rssn 0.2.9

A comprehensive scientific computing library for Rust, aiming for feature parity with NumPy and SymPy.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68

//! JSON-based FFI API for classical mechanics functions.

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::classical_mechanics;
use crate::symbolic::core::Expr;

/// Calculates kinetic energy using JSON.
#[unsafe(no_mangle)]
pub extern "C" fn rssn_json_kinetic_energy(
    mass_json: *const c_char,
    velocity_json: *const c_char,
) -> *mut c_char {
    let mass: Option<Expr> = from_json_string(mass_json);

    let velocity: Option<Expr> = from_json_string(velocity_json);

    match (mass, velocity) {
        | (Some(m), Some(v)) => to_json_string(&classical_mechanics::kinetic_energy(&m, &v)),
        | _ => std::ptr::null_mut(),
    }
}

/// Computes Euler-Lagrange equation using JSON.
#[unsafe(no_mangle)]
pub extern "C" fn rssn_json_euler_lagrange_equation(
    lagrangian_json: *const c_char,
    q: *const c_char,
    q_dot: *const c_char,
    t_var: *const c_char,
) -> *mut c_char {
    let lagrangian: Option<Expr> = from_json_string(lagrangian_json);

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

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

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

    match (lagrangian, q_str, q_dot_str, t_str) {
        | (Some(l), Some(qs), Some(qds), Some(ts)) => {
            to_json_string(&classical_mechanics::euler_lagrange_equation(
                &l, qs, qds, ts,
            ))
        },
        | _ => std::ptr::null_mut(),
    }
}