himl_0008: MATLAB code relational operator data types

R2026b

Use the same data type for left and right operands of relational operators

Usage: High-Integrity System Modeling

Guideline ID: himl_0008

Rules

himl_0008: MATLAB® code relational operator data types

For MATLAB code with relational operators, use the same data type for the left and right operands.

Rationale

  • Prevent implicit casts

  • Prevent unexpected results

Verification

Check usage of relational operators in MATLAB Function blocks (Simulink Check)

Example — Correct

  • myBool == true
myInt8 == int8(1)

Example — Incorrect

  • myBool == 1
myInt8 == true
myInt8 == 1
myInt8 == int16(1)
myEnum1.EnumVal == int32(1)

Tips

  • If the two operands have different data types, MATLAB will promote both operands to a common data type. This can lead to unexpected results.

Industry Standards

  • DO-331, Section MB.6.3.1.g 'Algorithms are accurate'

  • DO-331, Section MB.6.3.2.g 'Algorithms are accurate'

  • IEC 61508-3, Table A.3 (2) 'Strongly typed programming language'

  • EC 61508-3, Table A.3 (3) 'Language subset'

  • IEC 62304, 5.5.3 - Software Unit acceptance criteria

  • ISO 26262-6, Table 1(1b) 'Use of language subsets'

  • ISO 26262-6, Table 1(1c) 'Enforcement of strong typing'

  • ISO 26262-6, Table 6 (1g) 'No implicit type conversions'

  • EN 50128, Table A.4 (8) 'Strongly Typed Programming Language'

  • EN 50128, Table A.4 (11) 'Language Subset'

  • EN 50657, Table A.4 (8) 'Strongly Typed Programming Language'

  • EN 50657, Table A.4 (11) 'Language Subset'

Version History

Introduced in R2014a

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See Also