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::c_char;

use crate::ffi_apis::common::from_json_string;
use crate::ffi_apis::common::to_json_string;
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;

#[derive(serde::Deserialize)]
struct Congruence {
    remainder: Expr,
    modulus: Expr,
}

/// Solves a Diophantine equation.
/// Takes JSON strings representing the equation (`Expr`) and variables (`Vec<String>`),
/// and returns a JSON string representing the `Vec<Expr>` of solutions.
#[unsafe(no_mangle)]
pub extern "C" fn rssn_json_solve_diophantine(
    equation_json: *const c_char,
    vars_json: *const c_char,
) -> *mut c_char {
    let equation: Option<Expr> = from_json_string(equation_json);

    let vars: Option<Vec<String>> = from_json_string(vars_json);

    match (equation, vars) {
        | (Some(eq), Some(v)) => {
            let v_str: Vec<&str> = v.iter().map(std::string::String::as_str).collect();

            match solve_diophantine(&eq, &v_str) {
                | Ok(solutions) => to_json_string(&solutions),
                | Err(_) => std::ptr::null_mut(),
            }
        },
        | _ => std::ptr::null_mut(),
    }
}

/// Computes the extended greatest common divisor (GCD).
///
/// Takes JSON strings representing two numbers (`a` and `b`),
/// and returns a JSON string representing a tuple `(g, x, y)` where `g` is the GCD
/// and `x`, `y` are coefficients such that `ax + by = g`.
#[unsafe(no_mangle)]
pub extern "C" fn rssn_json_extended_gcd(
    a_json: *const c_char,
    b_json: *const c_char,
) -> *mut c_char {
    let a: Option<Expr> = from_json_string(a_json);

    let b: Option<Expr> = from_json_string(b_json);

    match (a, b) {
        | (Some(a_expr), Some(b_expr)) => {
            let (g, x, y) = extended_gcd(&a_expr, &b_expr);

            to_json_string(&(g, x, y))
        },
        | _ => std::ptr::null_mut(),
    }
}

/// Checks if a number is prime.
/// Takes a JSON string representing an `Expr` (number),
/// and returns a JSON string representing a boolean indicating whether the number is prime.
#[unsafe(no_mangle)]
pub extern "C" fn rssn_json_is_prime(n_json: *const c_char) -> *mut c_char {
    let n: Option<Expr> = from_json_string(n_json);

    if let Some(n_expr) = n {
        let result = is_prime(&n_expr);

        to_json_string(&result)
    } else {
        std::ptr::null_mut()
    }
}

/// Solves the Chinese Remainder Theorem.
/// Takes a JSON string representing a vector of congruences (`(remainder, modulus)`),
/// and returns a JSON string representing the `Expr` solution.
#[unsafe(no_mangle)]
pub extern "C" fn rssn_json_chinese_remainder(congruences_json: *const c_char) -> *mut c_char {
    let congruences_input: Option<Vec<Congruence>> = from_json_string(congruences_json);

    if let Some(input) = congruences_input {
        let congruences: Vec<(Expr, Expr)> = input
            .into_iter()
            .map(|c| (c.remainder, c.modulus))
            .collect();

        match chinese_remainder(&congruences) {
            | Some(result) => to_json_string(&result),
            | None => std::ptr::null_mut(),
        }
    } else {
        std::ptr::null_mut()
    }
}