rssn 0.2.9

A comprehensive scientific computing library for Rust, aiming for feature parity with NumPy and SymPy.
Documentation 
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//! Handle-based FFI API for numerical combinatorics.

use std::slice;

use crate::ffi_apis::ffi_api::update_last_error;
use crate::numerical::combinatorics;

/// Computes the factorial of n.
///
/// # Safety
///
/// This function is unsafe because it dereferences raw pointers as part of the FFI boundary.
/// The caller must ensure:
/// 1. All pointer arguments are valid and point to initialized memory.
/// 2. The memory layout of passed structures matches the expected C-ABI layout.
/// 3. Any pointers returned by this function are managed according to the API's ownership rules.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_comb_factorial(
    n: u64,
    result: *mut f64,
) -> i32 {
    unsafe {
        if result.is_null() {
            update_last_error(
                "Null pointer passed to \
             rssn_num_comb_factorial"
                    .to_string(),
            );

            return -1;
        }

        *result = combinatorics::factorial(n);

        0
    }
}

/// Computes the number of permutations P(n, k).
///
/// # Safety
///
/// This function is unsafe because it dereferences raw pointers as part of the FFI boundary.
/// The caller must ensure:
/// 1. All pointer arguments are valid and point to initialized memory.
/// 2. The memory layout of passed structures matches the expected C-ABI layout.
/// 3. Any pointers returned by this function are managed according to the API's ownership rules.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_comb_permutations(
    n: u64,
    k: u64,
    result: *mut f64,
) -> i32 {
    unsafe {
        if result.is_null() {
            update_last_error("Null pointer passed to rssn_num_comb_permutations".to_string());

            return -1;
        }

        *result = combinatorics::permutations(n, k);

        0
    }
}

/// Computes the number of combinations C(n, k).
///
/// # Safety
///
/// This function is unsafe because it dereferences raw pointers as part of the FFI boundary.
/// The caller must ensure:
/// 1. All pointer arguments are valid and point to initialized memory.
/// 2. The memory layout of passed structures matches the expected C-ABI layout.
/// 3. Any pointers returned by this function are managed according to the API's ownership rules.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_comb_combinations(
    n: u64,
    k: u64,
    result: *mut f64,
) -> i32 {
    unsafe {
        if result.is_null() {
            update_last_error("Null pointer passed to rssn_num_comb_combinations".to_string());

            return -1;
        }

        *result = combinatorics::combinations(n, k);

        0
    }
}

/// Solves a linear recurrence relation numerically.
///
/// # Safety
///
/// This function is unsafe because it dereferences raw pointers as part of the FFI boundary.
/// The caller must ensure:
/// 1. All pointer arguments are valid and point to initialized memory.
/// 2. The memory layout of passed structures matches the expected C-ABI layout.
/// 3. Any pointers returned by this function are managed according to the API's ownership rules.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_comb_solve_recurrence(
    coeffs: *const f64,
    coeffs_len: usize,
    initial_conditions: *const f64,
    initial_len: usize,
    target_n: usize,
    result: *mut f64,
) -> i32 {
    unsafe {
        if coeffs.is_null() || initial_conditions.is_null() || result.is_null() {
            update_last_error("Null pointer passed to rssn_num_comb_solve_recurrence".to_string());

            return -1;
        }

        let coeffs_slice = slice::from_raw_parts(coeffs, coeffs_len);

        let initial_slice = slice::from_raw_parts(initial_conditions, initial_len);

        match combinatorics::solve_recurrence_numerical(coeffs_slice, initial_slice, target_n) {
            | Ok(val) => {
                *result = val;

                0
            },
            | Err(e) => {
                update_last_error(e);

                -1
            },
        }
    }
}

/// Computes the Stirling numbers of the second kind S(n, k).
///
/// # Safety
///
/// This function is unsafe because it dereferences raw pointers as part of the FFI boundary.
/// The caller must ensure:
/// 1. All pointer arguments are valid and point to initialized memory.
/// 2. The memory layout of passed structures matches the expected C-ABI layout.
/// 3. Any pointers returned by this function are managed according to the API's ownership rules.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_comb_stirling_second(
    n: u64,
    k: u64,
    result: *mut f64,
) -> i32 {
    unsafe {
        if result.is_null() {
            update_last_error("Null pointer passed to rssn_num_comb_stirling_second".to_string());

            return -1;
        }

        *result = combinatorics::stirling_second(n, k);

        0
    }
}

/// Computes the Bell number B(n).
///
/// # Safety
///
/// This function is unsafe because it dereferences raw pointers as part of the FFI boundary.
/// The caller must ensure:
/// 1. All pointer arguments are valid and point to initialized memory.
/// 2. The memory layout of passed structures matches the expected C-ABI layout.
/// 3. Any pointers returned by this function are managed according to the API's ownership rules.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_comb_bell(
    n: u64,
    result: *mut f64,
) -> i32 {
    unsafe {
        if result.is_null() {
            update_last_error(
                "Null pointer passed \
                 to rssn_num_comb_bell"
                    .to_string(),
            );

            return -1;
        }

        *result = combinatorics::bell(n);

        0
    }
}

/// Computes the Catalan number `C_n`.
///
/// # Safety
///
/// This function is unsafe because it dereferences raw pointers as part of the FFI boundary.
/// The caller must ensure:
/// 1. All pointer arguments are valid and point to initialized memory.
/// 2. The memory layout of passed structures matches the expected C-ABI layout.
/// 3. Any pointers returned by this function are managed according to the API's ownership rules.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_comb_catalan(
    n: u64,
    result: *mut f64,
) -> i32 {
    unsafe {
        if result.is_null() {
            update_last_error(
                "Null pointer passed to \
             rssn_num_comb_catalan"
                    .to_string(),
            );

            return -1;
        }

        *result = combinatorics::catalan(n);

        0
    }
}

/// Computes the rising factorial.
///
/// # Safety
///
/// This function is unsafe because it dereferences raw pointers as part of the FFI boundary.
/// The caller must ensure:
/// 1. All pointer arguments are valid and point to initialized memory.
/// 2. The memory layout of passed structures matches the expected C-ABI layout.
/// 3. Any pointers returned by this function are managed according to the API's ownership rules.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_comb_rising_factorial(
    x: f64,
    n: u64,
    result: *mut f64,
) -> i32 {
    unsafe {
        if result.is_null() {
            update_last_error("Null pointer passed to rssn_num_comb_rising_factorial".to_string());

            return -1;
        }

        *result = combinatorics::rising_factorial(x, n);

        0
    }
}

/// Computes the falling factorial.
///
/// # Safety
///
/// This function is unsafe because it dereferences raw pointers as part of the FFI boundary.
/// The caller must ensure:
/// 1. All pointer arguments are valid and point to initialized memory.
/// 2. The memory layout of passed structures matches the expected C-ABI layout.
/// 3. Any pointers returned by this function are managed according to the API's ownership rules.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_comb_falling_factorial(
    x: f64,
    n: u64,
    result: *mut f64,
) -> i32 {
    unsafe {
        if result.is_null() {
            update_last_error("Null pointer passed to rssn_num_comb_falling_factorial".to_string());

            return -1;
        }

        *result = combinatorics::falling_factorial(x, n);

        0
    }
}