Add the MTAccent atom class.

iosMath/lib/MTMathList.h

@@ -210,11 +210,23 @@ typedef NS_ENUM(NSUInteger, MTMathAtomType)
 
 @end
 
+/** An atom with an accent. */
+@interface MTAccent : MTMathAtom
+
+/** Creates a new `MTAccent` with the given value as the accent.
+ */
+- (instancetype)initWithValue:(NSString*) value NS_DESIGNATED_INITIALIZER;
+
+/// The mathlist under the accent.
+@property (nonatomic, nullable) MTMathList* innerList;
+
+@end
+
 /** A representation of a list of math objects.
 
     This list can be constructed directly or built with
     the help of the MTMathListBuilder. It is not required that the mathematics represented make sense
-    (i.e. this cn represent something like "x 2 = +". This list can be used for display using MTLine
+    (i.e. this can represent something like "x 2 = +". This list can be used for display using MTLine
     or can be a list of tokens to be used by a parser after finalizedMathList is called.
  
     @note This class is for ADVANCED usage only.

iosMath/lib/MTMathList.m

@@ -490,6 +490,35 @@ - (id)copyWithZone:(NSZone *)zone
 
 @end
 
+#pragma mark - MTAccent
+
+@implementation MTAccent
+
+- (instancetype)initWithValue:(NSString *)value
+{
+    self = [super initWithType:kMTMathAtomAccent value:value];
+    return self;
+}
+
+- (instancetype)initWithType:(MTMathAtomType)type value:(NSString *)value
+{
+    if (type == kMTMathAtomAccent) {
+        return [self initWithValue:value];
+    }
+    @throw [NSException exceptionWithName:@"InvalidMethod"
+                                   reason:@"[MTAccent initWithType:value:] cannot be called. Use [MTAccent initWithValue:] instead."
+                                 userInfo:nil];
+}
+
+- (id)copyWithZone:(NSZone *)zone
+{
+    MTUnderLine* op = [super copyWithZone:zone];
+    op.innerList = [self.innerList copyWithZone:zone];
+    return op;
+}
+
+@end
+
 #pragma mark - MTMathList
 
 @implementation MTMathList {
@@ -648,6 +677,13 @@ - (MTMathList *)finalized
                 break;
             }
 
+            case kMTMathAtomAccent: {
+                MTAccent* accent = (MTAccent*) atom;
+                MTAccent* newAccent = (MTAccent*) newNode;
+                newAccent.innerList = accent.innerList.finalized;
+                break;
+            }
+
             default:
                 break;
         }

iosMathTests/MTMathListTest.m

@@ -512,4 +512,22 @@ - (void) testCopyUnderline
     [MTMathListTest checkListCopy:copy.innerList original:under.innerList forTest:self];
 }
 
+- (void) testCopyAcccent
+{
+    MTMathList* list = [[MTMathList alloc] init];
+    MTMathAtom* atom = [MTMathAtomFactory placeholder];
+    MTMathAtom* atom2 = [MTMathAtomFactory times];
+    MTMathAtom* atom3 = [MTMathAtomFactory divide];
+    [list addAtom:atom];
+    [list addAtom:atom2];
+    [list addAtom:atom3];
+
+    MTAccent* accent = [[MTAccent alloc] initWithValue:@"^"];
+    XCTAssertEqual(accent.type, kMTMathAtomAccent);
+    accent.innerList = list;
+
+    MTOverLine* copy = [accent copy];
+    [MTMathListTest checkAtomCopy:copy original:accent forTest:self];
+    [MTMathListTest checkListCopy:copy.innerList original:accent.innerList forTest:self];
+}
 @end