/**
* prune()
*
* @return - An abstract syntax tree with less junk in it than the parse tree itself, which
* includes ALL Nonterminals.
* <p>Gross.
* <p>What Nonterminals are "useless" is determined by the String array at the top of
* Parser.java
* <p>WHAT ALL DOES PRUNE DO: 1. Removes USELESS_TERMINALS from our parse tree 2. Removes
* Nonterminals with no children, unless it is a function call with no arguments 3. Remove
* Nonterminals with only one child, pass up the child to parent Nonterminal 4. Combines type
* and * to make a "pointer type", ex. type: int and punctuation: * get combined to type:int*
* 5. Reformats VAR-DECs and FUN_DECs from DECs.
* <p>Productions to clean up: 1. FUN-DEC - done 2. VAR-DEC - done 3. CALL 4. EXPR? 5. PARAMS
*/
public ArrayList<Symbol> prune() {
ArrayList<Symbol> ret = new ArrayList<Symbol>();
if (this instanceof Terminal) {
boolean useless = false;
for (String s : Parser.USELESS_TERMINALS) if (s.equals(data())) useless = true;
if (useless) return ret;
Symbol clone = this.copy();
ret.add(this.copy());
return ret;
}
// Prune our children.
ArrayList<Symbol> prunedChildren = new ArrayList<Symbol>();
for (int i = 0; i < children.size(); i++) {
Symbol child = children.get(i);
prunedChildren.addAll(child.prune());
}
// Combine type and * to make a "pointer type"
for (int i = 0; i < prunedChildren.size(); i++) {
Symbol child = prunedChildren.get(i);
if (child.type().equals("type") && prunedChildren.get(i + 1).data().equals("*")) {
child.setData(child.data() + "*");
prunedChildren.remove(i + 1);
}
}
// AD-HOC FIX: try to associate function names/types with a FUN-DEC,
// rather than dangling as Terminal children inside the DEC node.
// Also try to make all variable declarations part of a VAR-DEC node.
// This includes global variable declarations, vardecs within funcs,
// params, and args. (some of this stuff TODO).
if (type().equals("DEC")) {
// At this point remember: all our children are pruned already.
for (int i = 0; i < prunedChildren.size(); i++) {
Symbol child = prunedChildren.get(i);
//
// CASE 1: DEC --> FUN-DEC
//
if (child.type().equals("FUN-DEC")) {
child.add(0, prunedChildren.remove(i - 2)); // Add the type
child.add(1, prunedChildren.remove(i - 2)); // Add function name
}
}
for (int i = 0; i < prunedChildren.size(); i++) {
Symbol child = prunedChildren.get(i);
//
// CASE 2: DEC --> type (*) identifier ([ integer ]) ;
//
if (type().equals("DEC") && !child.type().equals("FUN-DEC")) {
Nonterminal varDec = new Nonterminal("VAR-DEC", "VAR-DEC");
while (prunedChildren.size() > 0) varDec.add(prunedChildren.remove(i));
prunedChildren.add(varDec);
}
}
}
// AD-HOC FIX: Move around information in PARAM so that the first
// child is always the abbreviated type (type including *, if it's
// there), and the second child is the identifier's name.
else if (type().equals("PARAM*")) {
for (int i = 0; i < prunedChildren.size(); i++) {
Symbol child = prunedChildren.get(i);
if (child.data().equals("[") || child.data().equals("]")) continue;
ret.add(prunedChildren.remove(i--)); // This is SUPER jank. Hahahah!
}
}
// AD-HOC FIX: Move around information in CALL so that identifiers
// appear inside of the CALL node, rather than before.
else if (type().equals("PRIMARY-EXPR")) {
for (int i = 0; i < prunedChildren.size(); i++) {
Symbol child = prunedChildren.get(i);
if (child.type().equals("identifier")) {
// Is the next child a CALL?
if ((i + 1 < prunedChildren.size()) && prunedChildren.get(i + 1).type().equals("CALL")) {
prunedChildren.get(i + 1).add(0, prunedChildren.remove(i));
}
}
}
}
// AD-HOC FIX: Move around information in ARGS so that it more closely
// resembles the structure of VAR-DEC, FUN-DEC, and PARAMS
else if (type().equals("ARGS")) {
for (int i = 0; i < prunedChildren.size(); i++) {
Symbol child = prunedChildren.get(i);
if (child.type().equals("POSTFIX-EXPR")) {
// TODO??
}
}
}
// AD-HOC FIX: Move around information in EXPR and EXPR* so that it is
// clearer what assignment operation we're dealing with. Note that by
// the nature of our grammar, the LHS of the assignop will always be a
// single node.
else if (type().equals("EXPR")) {
if (prunedChildren.size() >= 2 && prunedChildren.get(1).type().equals("ASSIGN-EXPR*")) {
// Move LHS of EXPR* assignment operation into EXPR*,
// and give EXPR* a more appropriate name.
Symbol exprStar = prunedChildren.get(1);
exprStar.add(0, prunedChildren.remove(0));
exprStar.setType("ASSIGN-EXPR");
}
} else if (type().equals("EXPR*")) {
setType("ASSIGN-EXPR*"); // I mean, WTF is an EXPR*, anways?
}
// Nonterminal with no children = useless, automatically, Unless it's a call to a funtion with
// no arguments??
// if ( prunedChildren.size() == 0 )
if (prunedChildren.size() == 0 && !type().equals("ARGS") && !type().equals("OPTIONAL-EXPR"))
return ret;
// If after pruning we have only 1 child, then just pass
// up the child and omit this node. We want to keep the CALL and ARGS nodes though
if (prunedChildren.size() == 1
&& !type().equals("ARGS")
&& !type().equals("PARAMS")
&& !type().equals("CALL")
&& !type().equals("FUN-DEC")
&& // Added FUN-DEC here...not sure why this needs to be here, but it fixes things...
!type().equals("PROGRAM")) {
return prunedChildren;
}
// Check to see if we are useless
boolean useless = true;
for (String s : Parser.USEFUL_NONTERMINALS) if (s.equals(type())) useless = false;
if (useless) {
return prunedChildren;
} else {
Symbol newSym = this.copy();
newSym.setChildren(prunedChildren);
ret.add(newSym);
return ret;
}
}