compilers-cw2/task3/asts.java

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// Do not modify the code below except for replacing the "..."! Don't
// add anything (including "public" declarations), don't remove
// anything (including "public" declarations). Don't wrap it in a
// package, don't make it an innner class of some other class. If
// your IDE suggsts to change anything below, ignore your IDE. You are
// welcome to add new classes! Please put them into separate files.
import java.util.List;
class Program { // Used in Tasks 1, 2, 3.
// Leaves in the accumulator what running the first declaration leaves in the accumulator.
public List <Declaration> decls;
public Program ( List <Declaration> _decls ) {
assert ( _decls.size () > 0 ); // ensures that we have at least one declaration the
// first element in decls is the the procedure executed
// at startup. We assume that this initial procedure takes
// 0 arguments. NOTE: the entry procedure does NOT have
// have to be called "main". It can have ANY valid identifier
// as name.
assert ( _decls.get ( 0 ).numOfArgs == 0 ); // ensures that the first declaration takes
// 0 arguments.
decls = _decls; } }
class Declaration { // Used in Tasks 1, 2, 3.
public String id;
public int numOfArgs; // Used for computing the size of the AR.
public Exp body;
public Declaration ( String _id, int _numOfargs, Exp _body ) {
assert ( _numOfargs >= 0 );
id = _id;
numOfArgs = _numOfargs;
body = _body; } }
abstract class Exp {} // Used in Tasks 1, 2, 3.
class IntLiteral extends Exp { // Used in Tasks 1, 2, 3.
// Leaves n in the accumulator.
public int n;
IntLiteral ( int _n ) { n = _n; } }
class Variable extends Exp { // Used in Tasks 1, 2, 3.
// Leaves the content of the variables x in the accumulator. Note
// that the integer x represents the OFFSET of the variable relative
// to the encompassing procedure declaration (which is used by the
// code generator to compute, at compile time, the place, relative
// to the frame pointer, where the variable is stored at
// run-time). It does NOT hold the values the variable takes at
// run-time. E.g. in
//
// def f ( a, b, c, d ) = ...
//
// the variable a has offset 1, b has offset 2, c has 3 and d has
// 4. There are no other offsets for this procedure.
public int x;
public Variable ( int _x ) {
assert ( _x > 0 ); // ensures that 1 is the smallest possible offset.
x = _x; } }
class If extends Exp { // Used in Tasks 1, 2, 3.
// If the comparison is true, executes the thenBody.
// Otherwise the elseBody is executed.
public Exp l;
public Comp comp;
public Exp r;
public Exp thenBody;
public Exp elseBody;
public If ( Exp _l, Comp _comp, Exp _r, Exp _thenBody, Exp _elseBody ) {
l = _l;
comp = _comp;
r = _r;
thenBody = _thenBody;
elseBody = _elseBody; } }
class Binexp extends Exp { // Used in Tasks 1, 2, 3.
// Evaluates l, then r, and applies binop to both.
public Exp l;
public Binop binop;
public Exp r;
public Binexp ( Exp _l, Binop _binop, Exp _r ) {
l = _l;
binop = _binop;
r = _r; } }
class Invoke extends Exp { // Used in Tasks 1, 2, 3.
// Evaluates the arguments right-to-left. Then calls the procedure name with
// these arguments.
public String name;
public List<Exp> args;
public Invoke ( String _name, List<Exp> _args ) {
name = _name;
args = _args; } }
class While extends Exp { // Used in Tasks 2, 3.
// Implements the standard while-loop,
// Can return anything in accumulator
public Exp l;
public Comp comp;
public Exp r;
public Exp body;
public While ( Exp _l, Comp _comp, Exp _r, Exp _body ) {
l = _l;
comp = _comp;
r = _r;
body = _body; } }
class RepeatUntil extends Exp { // Used in Tasks 2, 3.
// Implements the standard repeat-unitl loop,
// Can return anything in accumulator.
public Exp body;
public Exp l;
public Comp comp;
public Exp r;
public RepeatUntil ( Exp _body, Exp _l, Comp _comp, Exp _r ) {
body = _body;
l = _l;
comp = _comp;
r = _r; } }
class Assign extends Exp { // Used in Tasks 2, 3.
// Evaluates the right-hand side e, and stores the result
// Can return anything in accumulator.
public int x;
public Exp e;
public Assign ( int _x, Exp _e ) {
assert ( _x > 0 );
x = _x;
e = _e; } }
class Seq extends Exp { // Used in Tasks 2, 3.
// Runs l first, then r.
// Returns the result of r in the accumulator.
public Exp l;
public Exp r;
public Seq ( Exp _l, Exp _r ) {
l = _l;
r = _r; } }
class Skip extends Exp { // Used in Tasks 2, 3.
// Does nothing.
// Can return anything in accumulator.
public Skip () {} }
class Break extends Exp { // Used in Task 3 only.
// Exits the nearest enclosing loop. Leaves
// Can return anything in accumulator.
public Break () {} }
class Continue extends Exp { // Used in Task 3 only.
// Abandons the current iteration of the nearest enclosing
// loop, jumping straight to the checking of the conditional.
// Can return anything in accumulator.
public Continue () {} }
abstract class Comp {} // Used in Tasks 1, 2, 3.
class Less extends Comp { // Used in Tasks 2, 3.
public Less () {} }
class LessEq extends Comp { // Used in Tasks 2, 3.
public LessEq () {} }
class Equals extends Comp { // Used in Tasks 1, 2, 3.
public Equals () {} }
class Greater extends Comp { // Used in Tasks 2, 3.
public Greater () {} }
class GreaterEq extends Comp { // Used in Tasks 2, 3.
public GreaterEq () {} }
abstract class Binop {}
class Plus extends Binop { // Used in Tasks 1, 2, 3.
public Plus () {} }
class Minus extends Binop { // Used in Tasks 1, 2, 3.
public Minus () {} }
class Times extends Binop { // Used in Tasks 2, 3.
public Times () {} }
class Div extends Binop { // Used in Task 3 only.
public Div () {} }