true — Create logical arrays filled with true values.

true creates logical arrays filled with true values. RunMat mirrors MATLAB sizing semantics across scalar, vector, matrix, and N-D forms.

How true works in RunMat

• true() returns the scalar logical true.
• true(n) returns an n x n logical array of true values.
• true(m, n, ...) returns a logical array with the requested dimensions.
• true(sz) accepts a size vector (row or column) and returns an array with prod(sz) elements arranged using MATLAB column-major ordering.
• true(A) returns a logical array of true with the same size as A.
• true(___, 'like', prototype) uses the prototype only for sizing; the result is still a host logical array.
• true(___, 'logical') is accepted for MATLAB compatibility and has no effect.

Examples

Creating a 2x3 logical array of true values

mask = true(2, 3)

Expected output:

mask = [1 1 1; 1 1 1]

Creating a logical array from a size vector

dims = [2 1 3];
mask = true(dims)

Expected output:

mask =
  2x1x3 logical array
     1
     1
     1
     1
     1
     1

Creating a true mask with the same size as an existing array

A = rand(3, 2);
mask = true(A)

Expected output:

mask =
  3x2 logical array
     1     1
     1     1
     1     1

FAQ

What does true() return?

It returns the logical scalar true.

Does true(n) create a square array?

Yes. true(n) returns an n x n logical array of true values, matching MATLAB behavior.

How does true(sz) interpret a size vector?

A row or column vector is treated as the full set of dimensions, so true([2 3 4]) yields a 2x3x4 logical array.

Does true keep results on the GPU?

No. The builtin always returns a host logical array. gpuArray inputs are only used to infer the output size.

Is the 'logical' option required?

No. true always returns logical values; the 'logical' option is accepted only for MATLAB compatibility.

Related functions to explore

These functions work well alongside true. Each page has runnable examples you can try in the browser.

false, logical, islogical, zeros, colon, eye, fill, linspace, logspace, magic, meshgrid, ones, rand, randi, randn, randperm, range

Open-source implementation

Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how true works, line by line, in Rust.

• View true.rs on GitHub
• Learn how the runtime works
• Found a bug? Open an issue with a minimal reproduction.

About RunMat

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• Simulations that took hours now take minutes. RunMat automatically optimizes your math for GPU execution on Apple, Nvidia, and AMD hardware. No code changes needed.
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