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Ada Programming/Pragmas/Pack:3

< Ada Programming‎ | Pragmas

Exact data representation edit

It is important to realize that pragma Pack must not be used to specify the exact representation of a data type, but to help the compiler to improve the efficiency of the generated code.[1] The compiler is free to ignore the pragma, therefore if a specific representation of a type is required, representation clauses should be used instead (record representation clauses, and/or attributes 'Size or 'Component_Size).

Bit-wise operations edit

Although in Ada 83 packed boolean arrays were used for bit-wise operations,[2] since Ada 95 modular types are more adequate for these operations.[3] The argument may be weighed against the advantages of named Boolean array indexes such as Traffic_Lights'(Red => True, others => False), depending on use case.

  1. ↑ Adam Beneschan (2008-01-09). "Pragma Pack vs. Convention C, portability issue?". comp.lang.ada. (Web link). Retrieved on 2008-05-27.
  2. ↑ Software Productivity Consortium (October 1995). Ada 95 Quality and Style Guide, "10.5.7 Packed Boolean Array Shifts"
  3. ↑ Software Productivity Consortium (October 1995). Ada 95 Quality and Style Guide, "10.6.3 Bit Operations on Modular Types"
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