D.ershane Solutions Ddili.org

Floating Point Types

  1. Replacing float with double produces an outcome that is surprising in a different way:
    // ...
    
        double result = 0;
    
    // ...
    
        if (result == 1) {
            writeln("As expected: 1");
    
        } else {
            writeln("DIFFERENT: ", result);
        }
    

    Although the value fails the result == 1 comparison, it is still printed as 1:

    DIFFERENT: 1
    

    That surprising outcome is related to the way floating point values are formatted for printing. A more accurate approximation of the value can be seen when the value is printed with more digits after the decimal point. (We will see formatted output in a later chapter.):

            writefln("DIFFERENT: %.20f", result);
    
    DIFFERENT: 1.00000000000000066613
    
  2. Replacing the three ints with three doubles is sufficient:
            double first;
            double second;
    
            // ...
    
            double result;
    
  3. The following program demonstrates how much more complicated it would become if more than five variables were needed:
    import std.stdio;
    
    void main() {
        double value_1;
        double value_2;
        double value_3;
        double value_4;
        double value_5;
    
        write("Value 1: ");
        readf(" %s", &value_1);
        write("Value 2: ");
        readf(" %s", &value_2);
        write("Value 3: ");
        readf(" %s", &value_3);
        write("Value 4: ");
        readf(" %s", &value_4);
        write("Value 5: ");
        readf(" %s", &value_5);
    
        writeln("Twice the values:");
        writeln(value_1 * 2);
        writeln(value_2 * 2);
        writeln(value_3 * 2);
        writeln(value_4 * 2);
        writeln(value_5 * 2);
    
        writeln("One fifth the values:");
        writeln(value_1 / 5);
        writeln(value_2 / 5);
        writeln(value_3 / 5);
        writeln(value_4 / 5);
        writeln(value_5 / 5);
    }