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use crate::{
    matrix::{operations::identity::identity, Matrix},
    types::PositiveDefinite,
};
use lapack::dposv;

impl Matrix<PositiveDefinite> {
    /// # Inverse
    /// for PositiveDefinite Matrix
    pub fn inv(mut self) -> Result<Matrix<PositiveDefinite>, String> {
        if self.rows != self.columns {
            return Err("dimension mismatch".to_owned());
        }

        let mut solution_matrix = identity(self.rows).transmute();

        let mut info = 0;

        unsafe {
            dposv(
                'U' as u8,
                self.rows as i32,
                self.rows as i32,
                &mut self.elements,
                self.rows as i32,
                &mut solution_matrix.elements,
                self.rows as i32,
                &mut info,
            );
        }

        match info {
            0 => Ok(solution_matrix),
            i => Err(i.to_string()),
        }
    }
}