/**
* Returns an Abstraction object resulting from lifting the given expression with captured
* variable set. if <code>f
* x y</code> is an expression with <code>y</code> a captured variable, then it is transformed
* into <code>lambdaXXX
* = \ y -> f x y</code> which can later be used to replace the original expression with <code>
* lambdaXXX y</code>.
*
* @param e
* @param captured
* @return a String object
* @throws SymbolException
*/
private String lift(Expression e, Set captured) throws SymbolException {
if (e instanceof Abstraction) return lift((Abstraction) e, captured);
Abstraction abs = new Abstraction();
/* bind captured variables */
Iterator it = captured.iterator();
while (it.hasNext()) {
LocalBinding lb = (LocalBinding) it.next();
LocalBinding nlb = new LocalBinding(lb.getName());
abs.bind(nlb);
}
/* restore body */
abs.setBody(e);
String newname = "lambda" + counter++;
ns.bind(newname, abs);
return newname;
}
/*
* (non-Javadoc)
*
* @see jaskell.compiler.JaskellVisitor#visit(jaskell.compiler.core.Module)
*/
public Object visit(Namespace a) {
/* set current namespace */
ns = a;
/*
* visit definitions We set an infinite loop to cope with modifications
* introduced by visiting sub expressions. When something is modified -
* through lift - we restart the whole process. TODO : change this to defer
* registering new bindings at end
*/
while (true) {
try {
Iterator it = a.getAllBindings().entrySet().iterator();
while (it.hasNext()) {
Map.Entry entry = (Map.Entry) it.next();
String functionName = (String) entry.getKey();
Expression def = (Expression) entry.getValue();
if (def instanceof Abstraction)
((Abstraction) def).setClassName(ns.getName() + "." + functionName);
log.finest("Analyzing lifting for " + functionName);
lift = false;
entry.setValue((Expression) def.visit(this));
}
break;
} catch (ConcurrentModificationException cmex) {
/* restart the process */
}
}
return a;
}
/**
* This method produces a new Abstraction which is the result of adding captured variables as new
* arguments and bind it in current ns. It returns the name of the bound funciton.
*
* @param a
* @param captured
* @return a String object denoting the name given to this function
* @throws SymbolException
*/
private String lift(Abstraction a, Set captured) throws SymbolException {
Abstraction abs = a;
if (!captured.isEmpty()) {
/* recreate abstraction adding captured variables */
abs = new Abstraction();
/* bind captured variables */
Iterator it = captured.iterator();
while (it.hasNext()) {
LocalBinding lb = (LocalBinding) it.next();
LocalBinding nlb = new LocalBinding(lb.getName());
abs.bind(nlb);
}
/* rebind old variables */
it = a.getBindings().values().iterator();
while (it.hasNext()) {
LocalBinding lb = (LocalBinding) it.next();
LocalBinding nlb = new LocalBinding(lb.getName());
abs.bind(nlb);
}
/* restore body */
abs.setBody(a.getBody());
}
/*
* bind new abstraction in ns if a is an anonymous abstraction - no class
* name - then it is renamed lambdaXXX and bound in namespace. Else, it is
* given a new name and a reference to this new name is stored in substMap.
*/
String newname = "lambda" + counter++;
ns.bind(newname, abs);
abs.setClassName(ns.getName() + "." + newname);
return newname;
}
/*
* If we visit a nested abstraction, we just launch a new lift operation on
* this abstraction using current context as namespace and returns an
* Application object
*
* @see jaskell.compiler.JaskellVisitor#visit(jaskell.compiler.core.Abstraction)
*/
public Object visit(Abstraction a) {
if (!lift) {
/* top level abstractions */
lift = true;
a.setBody((Expression) a.getBody().visit(this));
return a;
}
/* first visit body */
a.setBody((Expression) a.getBody().visit(this));
/* retrieve outer LocalBindings */
Set captured = new HashSet();
CaptureCollector cc = new CaptureCollector(captured);
a.visit(cc);
/* return the newly computed abstraction as an application spine */
String vname;
try {
vname = lift(a, captured);
Expression ex = applyLifted(vname, captured);
ex.setParent(a.getParent());
return ex;
} catch (SymbolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}
}
/** @see jaskell.compiler.JaskellVisitor#visit(Abstraction) */
public Object visit(Abstraction a) {
try {
Type t = a.getType();
if (t != null) return subst.substitute(t);
log.finest("Visiting abstraction : " + a);
Expression body = a.getBody();
/* duplicate bindings map to assign types to variables */
pushContext(a.getBindings());
/* create fresh type variables as type for each bound
* variable */
Iterator it = namesMap.values().iterator();
LinkedList tl = new LinkedList();
while (it.hasNext()) {
LocalBinding name = (LocalBinding) it.next();
Type vt = TypeFactory.freshBinding();
name.setType(vt);
tl.add(vt);
}
Type tv = TypeFactory.freshBinding();
/* create type with all variables for function */
Type ft = Types.fun(tl, tv);
log.finer("In abstraction, setting type to " + ft);
a.setType(ft);
/* analyze body */
Type bt = (Type) body.visit(this);
/* unify return type of function with type of body */
Type ret = tu.unify(PrimitiveType.getReturnType(ft), bt, typeVariablesMap);
TyvarSubstitution tys = new TyvarSubstitution(typeVariablesMap);
tys.visit(a);
log.finer("Done abstraction, setting type from " + ft + " to " + a.getType());
popContext();
return a.getType();
} catch (TypeError te) {
if (te.getLineCol() == null) te.setLineCol(a.getTag("source"));
throw te;
}
}
