Standard library, strings, StringView, and regex

This document ties together three related layers: Casprix .cpx modules under lib/, the C runtime used by generated code and embedders, and compiler internals for regex and linear string views.

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1. Casprix standard modules (lib/)

Shipped Casprix sources are rooted at lib/. Typical entry points:

Area	Path	Notes
Core collections / generics	lib/stdlib/Collections.cpx, Generics.cpx, Collections_Simple.cpx	Lists, maps, patterns (evolving)
Interfaces & lambdas	lib/stdlib/Interfaces.cpx, Lambdas.cpx	Shared protocols and helpers
Concurrency	lib/stdlib/Thread.cpx, AsyncThread.cpx	Maps to runtime thread / async APIs
Networking	lib/stdlib/Network.cpx, AsyncNetwork.cpx	HTTP / socket-oriented wrappers
GUI (Skia)	lib/stdlib/GUI.cpx, ModernGUI.cpx	Optional; needs ENABLE_SKIA_GUI build
LLM	lib/llm/	Tokenizer and related .cpx

Imports use quoted paths, e.g. import "lib/stdlib/Collections.cpx" (exact style depends on your project layout).

The stdlib/ directory holds the bootstrap package index and small modules used before the full tree is available; see docs/PROJECT_STRUCTURE.md.

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2. Runtime string API (C)

User-facing string operations for generated code and tests are implemented in C and declared in include/casprix/string_ops.h. The implementation lives in runtime/stdlib/string_ops.c.

Symbols use the historical nuwan_string_* prefix. Capabilities include:

• Concatenation, substring, length
• Case conversion (hot paths may use SIMD-style batching where available)
• Search: index_of, last_index_of, contains, starts_with, ends_with
• Trim variants, split, replace / replace_all
• FNV-1a hash (nuwan_string_hash) and helpers used by the runtime

Unit coverage: tests/runtime/test_stdlib.c.

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3. Linear StringView (compiler semantic layer)

The compiler models a non-owning view into string storage as a linear type: a StringView has move-only semantics and must not outlive its parent string (enforced in semantic analysis, escape analysis, and the drop planner).

Authoritative design notes: src/compiler/sema/linear_view.h.

Practical implications:

• Use-after-move of a StringView is rejected at compile time where tracked.
• Returning or storing a StringView beyond the parent’s scope is rejected when detected.
• Regression / exploratory samples: tests/corpus/stringview_linear.cpx.

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4. Regex → MIR compiler (inside the toolchain)

End-user regex syntax in .cpx is not the focus here; the repository includes a compiler subsystem that compiles a regex pattern into a MIR function that scans a byte buffer in one left-to-right pass (DFA-shaped control flow).

• Implementation: src/compiler/ir/mir_regex.c, API in src/compiler/ir/mir_regex.h.
• Pipeline sketch: parse pattern → NFA (Thompson) → DFA (subset construction) → MIR basic blocks per state + shared reject block.
• Tests: tests/compiler/test_mir_regex.c, corpus integration in tests/compiler/test_mir_corpus_verify.c (includes tests/corpus/cfg_regex_dfa.cpx).

This is primarily for optimization / codegen experiments and corpus verification; wiring every regex surface feature in the language front end is separate work.

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5. Related documentation

• FEATURES.md — compiler capabilities and CLI usage
• PROJECT_STRUCTURE.md — directory map
• CASPRIX_SYNTAX_EBNF.md — grammar reference