Unsupported features
This page lists important limits of the currently implemented language,
runtime, and target. Planned work is tracked in the
project roadmap; an unchecked roadmap item is not part of
the supported language.
Language limitations
nes_color, byte, and boolean are the only built-in types.type declarations and user-defined types are not supported.- Constants cannot refer to other constants, and constant initializers cannot
contain expressions.
- Type inference and implicit conversions are not supported.
- Arithmetic is limited to
byte operands with unary + and -, binary +
and -, and parentheses.
- Multiplication and division are not supported.
- Equality and inequality require matching types; ordered comparisons are
limited to
byte.
- Boolean expressions support only
not, and, and or.
case, arrays, records, functions, runtime strings, and inline Assembly are
not supported.- Procedure parameters are limited to
byte and boolean values. There are
no reference parameters, default values, return values, or general local
variables.
- Procedure calls may be nested but cannot be recursive.
- Dynamic memory and object orientation are not supported.
Statement and execution limitations
- Statements are limited to assignment,
inc and dec, if/else,
supported loops, break, continue, procedure calls,
nes.set_background_color, and nes.run.
- Conditional branches and loop bodies may contain supported statements, but
NES runtime commands remain top-level only.
while, repeat/until, and for loops execute only during initialization
before nes.run; they are not frame-based gameplay loops.for supports only byte control variables and bounds. A control variable
cannot be modified inside its loop body.
Runtime and target limitations
- Variables use regular CPU RAM; zero-page allocation is not implemented.
- Only NTSC NES, mapper 0, 32 KiB PRG-ROM, and 8 KiB CHR-ROM are supported.
- CHR-ROM is empty.
- Sprites, controller input, audio, graphics assets, and frame callbacks are
not supported.
- The compiler does not provide a game engine or a general optimization pass.