/** Our internal representation of a IfZero expr * in the F0 language. * See http://www.radford.edu/itec380/2024spring-ibarland/Project * * @author Ian Barland * @version 2024.Apr.03 */ public record IfZero(Expr test, Expr thenAns, Expr elseAns) implements Expr { static final String START_TOKEN = "if"; static final String CONT_TOKEN1 = "equinox"; static final String CONT_TOKEN3 = ":"; @Override public String toString() { return START_TOKEN + " " + this.test.toString() + " " + CONT_TOKEN1 + " " + this.thenAns.toString() + " " + CONT_TOKEN3 + " " + this.elseAns.toString() ; } /** “@Override” {@link Expr#parse} */ public static IfZero parse( java.util.Scanner s, String punctuation ) { UtilIan.verifyToken( UtilIan.nextSplittingBy(s,punctuation), START_TOKEN ); // consume&verify the "if" // NOTE: recur with `Expr.parse` -- not `parse` = `IfZero.parse` which is NOT what we want! Expr theTest = Expr.parse(s,punctuation); UtilIan.verifyToken( UtilIan.nextSplittingBy(s,punctuation), CONT_TOKEN1 ); // consume&verify the "equinox" Expr theThenAnswer = Expr.parse(s,punctuation); UtilIan.verifyToken( UtilIan.nextSplittingBy(s,punctuation), CONT_TOKEN3 ); // consume&verify the ":" Expr theElseAnswer = Expr.parse(s,punctuation); return new IfZero(theTest,theThenAnswer,theElseAnswer); } static final double EPSILON = 1e-10; @Override public Value eval() { if ( Math.abs(((Num)(this.test.eval())).doubleValue()) < EPSILON ) { return this.thenAns.eval(); } else { return this.elseAns.eval(); } } }