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//
// A rust binding for the GSL library by Guillaume Gomez (guillaume1.gomez@gmail.com)
//
/*!
# Combinations
This chapter describes functions for creating and manipulating combinations. A combination c is
represented by an array of k integers in the range 0 to n-1, where each value c_i occurs at most
once. The combination c corresponds to indices of k elements chosen from an n element vector.
Combinations are useful for iterating over all k-element subsets of a set.
## References and Further Reading
Further information on combinations can be found in,
Donald L. Kreher, Douglas R. Stinson, Combinatorial Algorithms: Generation, Enumeration and Search,
1998, CRC Press LLC, ISBN 084933988X
!*/
use crate::Value;
use ffi::FFI;
use std::fmt::{self, Debug, Formatter};
ffi_wrapper!(Combination, *mut sys::gsl_combination, gsl_combination_free);
impl Combination {
/// This function allocates memory for a new combination with parameters n, k. The combination
/// is not initialized and its elements are undefined. Use the function
/// `Combination::new_init_first` if you want to create a combination which is initialized to
/// the lexicographically first combination. A null pointer is returned if insufficient memory
/// is available to create the combination.
#[doc(alias = "gsl_combination_alloc")]
pub fn new(n: usize, k: usize) -> Option<Self> {
let tmp = unsafe { sys::gsl_combination_alloc(n, k) };
if tmp.is_null() {
None
} else {
Some(Self::wrap(tmp))
}
}
/// This function allocates memory for a new combination with parameters n, k and initializes it
/// to the lexicographically first combination. A null pointer is returned if insufficient
/// memory is available to create the combination.
#[doc(alias = "gsl_combination_calloc")]
pub fn new_with_init(n: usize, k: usize) -> Option<Self> {
let tmp = unsafe { sys::gsl_combination_calloc(n, k) };
if tmp.is_null() {
None
} else {
Some(Self::wrap(tmp))
}
}
/// This function initializes the combination c to the lexicographically first combination, i.e.
/// (0,1,2,...,k-1).
#[doc(alias = "gsl_combination_init_first")]
pub fn init_first(&mut self) {
unsafe { sys::gsl_combination_init_first(self.unwrap_unique()) }
}
/// This function initializes the combination c to the lexicographically last combination, i.e.
/// (n-k,n-k+1,…,n-1).
#[doc(alias = "gsl_combination_init_last")]
pub fn init_last(&mut self) {
unsafe { sys::gsl_combination_init_last(self.unwrap_unique()) }
}
/// This function copies the elements of the combination self into the combination dest. The two
/// combinations must have the same size.
#[doc(alias = "gsl_combination_memcpy")]
pub fn copy(&self, dest: &mut Combination) -> Value {
Value::from(unsafe {
sys::gsl_combination_memcpy(dest.unwrap_unique(), self.unwrap_shared())
})
}
/// This function returns the value of the i-th element of the combination self. If i lies
/// outside the allowed range of 0 to k-1 then the error handler is invoked and 0 is returned.
#[doc(alias = "gsl_combination_get")]
pub fn get(&self, i: usize) -> usize {
unsafe { sys::gsl_combination_get(self.unwrap_shared(), i) }
}
/// This function returns the range (n) of the combination self.
#[doc(alias = "gsl_combination_n")]
pub fn n(&self) -> usize {
unsafe { sys::gsl_combination_n(self.unwrap_shared()) }
}
/// This function returns the number of elements (k) in the combination self.
#[doc(alias = "gsl_combination_k")]
pub fn k(&self) -> usize {
unsafe { sys::gsl_combination_k(self.unwrap_shared()) }
}
// checker:ignore
#[doc(alias = "gsl_combination_data")]
pub fn as_slice(&self) -> &[usize] {
unsafe {
let data = sys::gsl_combination_data(self.unwrap_shared());
::std::slice::from_raw_parts(data, self.k())
}
}
// checker:ignore
#[doc(alias = "gsl_combination_data")]
pub fn as_mut_slice(&mut self) -> &mut [usize] {
unsafe {
let data = sys::gsl_combination_data(self.unwrap_shared());
::std::slice::from_raw_parts_mut(data, self.k())
}
}
/// This function checks that the combination self is valid. The k elements should lie in the
/// range 0 to n-1, with each value occurring once at most and in increasing order.
// checker:ignore
#[doc(alias = "gsl_combination_valid")]
pub fn is_valid(&self) -> Value {
// Little hack because `gsl_combination_valid` doesn't in fact need a mutable object...
Value::from(unsafe { sys::gsl_combination_valid(self.inner) })
}
/// This function advances the combination self to the next combination in lexicographic order
/// and returns `Success`. If no further combinations are available it returns Failure and
/// leaves self unmodified. Starting with the first combination and repeatedly applying this
/// function will iterate through all possible combinations of a given order.
#[doc(alias = "gsl_combination_next")]
pub fn next(&mut self) -> Value {
Value::from(unsafe { sys::gsl_combination_next(self.unwrap_unique()) })
}
/// This function steps backwards from the combination self to the previous combination in
/// lexicographic order, returning `Success`. If no previous combination is available it returns
/// `Failure` and leaves self unmodified.
#[doc(alias = "gsl_combination_prev")]
pub fn prev(&mut self) -> Value {
Value::from(unsafe { sys::gsl_combination_prev(self.unwrap_unique()) })
}
}
impl Debug for Combination {
#[allow(unused_must_use)]
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
write!(f, "[");
let s = self.as_slice();
for (pos, v) in s.iter().enumerate() {
if pos == 0 {
write!(f, "{}", v).unwrap();
} else {
write!(f, " {}", v).unwrap();
}
}
write!(f, "]")
}
}