Task: Test integerness





Java: import java.math.BigDecimal;
import java.util.List;

public class TestIntegerness {
    private static boolean isLong(double d) {
        return isLong(d, 0.0);
    }

    private static boolean isLong(double d, double tolerance) {
        return (d - Math.floor(d)) <= tolerance || (Math.ceil(d) - d) <= tolerance;
    }

    @SuppressWarnings("ResultOfMethodCallIgnored")
    private static boolean isBigInteger(BigDecimal bd) {
        try {
            bd.toBigIntegerExact();
            return true;
        } catch (ArithmeticException ex) {
            return false;
        }
    }

    private static class Rational {
        long num;
        long denom;

        Rational(int num, int denom) {
            this.num = num;
            this.denom = denom;
        }

        boolean isLong() {
            return num % denom == 0;
        }

        @Override
        public String toString() {
            return String.format("%s/%s", num, denom);
        }
    }

    private static class Complex {
        double real;
        double imag;

        Complex(double real, double imag) {
            this.real = real;
            this.imag = imag;
        }

        boolean isLong() {
            return TestIntegerness.isLong(real) && imag == 0.0;
        }

        @Override
        public String toString() {
            if (imag >= 0.0) {
                return String.format("%s + %si", real, imag);
            }
            return String.format("%s - %si", real, imag);
        }
    }

    public static void main(String[] args) {
        List<Double> da = List.of(25.000000, 24.999999, 25.000100);
        for (Double d : da) {
            boolean exact = isLong(d);
            System.out.printf("%.6f is %s integer%n", d, exact ? "an" : "not an");
        }
        System.out.println();

        double tolerance = 0.00001;
        System.out.printf("With a tolerance of %.5f:%n", tolerance);
        for (Double d : da) {
            boolean fuzzy = isLong(d, tolerance);
            System.out.printf("%.6f is %s integer%n", d, fuzzy ? "an" : "not an");
        }
        System.out.println();

        List<Double> fa = List.of(-2.1e120, -5e-2, Double.NaN, Double.POSITIVE_INFINITY);
        for (Double f : fa) {
            boolean exact = !f.isNaN() && !f.isInfinite() && isBigInteger(new BigDecimal(f.toString()));
            System.out.printf("%s is %s integer%n", f, exact ? "an" : "not an");
        }
        System.out.println();

        List<Complex> ca = List.of(new Complex(5.0, 0.0), new Complex(5.0, -5.0));
        for (Complex c : ca) {
            boolean exact = c.isLong();
            System.out.printf("%s is %s integer%n", c, exact ? "an" : "not an");
        }
        System.out.println();

        List<Rational> ra = List.of(new Rational(24, 8), new Rational(-5, 1), new Rational(17, 2));
        for (Rational r : ra) {
            boolean exact = r.isLong();
            System.out.printf("%s is %s integer%n", r, exact ? "an" : "not an");
        }
    }
}





COBOL: IDENTIFICATION DIVISION.
PROGRAM-ID. INTEGERNESS-PROGRAM.
DATA DIVISION.
WORKING-STORAGE SECTION.
01  INTEGERS-OR-ARE-THEY.
    05 POSSIBLE-INTEGER PIC S9(9)V9(9).
    05 DEFINITE-INTEGER PIC S9(9).
01  COMPLEX-NUMBER.
    05 REAL-PART        PIC S9(9)V9(9).
    05 IMAGINARY-PART   PIC S9(9)V9(9).
PROCEDURE DIVISION.
TEST-PARAGRAPH.
    MOVE ZERO TO IMAGINARY-PART.
    DIVIDE -28 BY 7 GIVING POSSIBLE-INTEGER.
    PERFORM INTEGER-PARAGRAPH.
    DIVIDE 28 BY 18 GIVING POSSIBLE-INTEGER.
    PERFORM INTEGER-PARAGRAPH.
    DIVIDE 3 BY 10000000000 GIVING POSSIBLE-INTEGER.
    PERFORM INTEGER-PARAGRAPH.
TEST-COMPLEX-PARAGRAPH.
    MOVE ZERO TO REAL-PART.
    MOVE 1 TO IMAGINARY-PART.
    MOVE REAL-PART TO POSSIBLE-INTEGER.
    PERFORM INTEGER-PARAGRAPH.
    STOP RUN.
INTEGER-PARAGRAPH.
    IF IMAGINARY-PART IS EQUAL TO ZERO THEN PERFORM REAL-PARAGRAPH,
    ELSE PERFORM COMPLEX-PARAGRAPH.
REAL-PARAGRAPH.
    MOVE POSSIBLE-INTEGER TO DEFINITE-INTEGER.
    IF DEFINITE-INTEGER IS EQUAL TO POSSIBLE-INTEGER
    THEN DISPLAY POSSIBLE-INTEGER ' IS AN INTEGER.',
    ELSE DISPLAY POSSIBLE-INTEGER ' IS NOT AN INTEGER.'.
COMPLEX-PARAGRAPH.
    DISPLAY REAL-PART '+' IMAGINARY-PART 'i IS NOT AN INTEGER.'.