Surface map · fx docs

Package 0.9.74 — complete inventory of shipped functionality. If it is not listed here, do not assume it exists. Includes typed Id, lexical loans, no-grow v[i]=x, concurrency facades, SIMD / @override, and a full std/ module list.

Prefer the language tour when learning. Prefer this page when asking "does fx have X?" Package markdown: docs/SURFACE.md.

A. Kernel

Keywords

enum struct extern fn import let match module return effects if while for break continue else defer region arena scope temp fx own mut true false using · Ok / Err

Comments: //. Refinement where is verification-tier only.

Types

Kind	Forms
Integers	`i8` `i16` `i32` `i64` · `u8`…`u64`
Floats	`f32` `f64`
Scalars	`bool` `string` `void` `core_Err`
User types	`struct` · `enum` (unit + payload)
Collections	`Vec<T>` · `[T; N]` · `&[T]` · `&mut [T]` · `StrBuilder` · `Map<string, i32>` · `Map<string, string>` · `Buf` / `Bytes`
Sum / ownership	`Result<T, E>` · `own` · `&` · `&mut` · `&region`
SIMD	`v4i32` · `v4f32` · `v16u8` (portable foothold)
Generics	type params on fn/struct · no traits

Control · operators · Result

if / while / C-style for / match / defer / break / continue
Index: arrays R/W; &[T] read-only; &mut [T] write-through; Vec reads via v[i] / vec_get; no-grow slot writes via v[i]=x / vec_set under mut
Sub-slice: a[lo..hi] → &[T] (exclusive hi)
Record update: p with { y: 32 }
Ok / Err / ? · no Option

B. Memory model

Effects: alloc · mut · io (signature-visible)
Regions: arena · temp · scope · fx — see Regions
Growers are value-threaded: reassign v = vec_push(v, x) (same for map / strbuf / buf)
Lexical loans: shared XOR mut on & / &mut; region escape FX0015; borrow conflict FX0019; no lifetime parameters

C. Data (limits inline)

Surface	Can	Cannot / limit
`Vec<T>`	push/get/len; read `v[i]`; no-grow `v[i]=x` / `vec_set`	growable index assign that reallocates; many exotic element types
`&[T]`	read; sub-slice	write through immutable view
`&mut [T]`	index write-through (array-backed)	`&mut Vec` as slice; mut sub-slices
`Map<string, i32>`	CRUD + `map_nth_*` + `map_add_i32`	insertion-order iterate
Pool / `Id`	`std/pool` typed handles; `set` → `vec_set`	bare `i32` at get/set
`Map<string, string>`	`map_new_ss` / shared map builtins	other KV shapes
`Buf` / `Bytes`	grow + view helpers	general streaming I/O API

D. `std/`

Core: vec · string · map · set · buf · box · pair · math · fmt · io · queue · pool · fx_defaults

Caps / net: cap · guest · io_cap · net (TCP dial under NetCap; dial_tls always fails in this package)

Concurrency (link host/concur): nursery · chan · select · mailbox · supervise · sync · async (deprecated stub)

Also: path · strutil · encoding · fs · fs_walk · log · json · json_validate · json_full · sqlite · http · time · env · testing · proptest

Details: Standard library · package docs/SURFACE.md §D.

D2–D4. Loans · SIMD · asm

Lexical loans — shared XOR mut · region escape · Hylo call-end · no loan { } sugar
SIMD — v4i32 / v4f32 / v16u8 + helpers; scalar emit-C SoT; optional SSE/NEON
@override / asm { } — portable fx body remains SoT; constrained clobber checks

E. Tooling

doctor · version · new · check · run / build · emit-c · surface · test / fuzz · cc · lsp · mcp · locate · bind · mod vendor|tidy|verify

Useful flags: --cli · --host · --guest · --driver auto|sh|foundry · --fallback-emit-c · --link. Prebuilt: Windows + Linux x86_64. See CLI.

F. Interop

Native-first Auto fx run (the primary compiler path when supported; built-in fallback otherwise) · IR → native when QBE staged · --emit-c first-class
--cli / --host for C main · --use native lib units · link-args helpers
TCP under NetCap; HTTPS via separate fxfetch tool (not in-package TLS)
Non-C FFI not shipped · Wrap

G. Limits (0.9.74)

Also shipped: collection sugar v.push / m.insert; lexical loans; SIMD foothold; @override / constrained asm; guest vec_filter / vec_map / vec_collect; structured concurrency facades; module passport via fx surface.

Not claimed: traits, closures, iterators, Option; nested/exotic Vec shapes; growable v[i]=x that reallocates; package registry; language-package TLS dial (dial_tls always fails; use fxfetch); lexer keywords nursery/spawn/await; macOS prebuilt; fx run program-argv passthrough; DAP mega-IDE; language-wide formal certification; calling this v1.0.

Quick "can I build X?"

Goal	Path
Hello + visible heap	`fx new hello` → `fx run`
Grow collections	value-thread vec / map / buf / strbuf
Vec slot write	`vec_set` / no-grow `v[i]=x` · `examples/pattern_pool`
Shared XOR mut / loans	`&` / `&mut` · Regions
Tally / accumulate	`map_add_i32` · `examples/composition_tally`
Graph / reachability	typed `Id` pool · `examples/composition_reach`
TCP dial	`std/net.dial` under NetCap
HTTPS GET	separate fxfetch tool
Structured concurrency	`std/nursery` + `host/concur`
Embed in C	`--cli` / `--host`
Inspect lowering	`fx emit-c` · `fx surface`

Start · Language · Reference · Std · llms.txt

fx surface map (as implemented)