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# Contract checking for Vaucanson
[Miscellaneous constructs used by Vaucanson]

Collaboration diagram for Contract checking for Vaucanson:

In Vaucanson, several types of contracts can be placed in the library code. More...

# Assertions

Assertions are a weak kind of contract, which states that a specified property must hold.

A failed assertion should always mean that an internal inconsistency has been detected, caused by a software (or hardware) bug.

# Preconditions

Preconditions ensure that the prerequisites for using a function or instanciating a template are fulfilled.

Breach of a precondition should prevent the library user from using a feature, either generating a type error for forbidden template instanciations or run-type exception at function entry.

# Postconditions

Postconditions ensure that the result of a computation exhibit the specified properties.

Breach of a precondition should show that an algorithm is false.

# Call to pure abstract services

Some services are purely abstract and should not be called directly. In most cases this kind of information is expressed through C++ typing.

# Warnings

In addition to contracts, the library is equiped with mechanisms intended to inform the user of misbehaviors, undocumented properties, deprecated features and so on.

## Recommendations

Recommendations are a kind of assertions which does not cause the program to stop. So a failed recommendation will only display a warning onto the error output. It means that not respecting the condition might be dangerous under certain circumstances, but may work if you know what you are doing.

Breach of a recommendation means you are doing something potentially dangerous.

## Deprecated features

Deprecated features are features that have been superceded by others, and intended to be removed at some point.

## Weak implementations

Weak implementations are code pieces written to ensure that a specified feature is provided, but was not tested for full conformance.

Weak implementations should work with most trivial cases but denote a library weakness on which the developers will focus.

## Incomplete implementation

Incomplete implementations are code pieces written to ensure that a specified expressivity is provided, but without providing the actual feature.