recursion - Using Alloy functions in a recursive way through transitive closures -

i doing model in alloy represent subset of java language. below have elements of model:

sig method {     id : 1 methodid,     param: lone type,     return: 1 type,     acc: lone accessibility,         b: 1 block }  abstract sig expression {} abstract sig statementexpression extends expression {}  sig methodinvocation extends statementexpression{     pexp: lone primaryexpression,      id_methodinvoked: 1 method,     param: lone type }  sig block {     statements: seq statementexpression }  pred norecursivemethodinvocationcall [] {     no m:method | m in ^getmethodinvokedinsidebody[m] }  fun getmethodinvokedinsidebody [m: method] : method {       (univ.(m.b.statements)).id_methodinvoked } 

the problem block has sequence of statementexpression @ same time recursive calls same method should avoided. thus, thought in solution above.

when try generate corresponding instances following error type:

. name cannot resolved; possible incorrect function/predicate call; perhaps used ( ) when should have used [ ]  cannot correct call fun genericlawsmetamodel/javametamodel_withfield_final/getmethodinvokedinsidebody. parameters m: {genericlawsmetamodel/javametamodel_withfield_final/method} arguments cannot empty. 

still regarding question, tried changing definition predicate norecursivemethodinvocationcall (thus eliminating mentioned function):

pred norecursivemethodinvocationcall [] {     no m:method | m in ^( (univ.(m.b.statements)).id_methodinvoked ) } 

however, new type error occurs:

^ can used binary relation. instead, possible type(s) are: {genericlawsmetamodel/javametamodel_withfield_final/method} 

any clue? want avoid recursive calls same method. in advance,

you misusing transitive closure operator ^. latter applies on binary relations solely, not on functions.

i declare methodinvokedinsidebody field of method , use transitive closure on way did.

hope helps :)

edit:

here example of how transitive closure operator can used in order achieve want achieve:

sig method {     id : 1 methodid,     param: lone type,     return: 1 type,     acc: lone accessibility,         b: 1 block     methodsinvokedinsidebody: set method }  pred norecursivemethodinvocationcall{     no m:method | m in m.^methodsinvokedinsidebody }