-type StackOperations struct {
-}
-
-// NewStackOperations creates a new StackOperations instance.
-func NewStackOperations() *StackOperations {
-	return &StackOperations{}
-}
-
-// Dup duplicates the top stack value.
-func (o *StackOperations) Dup(stack *Stack) error {
-	val, err := stack.Peek()
-	if err != nil {
-		return fmt.Errorf("insufficient operands for dup: %w", err)
-	}
-	stack.Push(val)
-	return nil
-}
-
-// Swap swaps the top two stack values.
-func (o *StackOperations) Swap(stack *Stack) error {
-	b, err := stack.Pop()
-	if err != nil {
-		return fmt.Errorf("insufficient operands for swap: %w", err)
-	}
-
-	a, err := stack.Pop()
-	if err != nil {
-		return fmt.Errorf("insufficient operands for swap: %w", err)
-	}
-
-	// Push in swapped order
-	stack.Push(b)
-	stack.Push(a)
-	return nil
-}
-
-// Pop removes the top stack value.
-func (o *StackOperations) Pop(stack *Stack) error {
-	_, err := stack.Pop()
-	if err != nil {
-		return fmt.Errorf("insufficient operands for pop: %w", err)
-	}
-	return nil
-}
-
-// Show returns the current stack state as a string without modifying it.
-func (o *StackOperations) Show(stack *Stack) (string, error) {
-	if stack.Len() == 0 {
-		return "", fmt.Errorf("empty stack")
-	}
-	// For now, just return the top value as a string
-	// In a full implementation, this would show the entire stack
-	val, err := stack.Peek()
-	if err != nil {
-		return "", err
-	}
-	return val.String(), nil
-}