Crate iter_comprehensions
source ·Expand description
Compact iterator and vector comprehensions.
This crate implements a few macros with generating comprehension expressions.
comprehension!
for generating a sequence of index tuplesmap!
for generating a sequence of expressionsvec!
for constructing vectorssum!
for computing the sum of some valuesproduct!
for computing the product of some values
The macro comprehension!
can be used to generate a sequence of elements using
generating sequences and conditional filters.
comprehension!(i1 in RANGE1, COND1, ..., ik in RANGEk)
where RANGE* are iterators (in fact, everything implementing IntoIterator
)
and each COND* is a boolean condition. Each RANGE
and COND
term can use
the variables declared in preceding range expressions.
The macro map!
adds an additional expression that computes a value
depending on the indices:
map!(i1 in RANGE1, COND1, ..., ik in RANGEk, EXPR)
map!(EXPR; i1 in RANGE1, COND1, ..., ik in RANGEk)
Example
The expression $\{ 5i + j : i \in \{0, \ldots, 4\}, j \in \{0, \ldots, 4\}, i < j \}$ is equivalent to the following form
use iter_comprehensions::map;
assert_eq!(map!(5*i + j; i in 0..5, j in 0..5, i < j).collect::<Vec<_>>(),
vec![1, 2, 3, 4, 7, 8, 9, 13, 14, 19]);
The analogous syntax can be used to create vectors:
use iter_comprehensions::vec;
assert_eq!(vec![i; i in 0..5], vec![0,1,2,3,4]);
assert_eq!(vec![(i,j); i in 0..3, j in 0..3, i < j],
vec![(0,1), (0,2), (1,2)]);
Computing a sum of values:
use iter_comprehensions::{sum, vec};
assert_eq!(sum!(i; i in 1..10, i % 2 == 1), 25);
let S = vec![i; i in 1..10];
assert_eq!(sum!(i in S, i % 2 == 1, i), 25);
Computing a product of values:
use iter_comprehensions::product;
assert_eq!(product!(i; i in 1..=5), 120);
assert_eq!(product!(i in 1..=5, i), 120);
Macros
- A comprehension for constructing an iterator.
- A map comprehension.
- A product expression.
- A sum expression.
- Extension of
vec!
with comprehensions.