Not in BT

Features BT deliberately leaves out, and what to write instead.

Types

Absent	Write instead
User-defined generic types and functions	The built-in parameterized types (array<T>, map<K, V>, ...); interfaces; function values.
Type inference (var, let, auto)	Name the type: int n = 0;.
Unsigned integers other than byte	int or int32, which are signed.
Tuples and multiple return values	Return an object.
Nullable scalars and strings (int?, string?)	A sentinel value, a separate bool, or a wrapper object.
Flow-sensitive null narrowing	Compare with null, then use the value; T? stays T?.
Type aliases	—

Declarations

Absent	Write instead
Constructors and destructors	A factory function returning an object literal; explicit close methods.
Inheritance, abstract classes, implements	Interfaces (structural) and composition.
Static members	Top-level functions, constants and variables.
Method overloading and function overloading	Distinct names.
Default, optional and variadic parameters	Named arguments with explicit values; an array parameter.
Operator overloading	Methods.
Nested or local functions	Top-level functions.
Access modifiers other than ~	~ (package-private declaration or field); everything else is public to files that include the package.
Attributes, annotations, decorators (@)	—
Preprocessor and macros	—

Expressions and operators

Absent	Write instead
Lambdas, closures, anonymous functions	Top-level functions as values; pass context as parameters or object fields.
Bound method values (obj.method as a value)	A top-level function taking the receiver.
Ternary c ? a : b	A switch expression, or if/else assigning a local.
Bitwise and shift operators (&, |, ^, <<, >>, unary ~)	Arithmetic (*, /, %).
Prefix ++x; ++/-- as expressions	x++; as a statement.
printf-style formatting (width, padding, precision)	Interpolation ("hp ${hp}") and float_to_string(x, decimals).
Indexing or slicing strings with []	string methods (byte_at, slice, chars).
Hexadecimal, octal, binary literals; digit separators	Decimal literals.
Map literals typed by their destination	A map literal takes its types from its first entry; write entries of the right type, or use new and assignment.
Empty [] and {} literals	new array<T>(), new map<K, V>().
Reflection beyond typeof(T) (field enumeration, type names, dynamic invocation)	—

Statements and control flow

Absent	Write instead
do ... while	for { ...; if (!cond) { break; } }.
Labeled break/continue, goto	Flags, or move the inner loop into a function and return.
try / catch / finally	!! { } handlers and && { } deferred blocks.
Throwing non-error values	throw new error(code, message);.
Empty statement ;	{ }.

Collections

Absent	Write instead
Map deletion	Store a nullable value or a tombstone flag.
Iterating channels or buffers with for ... in	receive() loops; index loops over a buffer.

Concurrency

Absent	Write instead
async / await keywords	Every call may wait; branch and join make concurrency explicit.
select send arms	A helper task that does the send.
Threads, atomics and condition variables	Tasks, channels and Mutex.
Thread-local storage	Pass state explicitly.

Runtime

Absent	Note
Manual memory management, pointers	Memory is freed automatically.
Finalizers	Explicit close; && { } cleanup.
Changing a running program in place	The host recompiles and restarts the program.
Catching traps	Traps end the task; validate before dividing or indexing.

See also

• Lexical structure, Types, Expressions, Statements
• Guide: Syntax reference