rssn 0.2.9

A comprehensive scientific computing library for Rust, aiming for feature parity with NumPy and SymPy.
Documentation 
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//! JSON-based FFI for polynomial operations

use std::os::raw::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::polynomial::contains_var;
use crate::symbolic::polynomial::is_polynomial;
use crate::symbolic::polynomial::leading_coefficient;
use crate::symbolic::polynomial::polynomial_degree;
use crate::symbolic::polynomial::polynomial_long_division;
use crate::symbolic::polynomial::to_polynomial_coeffs_vec;

/// Checks if an expression is a polynomial in the given variable (JSON)
#[unsafe(no_mangle)]
pub extern "C" fn rssn_json_polynomial_is_polynomial(
    expr_json: *const c_char,
    var: *const c_char,
) -> bool {
    let expr: Option<Expr> = from_json_string(expr_json);

    let var_str = unsafe {
        if var.is_null() {
            None
        } else {
            std::ffi::CStr::from_ptr(var).to_str().ok()
        }
    };

    match (expr, var_str) {
        | (Some(e), Some(v)) => is_polynomial(&e, v),
        | _ => false,
    }
}

/// Computes the degree of a polynomial (JSON)
#[unsafe(no_mangle)]
pub extern "C" fn rssn_json_polynomial_degree(
    expr_json: *const c_char,
    var: *const c_char,
) -> i64 {
    let expr: Option<Expr> = from_json_string(expr_json);

    let var_str = unsafe {
        if var.is_null() {
            None
        } else {
            std::ffi::CStr::from_ptr(var).to_str().ok()
        }
    };

    match (expr, var_str) {
        | (Some(e), Some(v)) => polynomial_degree(&e, v),
        | _ => -1,
    }
}

/// Performs polynomial long division (JSON)
#[unsafe(no_mangle)]
pub extern "C" fn rssn_json_polynomial_long_division(
    dividend_json: *const c_char,
    divisor_json: *const c_char,
    var: *const c_char,
) -> *mut c_char {
    let dividend: Option<Expr> = from_json_string(dividend_json);

    let divisor: Option<Expr> = from_json_string(divisor_json);

    let var_str = unsafe {
        if var.is_null() {
            None
        } else {
            std::ffi::CStr::from_ptr(var).to_str().ok()
        }
    };

    match (dividend, divisor, var_str) {
        | (Some(d), Some(div), Some(v)) => {
            let (quotient, remainder) = polynomial_long_division(&d, &div, v);

            let result = serde_json::json!({
                "quotient": quotient,
                "remainder": remainder
            });

            to_json_string(&result)
        },
        | _ => std::ptr::null_mut(),
    }
}

/// Finds the leading coefficient of a polynomial (JSON)
#[unsafe(no_mangle)]
pub extern "C" fn rssn_json_polynomial_leading_coefficient(
    expr_json: *const c_char,
    var: *const c_char,
) -> *mut c_char {
    let expr: Option<Expr> = from_json_string(expr_json);

    let var_str = unsafe {
        if var.is_null() {
            None
        } else {
            std::ffi::CStr::from_ptr(var).to_str().ok()
        }
    };

    match (expr, var_str) {
        | (Some(e), Some(v)) => {
            let result = leading_coefficient(&e, v);

            to_json_string(&result)
        },
        | _ => std::ptr::null_mut(),
    }
}

/// Converts polynomial to coefficient vector (JSON)
#[unsafe(no_mangle)]
pub extern "C" fn rssn_json_polynomial_to_coeffs_vec(
    expr_json: *const c_char,
    var: *const c_char,
) -> *mut c_char {
    let expr: Option<Expr> = from_json_string(expr_json);

    let var_str = unsafe {
        if var.is_null() {
            None
        } else {
            std::ffi::CStr::from_ptr(var).to_str().ok()
        }
    };

    match (expr, var_str) {
        | (Some(e), Some(v)) => {
            let coeffs = to_polynomial_coeffs_vec(&e, v);

            to_json_string(&coeffs)
        },
        | _ => std::ptr::null_mut(),
    }
}

/// Checks if an expression contains a variable (JSON)
#[unsafe(no_mangle)]
pub extern "C" fn rssn_json_polynomial_contains_var(
    expr_json: *const c_char,
    var: *const c_char,
) -> bool {
    let expr: Option<Expr> = from_json_string(expr_json);

    let var_str = unsafe {
        if var.is_null() {
            None
        } else {
            std::ffi::CStr::from_ptr(var).to_str().ok()
        }
    };

    match (expr, var_str) {
        | (Some(e), Some(v)) => contains_var(&e, v),
        | _ => false,
    }
}