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Function Definition

Defining and calling functions for code generation

There are special considerations when you create MATLAB® functions that are intended for code generation. These include certain restrictions when you use varargin and varargout, recursive functions, anonymous functions, and nested functions. To generate code for MATLAB recursive functions, the code generator uses either compile-time recursion or run-time recursion. To produce efficient C/C++ code, the code generator sometimes creates multiple versions of a function, referred to as function specializations. In certain cases, you can prevent the code generator from creating function specializations by using coder.ignoreConst and coder.ignoreSize. While generating a MEX function, you can bypass code generation for a specific function in your MATLAB code and instead use the MATLAB engine to execute the call. To do this, use the coder.extrinsic construct.


coder.extrinsicDeclare a function as extrinsic and execute it in MATLAB
coder.ignoreConstPrevent use of constant value of expression for function specializations
coder.ignoreSizePrevent code generator from creating function specializations for constant-size expressions
coder.noImplicitExpansionInFunctionDisable implicit expansion within the specified function in the generated code


Compilation Directive %#codegen

Indicate that a MATLAB function is intended for code generation.

Code Generation for Variable Length Argument Lists

Generate code for varargin and varargout.

Code Generation for Recursive Functions

Use recursive functions in MATLAB code that is intended for code generation.

Force Code Generator to Use Run-Time Recursion

Rewrite your MATLAB code so that the code generator uses run-time recursion instead of compile-time recursion.

Code Generation for Anonymous Functions

Use anonymous functions in MATLAB code intended for code generation.

Code Generation for Nested Functions

Use nested functions in MATLAB code intended for code generation.

Resolution of Function Calls for Code Generation

The code generator uses precedence rules to resolve function calls.

Resolution of File Types on Code Generation Path

The code generator uses precedence rules to resolve file types.

Use MATLAB Engine to Execute a Function Call in Generated Code

If a function is not supported for code generation, declare it as extrinsic to execute in MATLAB.


Nonconstant Index into varargin or varargout in a for-Loop

Force loop unrolling when the code generator cannot determine the value of the index into varargin or varargout.

Avoid Duplicate Functions in Generated Code

Reduce the occurrence of duplicate functions in the generated code.

Output Variable Must Be Assigned Before Run-Time Recursive Call

Troubleshoot output variable assignment for run-time recursion.

Compile-Time Recursion Limit Reached

Troubleshoot compile-time recursion limit error.