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_double;

use crate::symbolic::core::Expr;
use crate::symbolic::polynomial::expr_to_sparse_poly;
use crate::symbolic::polynomial::sparse_poly_to_expr;
use crate::symbolic::real_roots::count_real_roots_in_interval;
use crate::symbolic::real_roots::isolate_real_roots;
use crate::symbolic::real_roots::sturm_sequence;

/// Generates the Sturm sequence for a given polynomial (Handle)
#[unsafe(no_mangle)]
pub extern "C" fn rssn_sturm_sequence_handle(
    expr_ptr: *const Expr,
    var_ptr: *const c_char,
) -> *mut Vec<Expr> {
    if expr_ptr.is_null() || var_ptr.is_null() {
        return std::ptr::null_mut();
    }

    unsafe {
        let expr = &*expr_ptr;

        let var_cstr = CStr::from_ptr(var_ptr);

        let var_str = match var_cstr.to_str() {
            | Ok(s) => s,
            | Err(_) => return std::ptr::null_mut(),
        };

        // Convert Expr to SparsePolynomial
        // Note: expr_to_sparse_poly requires a list of variables if we want to be precise,
        // but here we are treating it as a univariate polynomial in `var`.
        // The implementation in integration.rs used `expr_to_sparse_poly(expr, &[var])`.
        let poly = expr_to_sparse_poly(expr, &[var_str]);

        let seq = sturm_sequence(&poly, var_str);

        // Convert back to Exprs
        let expr_seq: Vec<Expr> = seq.into_iter().map(|p| sparse_poly_to_expr(&p)).collect();

        Box::into_raw(Box::new(expr_seq))
    }
}

/// Counts the number of distinct real roots in an interval (Handle)
#[unsafe(no_mangle)]
pub extern "C" fn rssn_count_real_roots_in_interval_handle(
    expr_ptr: *const Expr,
    var_ptr: *const c_char,
    a: c_double,
    b: c_double,
) -> i64 {
    if expr_ptr.is_null() || var_ptr.is_null() {
        return -1;
    }

    unsafe {
        let expr = &*expr_ptr;

        let var_cstr = CStr::from_ptr(var_ptr);

        let var_str = match var_cstr.to_str() {
            | Ok(s) => s,
            | Err(_) => return -1,
        };

        let poly = expr_to_sparse_poly(expr, &[var_str]);

        match count_real_roots_in_interval(&poly, var_str, a, b) {
            | Ok(count) => count as i64,
            | Err(_) => -1,
        }
    }
}

/// Isolates real roots in an interval (Handle)
/// Returns a pointer to a Vec<(f64, f64)>
#[unsafe(no_mangle)]
pub extern "C" fn rssn_isolate_real_roots_handle(
    expr_ptr: *const Expr,
    var_ptr: *const c_char,
    precision: c_double,
) -> *mut Vec<(f64, f64)> {
    if expr_ptr.is_null() || var_ptr.is_null() {
        return std::ptr::null_mut();
    }

    unsafe {
        let expr = &*expr_ptr;

        let var_cstr = CStr::from_ptr(var_ptr);

        let var_str = match var_cstr.to_str() {
            | Ok(s) => s,
            | Err(_) => return std::ptr::null_mut(),
        };

        let poly = expr_to_sparse_poly(expr, &[var_str]);

        match isolate_real_roots(&poly, var_str, precision) {
            | Ok(roots) => Box::into_raw(Box::new(roots)),
            | Err(_) => std::ptr::null_mut(),
        }
    }
}

/// Frees a `Vec<Expr>` handle
#[unsafe(no_mangle)]
pub extern "C" fn rssn_free_expr_vec_handle(ptr: *mut Vec<Expr>) {
    if !ptr.is_null() {
        unsafe {
            let _ = Box::from_raw(ptr);
        }
    }
}

/// Frees a Vec<(f64, f64)> handle
#[unsafe(no_mangle)]
pub extern "C" fn rssn_free_interval_vec_handle(ptr: *mut Vec<(f64, f64)>) {
    if !ptr.is_null() {
        unsafe {
            let _ = Box::from_raw(ptr);
        }
    }
}