nes-pascal

Unsupported features

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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, boolean, sprite, and metasprite are the built-in types. User-defined type declarations support nominal enumerations and fixed-layout records.
• 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; enums support only those two comparisons. Ordered comparisons are limited to byte.
• Boolean expressions support only not, and, and or.
• case, runtime strings, and inline Assembly are not supported. User functions return only byte or boolean and use only byte/boolean value parameters. Arrays are limited to fixed-size, one-dimensional global arrays of byte, boolean, or records; arrays of enum are not supported. Records are limited to named static layouts with byte, boolean, or enum fields; nested, anonymous, recursive, variant, packed, and whole-record operations are not supported. A small fixed set of built-in query expressions and the statically resolved nes.sprite_create() and nes.metasprite_create(frame) intrinsics are supported.
• Procedure and function parameters are limited to byte and boolean values; enum parameters are not yet supported. There are no reference parameters, default values, aggregate return values, or general local variables.
• Procedure and function calls may be nested. Direct, indirect, and mixed recursion is not supported.
• 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, the palette APIs, nes.load_background, nes.set_background_color, nes.set_scroll, the nes.sprite_* hardware sprite primitives, compile-time nes.import_metasprite, and the nes.metasprite_* primitives, nes.run, nes.wait_frame, nes.on_update, nes.on_vblank, and the fixed controller-example nes.set_sprite_zero helper.
• Conditional branches and loop bodies may contain supported statements, but nes.run and callback registration remain top-level only. Palette calls in runtime control flow or procedures are staged for VBlank.
• Frame-synchronized loops and update callbacks run on the main thread. NMI may invoke only one statically registered, transitively validated VBlank callback.
• for supports only byte control variables and bounds. A control variable cannot be modified inside its loop body.

Runtime and target limitations

• Automatic Zero Page promotion is limited to the deterministic global-variable policy. Explicit Zero Page declarations are not implemented.
• Only NTSC NES, mapper 0, 32 KiB PRG-ROM, and 8 KiB CHR-ROM are supported.
• One raw, exactly 8 KiB CHR-ROM file is supported. CHR-RAM, multiple files or banks, graphics conversion, compression, and runtime CHR updates are not.
• One raw 1 KiB nametable for nametable 0 is supported during initialization, either combined or as 960 tile bytes plus 64 attribute bytes, followed by at most four queued tile or raw attribute-byte updates per frame. Multiple screens, generated nametables, alternate nametable selection, scrolling gameplay systems, and streaming are not supported. One fixed scroll pair can be staged with nes.set_scroll.
• Standard controllers 1 and 2 are supported without remapping, Four Score, expansion devices, buffering, combos, turbo, or DMC-safe repeated reads.
• Hardware sprite primitives support all 64 OAM entries, individual fields, palette/flip/priority attributes, deterministic hide/show, static individual allocation, and NMI OAM DMA. Metasprites support statically owned arbitrary component layouts, manual frame selection, whole-object position, visibility, flip, hardware-sprite clipping, and automatic looping or one-shot frame sequences. Runtime creation/destruction, variable playback speed, animation blending, automatic collision attachment, sprite multiplexing/flickering, sorting, and scanline-overflow mitigation are not supported. Explicit collision helpers are available separately. nes.set_sprite_zero remains a legacy compatibility helper.
• Callback registration is static. There is only one callback of each kind, with no parameters, return values, priorities, lists, removal, indirect calls, IRQ callbacks, or user-owned interrupt handlers.
• There is no generic PPU command queue. Runtime palette changes use one fixed shadow and bounded VBlank uploader; other rendering-time PPU writes remain unsupported.
• The compiler does not provide a game engine or a general optimization pass; Zero Page promotion is a fixed allocation policy, not a hotness optimizer.

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