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docs: demonstrate matrix! and vector! macros in construction example #1604

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47 changes: 33 additions & 14 deletions examples/matrix_construction.rs
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Original file line number Diff line number Diff line change
@@ -1,50 +1,68 @@
extern crate nalgebra as na;

use na::{DMatrix, Matrix2x3, RowVector3, Vector2};
use na::{DMatrix, DVector, Matrix2x3, RowVector3, Vector2};

fn main() {
// All the following matrices are equal but constructed in different ways.
let m = Matrix2x3::new(1.1, 1.2, 1.3, 2.1, 2.2, 2.3);
// For small matrices known directly from their entries, the matrix! macro
// is the preferred construction method. Entries are written row-by-row,
// with commas separating columns and semicolons separating rows.
let m = na::matrix![1.1, 1.2, 1.3;
2.1, 2.2, 2.3];

let m1 = Matrix2x3::from_rows(&[
let m1 = Matrix2x3::new(1.1, 1.2, 1.3, 2.1, 2.2, 2.3);

let m2 = Matrix2x3::from_rows(&[
RowVector3::new(1.1, 1.2, 1.3),
RowVector3::new(2.1, 2.2, 2.3),
]);

let m2 = Matrix2x3::from_columns(&[
let m3 = Matrix2x3::from_columns(&[
Vector2::new(1.1, 2.1),
Vector2::new(1.2, 2.2),
Vector2::new(1.3, 2.3),
]);

let m3 = Matrix2x3::from_row_slice(&[1.1, 1.2, 1.3, 2.1, 2.2, 2.3]);
let m4 = Matrix2x3::from_row_slice(&[1.1, 1.2, 1.3, 2.1, 2.2, 2.3]);

let m4 = Matrix2x3::from_column_slice(&[1.1, 2.1, 1.2, 2.2, 1.3, 2.3]);
let m5 = Matrix2x3::from_column_slice(&[1.1, 2.1, 1.2, 2.2, 1.3, 2.3]);

let m5 = Matrix2x3::from_fn(|r, c| (r + 1) as f32 + (c + 1) as f32 / 10.0);
let m6 = Matrix2x3::from_fn(|r, c| (r + 1) as f32 + (c + 1) as f32 / 10.0);

let m6 = Matrix2x3::from_iterator([1.1f32, 2.1, 1.2, 2.2, 1.3, 2.3].iter().cloned());
let m7 = Matrix2x3::from_iterator([1.1f32, 2.1, 1.2, 2.2, 1.3, 2.3].iter().cloned());

assert_eq!(m, m1);
assert_eq!(m, m2);
assert_eq!(m, m3);
assert_eq!(m, m4);
assert_eq!(m, m5);
assert_eq!(m, m6);
assert_eq!(m, m7);

// For fixed-size vectors, use vector!. Dynamic vectors use dvector!.
let v = na::vector![1.0, 2.0];
let dv = na::dvector![1.0, 2.0, 3.0];

assert_eq!(v, Vector2::new(1.0, 2.0));
assert_eq!(dv, DVector::from_column_slice(&[1.0, 2.0, 3.0]));

// All the following matrices are equal but constructed in different ways.
// This time, we used a dynamically-sized matrix to show the extra arguments
// for the matrix shape.
let dm = DMatrix::from_row_slice(
let dm = na::dmatrix![1.0, 0.0, 0.0;
0.0, 1.0, 0.0;
0.0, 0.0, 1.0;
0.0, 0.0, 0.0];

let dm1 = DMatrix::from_row_slice(
4,
3,
&[1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0],
);

let dm1 = DMatrix::from_diagonal_element(4, 3, 1.0);
let dm2 = DMatrix::identity(4, 3);
let dm3 = DMatrix::from_fn(4, 3, |r, c| if r == c { 1.0 } else { 0.0 });
let dm4 = DMatrix::from_iterator(
let dm2 = DMatrix::from_diagonal_element(4, 3, 1.0);
let dm3 = DMatrix::identity(4, 3);
let dm4 = DMatrix::from_fn(4, 3, |r, c| if r == c { 1.0 } else { 0.0 });
let dm5 = DMatrix::from_iterator(
4,
3,
[
Expand All @@ -59,4 +77,5 @@ fn main() {
assert_eq!(dm, dm2);
assert_eq!(dm, dm3);
assert_eq!(dm, dm4);
assert_eq!(dm, dm5);
}