/**
* 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;
}
/**
* This method produces an Expression from an arbitrary Abstraction object which is applied to a
* list of Variables referencing captured bindings.
*
* @param a an Abstraction object to partially apply
* @param captured
* @return
*/
private Expression applyLifted(String s, Set captured) {
if (captured.isEmpty()) return new Variable(s);
Application app = new Application();
app.setFunction(new Variable(s));
/* bind captured variables */
Iterator it = captured.iterator();
while (it.hasNext()) {
LocalBinding lb = (LocalBinding) it.next();
app.addArgument(new Variable(lb.getName()));
}
return app;
}
/**
* 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;
}
/** @see jaskell.compiler.JaskellVisitor#visit(Alternative) */
public Object visit(Alternative a) {
try {
Type tex = (Type) a.getExpression().visit(this);
log.finer("In alternative, type of expression " + a.getExpression() + " is " + tex);
/* set type of bound variable */
LocalBinding lb = a.getBinding();
if (lb != null) lb.setType(tex);
/* visit type of alternatives */
Iterator it = a.getChoices();
Type ptype = tex;
Type btype = null;
while (it.hasNext()) {
Map.Entry entry = (Map.Entry) it.next();
/* checkt type of pattern */
Type pt = (Type) ((Pattern) entry.getKey()).visit(this);
if (ptype == null) ptype = pt;
else ptype = tu.unify(pt, ptype, typeVariablesMap);
log.finer("In alternative, unifying pattern type " + pt + " to " + ptype);
Expression expr = (Expression) entry.getValue();
/* check type of body */
Type bt = (Type) expr.visit(this);
// /* apply substitution with type variables from pattern */
// TypeSubstitution ts = new TypeSubstitution(typeVariablesMap);
// expr.visit(ts);
if (btype == null) btype = bt;
else btype = tu.unify(bt, btype, typeVariablesMap);
log.finer("In alternative, unifying body type " + bt + " to " + btype);
}
/* visit default choice */
Type deft = (Type) a.getWildcard().visit(this);
a.setType(btype);
return btype;
} catch (TypeError te) {
if (te.getLineCol() == null) te.setLineCol(a.getTag("source"));
throw te;
}
}
/** @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;
}
}
/** @see jaskell.compiler.JaskellVisitor#visit(LocalBinding) */
public Object visit(LocalBinding a) {
return a.getType();
}
