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Standards Wording Idioms
sdutoit edited this page May 15, 2012
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This is a list of some common idioms in the standard that should be used to specify certain cases, and corresponding anti-idioms that should not be used.
When you are writing proposals for changes to the C++ standard, please try to follow these idioms. If you notice an anti-idiom in the current C++ standards draft, please [submit an editorial issue](How to submit an editorial issue).
| Case | Idiom(s) | Anti-idiom(s) | Example |
|---|---|---|---|
|
Normative
requirement Use this idiom when specifying something we require a conforming implementation to do. |
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"Unless it is a bit-field, a most derived object shall have a non-zero size" |
|
Normative encouragement Use this idiom when specifying something we would prefer, but do not require, implementations to do. |
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"Implementations should ensure that all unblocked threads eventually make progress" |
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Complicated conditional
cases Use this idiom when you are enumerating a set of possibilities, and stating requirements under those possibilities. |
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"If E1 is an lvalue, then E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue; otherwise, it is a prvalue." |
- Variations on "ill-formed"
Rules for the overall structure and form of ISO standards is provided by the ISO Directives, Part 2. This covers rules common to all ISO documents, such as the meaning of should and shall) above, and the referencing of other standards documents.