coder.nullcopy

Package: coder

Declare uninitialized variables

Syntax

X = coder.nullcopy(A)

Description

X = coder.nullcopy(A) copies type, size, and complexity of A to X, but does not copy element values. Preallocates memory for X without incurring the overhead of initializing memory.

coder.nullcopy does not support MATLAB® classes as inputs.

Use With Caution

Use this function with caution. See How to Eliminate Redundant Copies by Defining Uninitialized Variables.

Examples

The following example shows how to declare variable X as a 1-by-5 vector of real doubles without performing an unnecessary initialization:

function X = foo

N = 5;
X = coder.nullcopy(zeros(1,N));
for i = 1:N
   if mod(i,2) == 0
      X(i) = i;
   else
      X(i) = 0;
   end
end

Using coder.nullcopy with zeros lets you specify the size of vector X without initializing each element to zero.

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