Nntile Nntile Nntile

C++ coding style (Black-inspired)

Apply these rules when writing, editing, or reviewing C++ in this project. The repo root .clang-format is the canonical formatter profile; keep it aligned with this skill when either changes. For template / switch detail and edge cases, see reference.md.

Hard limits

• Line length: at most 79 characters per line (including spaces and punctuation). Prefer breaking earlier at a natural boundary when it reads better.
• Final newline: every source file must end with a newline (POSIX end-of-line), not EOF immediately after the last character.

Indentation

• 4 spaces per indent level; no tab characters for indentation.
• Wrapped expressions: indent one level past the start of the statement unless the file already uses a consistent alternative—then do not mix styles in one file.

Braces (curly brackets)

Use Allman style: { and } each on their own line for if, for, while, else, switch, try/catch, struct, class, enum class, named and anonymous namespace, and function definitions.

void foo()
{
    if (condition)
    {
        body();
    }
    else
    {
        other();
    }
}

Multi-line lambdas use Allman { / }; if the signature overflows 79 columns, break parameters like a normal function (see reference.md).

Namespaces

Opening { on its own line after the namespace header; closing } on its own line. Do not add an extra file-wide indent level for a single outer namespace unless the rest of the tree already does—match neighboring files.

Classes and structs

• class / struct: name on one line, { on the next, closing }; with } on its own line.
• Access: order sections public → protected → private; omit empty sections.
• Members (within each section): nested types / using, then static constants, then ctors / dtor / assignment, then methods (group overloads), then static methods, then data members. See reference.md for struct / = default details.

Includes

Order: associated header (in .cpp), blank line, project headers, blank line, third-party, blank line, standard library (<…>). Use #pragma once or guards as the project already does.

const, pointers, references

• Prefer east const (T const, T const&, T const*).
• Spacing: keep * and & styling consistent in the file (e.g. T *p, T const &r).

Long comments

If a comment would exceed 79 characters: split into multiple // lines (or wrapped /* */ lines), respecting word boundaries when possible.

Long function calls (Black-like)

1. ( stays on the same line as the callee (including -> / . chains).
2. First argument on the next line, indented one level.
3. If still too long: one argument per line, trailing commas between arguments, ) on its own line.

result = some_very_long_function_name(
    first_argument,
    second_argument,
    third_argument,
);

Apply the same rules recursively inside arguments. Templates (make_shared, etc.): same—( after the full callee, then break (see reference.md for multi-line template<>).

Long expressions (if, while, chains)

Break before && / || so the continuation line starts with the operator. Keep ( on the if / while line; indent continuations consistently.

Constructor initializer lists

If the list does not fit: put : after the closing ) of the ctor parameter list (or at the end of a wrapped ctor line), then one base/member init per line, comma at end of line, then Allman { on the next line after the list.

“Black spirit” (general)

• Prefer vertical layout over dense one-liners near the limit.
• One logical statement per line; spaces around binary operators and after commas in single-line lists.
• Use nullptr, not 0 / NULL, for null pointers in new code unless constrained by legacy APIs.

Checklist before finishing an edit

• No line longer than 79 characters.
• 4 spaces; no tabs for indent.
• Long comments split; long calls, conditions, ctor inits wrapped as above.
• Allman { / } for control flow, classes, namespaces, functions.
• Includes grouped and ordered; associated header first in .cpp.
• Class access / member order follows this skill.
• East const; consistent * / & spacing within the file.
• File ends with a newline.

Source: nntile/nntile — distributed by TomeVault.