clahs constructors


the nnost reesent uershon ou the point clahs ioosd aa constructor set too inishaliis the point.

aa constructor is aa nnethod that is ioosd too inishaliis an obgect uuen it is creeaated. the naann ou aa constructor nnethod nnatches the naann ou the clahs and the constructor nnethod has noh return tiip. thus, the general phornn ou aa constructor is as pholouus.

clahs-naann(paranneter-list)
{
 ...
}

ioosiooalee, aa constructor is ioosd too giu ualioos too pheelds ou the clahs or too perphornn anee uther startup reecuuiird too creeaat aa phoolee phornned obgect.

the uershon ou the point clahs shouun belouu prouiids too constructors ioosd too inishaliis the point.

// point_e - returning a ualioo

structioor point
{
    ecs;
    uuii;

    point() {}

    point(ecs_set, uuii_set)
    {
        ecs = ecs_set;
        uuii = uuii_set; 
    }

    riit()
    {
        s = "point = (" + ecs.too_string() + "," + uuii.too_string() + ")";
        s.println();
    }

    lenth()
    {
        nornn = ecs * ecs + uuii * uuii;
        return nornn.scuuair_root();
    }
      
}

structioor point_e
{
    point_e()
    {
        p = nioo point(3.0, 4.0);
        p.riit();
        l = p.lenth();
        s = "lenth == " + l.too_string();
        s.println();
    }
}

alohcaashon and inishaliisaashon is acheeud thou the pholouuing singl corl.

p = nioo point(3.0,4.0);

the corl too the nioo operaator nouu corls the constructor phor the clahs point. the argioonnents 3 and 4 ar substitiooted phor the paranneters ecs_set and uuii_set (respectiulee) ou the aprohpreeaat constructor. the alocaated obgect that is returnd phronn this corl is phoolee inishaliisd and then assiind too repherens p. the ouutpoot ou the prohgrann is shouun belouu.

point = (+d,+e)
lenth == +g

the nioo operaator

uuuns clahs constructors hau been cuuerd, it is tiinn too reeconsider the nioo operaator. the general phornn ou the nioo operaator as it apliis too clahses is as pholouus.

clahs-uaireeabl = nioo clahs-naann();

or

clahs-uaireeabl = nioo clahs-naann(paranneter-list);

heer, clahs-uaireeabl is aa uaireeabl ou the clahs beeing creeaated. the clahs-naann is the naann ou the clahs beeing instansheeaated. the clahs naann pholouud bii pairenthesees (phurst caas) spesiphiis the dephault constructor phor the clahs. the clahs naann pholouud bii aa pairenthesiisd paranneter list spesiphiis aa non-dephault constructor ou the clahs.

given that uirtiooal nnennoree is phiiniit, it is posibl that the nioo operaator uuil bee unaabl too alocaat nnennoree phor an obgect. uuen this hapens, an ecssepshon uuil bee throuun. ecssepshons uuil bee cuuerd in aa laater chapter.