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currypackages
currycheck
Commits
d0df9d7a
Commit
d0df9d7a
authored
Dec 14, 2017
by
Michael Hanus
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Support to check equivalence of operations added (combinator <=>)
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9a9fcb48
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README.md
README.md
+1
1
docs/manual.tex
docs/manual.tex
+90
2
examples/equivalent_operations/Ints12.curry
examples/equivalent_operations/Ints12.curry
+13
0
examples/equivalent_operations/README.md
examples/equivalent_operations/README.md
+6
0
examples/equivalent_operations/RevRev.curry
examples/equivalent_operations/RevRev.curry
+9
0
examples/equivalent_operations/SimpleExample.curry
examples/equivalent_operations/SimpleExample.curry
+25
0
examples/equivalent_operations/SortEquiv.curry
examples/equivalent_operations/SortEquiv.curry
+36
0
package.json
package.json
+1
1
src/CurryCheck.curry
src/CurryCheck.curry
+442
105
src/PropertyUsage.curry
src/PropertyUsage.curry
+19
7
No files found.
README.md
View file @
d0df9d7a
...
...
@@ 12,7 +12,7 @@ and, thus, they are also useful to document the code.
The tool can be directly installed by the command
> cpm install
bin
currycheck
> c
y
pm install currycheck
This installs the executable
`currycheck`
in the bin directory of CPM.
...
...
docs/manual.tex
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d0df9d7a
...
...
@@ 548,6 +548,90 @@ sortSatisfiesSpecification :: [Int] > Prop
sortSatisfiesSpecification x = sort x <~> sort'spec x
\end{curry}
\subsection
{
Checking Equivalence of Operations
}
CurryCheck supports also equivalence checks for operations.
Two operations are considered as
\emph
{
equivalent
}
if they
can be replaced by each other in any possible context
without changing the computed values (see
\cite
{
AntoyHanus12PADL
}
for a precise definition).
For instance, the Boolean operations
\begin{curry}
f1 :: Bool > Bool f2 :: Bool > Bool
f1 x = not (not x) f2 x = x
\end{curry}
are equivalent, whereas
\begin{curry}
g1 :: Bool > Bool g2 :: Bool > Bool
g1 False = True g2 x = True
g1 True = True
\end{curry}
are not equivalent:
\code
{
g1 failed
}
has no value but
\code
{
g2 failed
}
evaluates to
\code
{
True
}
.
To check the equivalence of operations, one can use the
property combinator
\code
{
<=>
}
:
\begin{curry}
f1
_
equiv
_
f2 = f1 <=> f2
g1
_
equiv
_
g2 = g1 <=> g2
\end{curry}
CurryCheck transforms such properties into properties
where both operations are compared w.r.t.
\
all partial
values and partial results.
The details are described in an upcoming paper.
It should be noted that CurryCheck can also check
the equivalence of nonterminating operations provided
that they are
\emph
{
productive
}
, i.e., always generate
(outermost) constructors after a finite number of steps
(otherwise, the test of CurryCheck might not terminate).
For instance, CurryCheck reports a counterexample to
the equivalence of the following nonterminating operations:
\begin{curry}
ints1 n = n : ints1 (n+1)
$
\listline
$
ints2 n = n : ints2 (n+2)
 This property will be falsified by CurryCheck:
ints1
_
equiv
_
ints2 = ints1 <=> ints2
\end{curry}
This is done by guessing depthbounds and comparing the results
of both operations up to this depthbound.
Since this might be a long process, CurryCheck supports
a faster comparison of operations when it is known
that they are terminating.
If the name of a test contains the suffix
\code
{
'TERMINATE
}
,
then CurryCheck does not iterate over depthbounds
but evaluates operations completely.
For instance, consider the following definition of
permutation sort (the operations
\code
{
perm
}
and
\code
{
sorted
}
are defined above):
\begin{curry}
psort :: [a] > [a]
psort xs  sorted ys = ys
where ys = perm xs
\end{curry}
A different definition can be obtained by defining
a partial identity on sorted lists:
\begin{curry}
isort :: [a] > [a]
isort xs = idSorted (perm xs)
where idSorted [] = []
idSorted [x] = [x]
idSorted (x:y:ys)  x<=y = x : idSorted (y:ys)
\end{curry}
When checking the equivalence of both operations by
\begin{curry}
psort
_
equiv
_
isort = psort <=> isort
\end{curry}
CurryCheck reports a counter example by the 89th test.
Since both operations are terminating, we can also check
the following property:
\begin{curry}
psort
_
equiv
_
isort'TERMINATE = psort <=> isort
\end{curry}
Now a counter example is found by the 11th test.
\subsection
{
Checking Usage of Specific Operations
}
In addition to testing dynamic properties of programs,
...
...
@@ 567,8 +651,7 @@ Set functions \cite{AntoyHanus09} are used to encapsulate
all nondeterministic results of some function in a set structure.
Hence, for each toplevel function
$
f
$
of arity
$
n
$
,
the corresponding set function can be expressed in Curry
(via operations defined in the module
\code
{
SetFunctions
}
, see Section~
\ref
{
Library:SetFunctions
}
)
(via operations defined in the library
\code
{
SetFunctions
}
)
by the application
\ccode
{
set
$
n
$
$
f
$}
(this application is used
in order to extend the syntax of Curry with a specific notation
for set functions).
...
...
@@ 580,3 +663,8 @@ Hence, CurryCheck reports such unintended uses of set functions.
% LocalWords: CurryCheck
%%% Local Variables:
%%% mode: latex
%%% TeXmaster: "main"
%%% End:
examples/equivalent_operations/Ints12.curry
0 → 100644
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d0df9d7a
 Testing the equivalence of nonterminating operations:
import Nat
import Test.Prop
 Two different infinite lists:
ints1 n = n : ints1 (n+1)
ints2 n = n : ints2 (n+2)
 Falsified by 47th test:
ints1_equiv_ints2 = ints1 <=> ints2
examples/equivalent_operations/README.md
0 → 100644
View file @
d0df9d7a
This directory contains some example for the use
of CurryCheck to check the equivalence of operations.
Since these are examples to test whether CurryCheck
is able to report counterexamples, their test fails
intentionally.
examples/equivalent_operations/RevRev.curry
0 → 100644
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d0df9d7a
import Test.EasyCheck
revrev :: [a] > [a]
revrev xs = reverse (reverse xs)
 Test: is double reverse equivalent to the identity?
 This is not the case if both are applied to the context
 head (... (1:failed))
revrevid'TERMINATE = revrev <=> id
examples/equivalent_operations/SimpleExample.curry
0 → 100644
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d0df9d7a
import Test.Prop
 This is an example which shows the "nonreferentiality" of Curry (according
 to [Bacci et al. PPDP'12]), i.e., it shows that two operations, which
 compute the same values, might compute different results in larger
 contexts:
data AB = A  B
data C = C AB
h A = A
g x = C (h x)
g' A = C A
 The computed result equivalence of g and g' on ground values
 always holds, i.e., g and g' always compute same values:
g_and_g' :: AB > Prop
g_and_g' x = g x <~> g' x
 The contextual equivalence of g and g' does not hold:
g_equiv_g' = g <=> g'
examples/equivalent_operations/SortEquiv.curry
0 → 100644
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d0df9d7a
import Test.Prop
 Permutation sort:
psort :: [a] > [a]
psort xs  sorted ys = ys where ys = perm xs
perm [] = []
perm (x:xs) = ndinsert x (perm xs)
where ndinsert x ys = x : ys
ndinsert x (y:ys) = y : ndinsert x ys
sorted [] = True
sorted [_] = True
sorted (x:y:ys) = x<=y & sorted (y:ys)
 Permutation sort in a different formulation (which is actually not
 equivalent to psort):
isort :: [a] > [a]
isort xs = idSorted (perm xs)
where idSorted [] = []
idSorted [x] = [x]
idSorted (x:y:ys)  x<=y = x : idSorted (y:ys)
 The equality of psort and isort on ground values (which always succeeds
 when tested with CurryCheck):
psort_and_isort x = psort x <~> isort x
 Actually, psort and isort are not equivalent, as can be seen by evaluating
 `head (isort [2,3,1])`.
 Thus, we check the equivalence with CurryCheck:
 In PAKCS, the counter example is reported by the 89th test:
psort_equiv_isort = psort <=> isort
 In PAKCS, the counter example is reported by the 11th test:
psort_equiv_isort'TERMINATE = psort <=> isort
package.json
View file @
d0df9d7a
{
"name"
:
"currycheck"
,
"version"
:
"1.
0.1
"
,
"version"
:
"1.
1.0
"
,
"author"
:
"Michael Hanus <mh@informatik.unikiel.de>"
,
"synopsis"
:
"A tool to support automatic testing of Curry programs"
,
"category"
:
[
"Testing"
],
...
...
src/CurryCheck.curry
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d0df9d7a
This diff is collapsed.
Click to expand it.
src/PropertyUsage.curry
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d0df9d7a
...
...
@@ 3,37 +3,49 @@
 a Curry program.

