coder.mustBeConst
Syntax
Description
coder.mustBeConst(
validates that the
function input value
)value
is a constant during code generation, also
referred to as a compile-time constant in this context. During code
generation, this function throws an error if value
is not a
compile-time constant. During MATLAB® execution, this function has no
effect.
Examples
Validate That Input is a Compile-Time Constant
This example shows how to validate that an input to a function that is called from the entry-point function is a constant during code generation, also referred to as a compile-time constant.
Define an entry-point function testConstant
that calls a local
function local
. The first input to the local function is validated to
be a compile-time constant using the coder.mustBeConst
validator.
function out = testConst(in1,in2) if in1 > 0 out = local(in1,in2); else out = local(-in1,in2); end end function u = local(x,y) arguments x {coder.mustBeConst} y end u = sqrt(x) + y; end
Generate code for the testConst
function using the
codegen
command. Specify the entry-point inputs
in1
and in2
to be scalar doubles using the
-args
option.
codegen testConst -args {0,0}
Value must be constant. Error in ==> testConst Line: 11 Column: 8 Code generation failed: View Error Report
Code generation fails because the absolute value of the run-time input
in1
is directly passed as the first argument when calling the
function local
. Because this value is not known at compile time, the
coder.mustBeConst
validator throws an error during code
generation.
Modify the codegen
command by specifying the first entry-point
input to be of a constant type using the coder.Constant
(MATLAB Coder) function.
codegen testConst -args {coder.Constant(0),0}
Code generation successful.
Because the first input passed to local
is of a constant type,
the coder.mustBeConst
validator does not throw an error and code
generation succeeds.
Input Arguments
value
— Value to validate
scalar | array
Value to validate as a compile-time constant, specified as a scalar or array of one
of the data types listed below. This argument can also be an instance of a value class
that you authored. Passing handle objects to coder.mustBeConst
is not
supported.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
| logical
| char
| string
| struct
| cell
| function_handle
| categorical
| datetime
| duration
| fi
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.
Version History
Introduced in R2023b
See Also
codegen
(MATLAB Coder)
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