/**
* Add an if clause to a (potentially) pre-existing else clause. The else clase can be null, or
* can be an if expression.
*/
private Expr addIfClause(IfClause c, Expr elsePart) {
GeneratorClause g = c.getTestClause();
if (g.getBind().size() > 0) {
// if binds <- expr then body else elsePart end desugars to
// __cond(expr, fn (binds) => body, elsePart)
ArrayList<Expr> args = new ArrayList<Expr>(3);
args.add(g.getInit());
args.add(bindsAndBody(g, c.getBody()));
if (elsePart != null) args.add(thunk(elsePart));
return (Expr)
recur(
ExprFactory.make_RewriteFnApp(
NodeUtil.getSpan(c),
COND_NAME,
ExprFactory.makeTupleExpr(NodeUtil.getSpan(c), args)));
}
// if expr then body else elsePart end is preserved
// (but we replace elif chains by nesting).
if (elsePart == null) {
return (Expr) super.forIf(ExprFactory.makeIf(NodeUtil.getSpan(c), c));
} else {
return (Expr)
super.forIf(ExprFactory.makeIf(NodeUtil.getSpan(c), c, ExprFactory.makeBlock(elsePart)));
}
}
/** Given generalized if expression, desugar into __cond calls (binding) where required. */
@Override
public Node forIf(If i) {
List<IfClause> clauses = i.getClauses();
int n = clauses.size();
if (n <= 0) bug(i, "if with no clauses!");
for (IfClause c : clauses) {
if (c.getTestClause().getBind().size() == 0) continue;
// If we get here we have a generalized if.
// Desugar it into nested ifs and calls.
// Then return the desugared result.
Expr result = null;
if (i.getElseClause().isSome()) {
result = i.getElseClause().unwrap();
}
// Traverse each clause and desugar it into an if or a __cond as appropriate.
for (--n; n >= 0; --n) {
result = addIfClause(clauses.get(n), result);
}
return result;
}
// If we get here, it's not a generalized if. Just recur.
return super.forIf(i);
}
