| Commit message (Collapse) | Author | Age |
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class are now
automatically static, and fields are no longer allowed to be declared there. Stated
differently, all heap state must now be declared inside an explicitly declared class,
and functions and methods declared outside any class can be viewed as belonging to
the module. The motivating benefit of this change is to no longer need the 'static'
keyword when declaring a module of functions and methods.
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Now, loops that may possibly
do an infinite number of iterations (that is, loops marked with 'decreases *') and calls to methods
marked with 'decreases *' are allowed only in methods that themselves are marked with 'decreases *'. As
before, ghost loops and ghost methods are not allowed to be marked with 'decreases *'.
Previously, 'decreases *' was allowed on a method only if the method was tail recursive;
this is no longer so. Note, however, that if the method is not tail recursive and engages
in infinite recursion, then it will eventually run out of stack space.
Previously, a 'decreases *' was not inherited in a refining module; this is no longer so.
That is, 'decreases *' is now inherited. To refine a possibly non-terminating method
or loop, the refining version simply provides a decreases clause that does not mention '*'.
Note that if the refined method is not recursive, it still needs to have _some_ decreases
clause in order not to inherit the 'decreases *' from the refined method, but the expression
stated in the decreases clause can be arbitrary (for example, one can write 'decreases true'
or 'decreases 7' or 'decreases x' for some 'x' in scope).
Note, in the new design, a method needs to be declared with 'decreases *' if
it may recurse forever _or_ if it contains a possibly infinite loop.
Note that the absence of 'decreases *' on a loop does not mean the loop will
terminate, but it does mean that the loop will iterate a finite number of times
(the subtle distinction here is that a loop without a 'decreases *' is allowed
to contain a nested loop that has a 'decreases *' -- provided the enclosing
method is also declared with 'decreases *', as previously mentioned).
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* The reads clause now needs to be self framing.
* The requires clause now needs to be framed by the reads clause.
* There are one-shot lambdas, with a single arrow, but they will probably be
removed.
* There is a {:heapQuantifier} attribute to quantifiers, but they will
probably be removed.
* Add smart handling of type variables
* Add < and > for datatype & type parameter
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(previously undetected) specification bug in the test suite.
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reads clause followed by the list of parameters
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codatatypes would then be sound
Dafny: added special case to allow equality comparison against parameter-less datatype values
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body-less functions/methods
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previously was an alternative syntax
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* started rewriting parsing of qualified identifiers in expressions
* annoyingly, had to introduce AST nodes for concrete syntax
* previous syntax for invoking datatype constructors: #List.Cons(h, t)
new syntax: List.Cons(h, t)
or, if only one datatype has a constructor named Cons: Cons(h, t)
* Removed type parameters for datatype constructors from the grammar
* Helped Test/VSI-Benchmarks/b4.dfy along with a couple of assertions (previously, its proving performance was highly varied)
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* Big change: Add type and allocatedness information everywhere in the Boogie translation. This not only fixes some potential soundness problems (see Test/dafny1/TypeAntecedents.dfy), but it also gives more information about the program. On the downside, it also requires discharging more antecedents in order to use some axioms. Another downside is that overall performance has gone down (however, this may be just an indirect consequence of the change, as it was in one investigated case).
* Increase the applicability of function axioms (extending the coarse-grain function/module height mechanism used as an antecedent of function axioms). (Internally, this uses the new canCall mechanism.)
* Extend language with "allocated( Expr )" expressions, which for any type of expression "Expr" says that "Expr" is allocated and has the expected type.
* More details error messages about ill-defined expressions (internally, by using CheckWellformedness instead of "assert IsTotal")
* Add axioms about idempotence of set union and intersection
* The compiler does not support (the experimental feature) coupling invariants, so generate error if the compiler ever gets one
* In the implementation, combine common behavior of MatchCaseStmt and MatchCaseExpr into a superclass MatchCase
* Fixed error in translation of while(*)
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of TOP elements; this reduces the need for manually supplied decreases clauses (see the Outer/Inner example in Test/dafny0/Termination.dfy and the Substitute/SubstSeq example in Test/dafny1/Substitution.dfy).
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* For every loop decreases clause N, generate a free loop invariant N <= N0, where N0 is the value of N just before the loop.
* Added Test/dafny1/KatzManna.dfy, which contains the 3 programs (and their termination annotations) from the Katz and Manna 1975 paper "A closer look at termination" (which benefits from the feature above).
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* Improved design and implementation of SplitExpr
* Fixed some tests in dafny0/Use.dfy
* Added test case (in dafny0/Termination.dfy) to test the recent strengthening of set axioms
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clauses (for loop guard A!=B and for loop guards with multiple conjuncts)
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bodies) match expressions.
Addressed a couple of todos, including checking the well-formedness of quantifiers and if-then-else expressions in function bodies.
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variables, if they were not already local variables.
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qunyanm
Dan Rosén
Unknown
Rustan Leino