rssn 0.2.9

A comprehensive scientific computing library for Rust, aiming for feature parity with NumPy and SymPy.
Documentation 
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use std::ffi::CStr;
use std::os::raw::c_char;
use std::os::raw::c_int;
use std::slice;

use crate::symbolic::core::Expr;
use crate::symbolic::number_theory::chinese_remainder;
use crate::symbolic::number_theory::extended_gcd;
use crate::symbolic::number_theory::is_prime;
use crate::symbolic::number_theory::solve_diophantine;

/// Solves a Diophantine equation.
///
/// # Safety
/// `equation` must be a valid pointer to an `Expr`.
/// `vars_ptr` must be a valid pointer to an array of C strings of length `vars_len`.
#[unsafe(no_mangle)]
pub extern "C" fn rssn_solve_diophantine_handle(
    equation: *const Expr,
    vars_ptr: *const *const c_char,
    vars_len: c_int,
) -> *mut Expr {
    let equation_ref = unsafe {
        if equation.is_null() {
            return std::ptr::null_mut();
        }

        &*equation
    };

    let vars: Vec<String> = unsafe {
        slice::from_raw_parts(vars_ptr, vars_len.try_into().unwrap_or(0))
            .iter()
            .map(|&p| CStr::from_ptr(p).to_string_lossy().into_owned())
            .collect()
    };

    let vars_str: Vec<&str> = vars.iter().map(std::string::String::as_str).collect();

    match solve_diophantine(equation_ref, &vars_str) {
        | Ok(solutions) => {
            let result = Expr::new_vector(solutions);

            Box::into_raw(Box::new(result))
        },
        | Err(_) => std::ptr::null_mut(),
    }
}

/// Computes the Extended GCD of two expressions.
///
/// # Safety
/// `a` and `b` must be valid pointers to `Expr`.
#[unsafe(no_mangle)]
pub extern "C" fn rssn_extended_gcd_handle(
    a: *const Expr,
    b: *const Expr,
) -> *mut Expr {
    let a_ref = unsafe {
        if a.is_null() {
            return std::ptr::null_mut();
        }

        &*a
    };

    let b_ref = unsafe {
        if b.is_null() {
            return std::ptr::null_mut();
        }

        &*b
    };

    let (g, x, y) = extended_gcd(a_ref, b_ref);

    let result = Expr::new_tuple(vec![g, x, y]);

    Box::into_raw(Box::new(result))
}

/// Checks if an expression is prime.
///
/// # Safety
/// `n` must be a valid pointer to an `Expr`.
#[unsafe(no_mangle)]
pub extern "C" fn rssn_is_prime_handle(n: *const Expr) -> *mut Expr {
    let n_ref = unsafe {
        if n.is_null() {
            return std::ptr::null_mut();
        }

        &*n
    };

    let result = is_prime(n_ref);

    Box::into_raw(Box::new(result))
}

/// Solves a system of congruences using the Chinese Remainder Theorem.
///
/// # Safety
/// `remainders` and `moduli` must be valid pointers to arrays of `Expr` pointers of length `len`.
#[unsafe(no_mangle)]
pub extern "C" fn rssn_chinese_remainder_handle(
    remainders: *const *const Expr,
    moduli: *const *const Expr,
    len: c_int,
) -> *mut Expr {
    let remainders_slice =
        unsafe { slice::from_raw_parts(remainders, len.try_into().unwrap_or(0)) };

    let moduli_slice = unsafe { slice::from_raw_parts(moduli, len.try_into().unwrap_or(0)) };

    let mut congruences = Vec::new();

    for i in 0..len.try_into().unwrap_or(0) {
        let r_ptr = remainders_slice[i];

        let m_ptr = moduli_slice[i];

        if r_ptr.is_null() || m_ptr.is_null() {
            return std::ptr::null_mut();
        }

        let r = unsafe { &*r_ptr };

        let m = unsafe { &*m_ptr };

        congruences.push((r.clone(), m.clone()));
    }

    match chinese_remainder(&congruences) {
        | Some(result) => Box::into_raw(Box::new(result)),
        | None => std::ptr::null_mut(),
    }
}