 @author Michael Hanus
 @version
Augsut
201
6
 @version
December
201
7

module PropertyUsage
( isProperty, isPropType, isPropIOType
( isProperty, isPropType, isPropIOType
, isEquivProperty
, propModule, easyCheckModule, easyCheckExecModule
) where
import AbstractCurry.Types
import AbstractCurry.Select (funcType, resultType)
import AbstractCurry.Select (funcType, resultType
, funcRules
)

 Check whether a function definition is a property,
 i.e., if the result type is `Prop` or `PropIO`.


Check whether a function definition is a property,


i.e., if the result type is `Prop` or `PropIO`.
isProperty :: CFuncDecl > Bool
isProperty = isPropertyType . funcType
where
isPropertyType ct = isPropIOType ct  isPropType (resultType ct)
 Is the type expression the type Test.EasyCheck.Prop?


Is the type expression the type Test.EasyCheck.Prop?
isPropType :: CTypeExpr > Bool
isPropType texp = case texp of
CTCons (mn,tc) [] > tc == "Prop" && isCheckModule mn
_ > False
 Is the type expression the type Test.EasyCheck.PropIO?


Is the type expression the type Test.EasyCheck.PropIO?
isPropIOType :: CTypeExpr > Bool
isPropIOType texp = case texp of
CTCons (mn,tc) [] > tc == "PropIO" && isCheckModule mn
_ > False
 Check whether a function definition is an equivalence property, i.e.,
 has the form `test = f1 <=> f2`. If yes, returns both operations,
 otherwise `Nothing` is returned.
isEquivProperty :: CFuncDecl > Maybe (QName,QName)
isEquivProperty fdecl =
case funcRules fdecl of
[CRule []
(CSimpleRhs (CApply (CApply (CSymbol prop) (CSymbol f1)) (CSymbol f2)) [])] > if isEquivSymbol prop then Just (f1,f2) else Nothing
_ > Nothing
where
isEquivSymbol (qn,mn) = isCheckModule qn && mn=="<=>"
 Is the module name Test.Prop or Test.EasyCheck?
isCheckModule :: String > Bool
isCheckModule mn = mn == propModule  mn == easyCheckModule
...
...
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