Flecha built-in and library API style

These rules govern APIs supplied to Flecha programs by the language and its libraries: primitive members, compiler built-ins, the runtime-facing prelude, and the future standard library. They do not govern ordinary user-defined Flecha functions, and they do not replace the C++ implementation rules in CODE_STYLE.md.

For Flecha source formatting in std/, also follow the standard-library development guidelines.

Member functions

Member functions use camelCase:

text.len();
text.at(0);
text.substr(0, 3);
text.startsWith("fl");
text.string();
text.cast<string>;
owned.cast<stringv>;

An acronym is treated as a word, such as isUtf8() rather than isUTF8(). Generic member forms such as cast<type> follow the same naming rule even when their syntax does not include parentheses. Existing language members that are already public API should be migrated to this convention before compatibility guarantees are introduced.

Free functions

Built-in and standard-library free functions use snake_case:

stdoutln("ready");
read_line();
parse_i32("42");
string_from_bytes(data);

Single-word names naturally remain lowercase, including stdout and stdoutln. Naming rules for ordinary user-defined Flecha functions are a separate language-design decision.

Compiler intrinsics and exported runtime C symbols are implementation details. Their names may follow ABI-specific conventions, such as the existing flecha_runtime_v1_ snake-case prefix, without exposing those names as the idiomatic Flecha API.