ex-21-2

这是一个wmlscript的源代码程序

/*
 * WMLScript backend for calculator example.
 */

/*
 * Add a digit to the number currently being entered, and update display.
 */
extern function digit (d)
{
    /* Read the current number as a string from the browser context. */
    var number = WMLBrowser.getVar ("number");

    /* Add digit to number. (Note that the variable 'number' actually
     * contains a string at this point, so this concatenates strings.) */
    number += d;

    /* Set browser variables and refresh the display. */
    WMLBrowser.setVar ("number", number);
    set_display (Lang.parseFloat ("0" + number));
}

/*
 * Add a decimal point to the number currently being entered.
 */
extern function point (  )
{
    /* Read the current number as a string from the browser context. */
    var number = WMLBrowser.getVar ("number");

    /* Ignore the key if there's already a decimal point. */
    if (String.find (number, '.') >= 0)
        return;

    /* Add a decimal point to the number. */
    number += '.';

    /* Set browser variables and refresh the display. */
    WMLBrowser.setVar ("number", number);
    set_display (Lang.parseFloat ("0" + number));
}

/*
 * Handle an operator key: perform the last operation and store this
 * operator until the next number has been entered.
 */
extern function op (op)
{
    /* Fetch the register and convert to floating point. */
    var register = Lang.parseFloat (WMLBrowser.getVar ("register"));

    /* Fetch the number and convert to floating point. */
    var number = Lang.parseFloat (WMLBrowser.getVar ("display"));

    /* Fetch the last operator key. */
    var lastop = WMLBrowser.getVar ("lastop");

    /* Work out what operation needs to be performed and perform it. */
    if (lastop == 'add')
        register += number;
    else if (lastop == 'sub')
        register -= number;
    else if (lastop == 'mul')
        register *= number;
    else if (lastop == 'div')
        register /= number;
    else
        register = number;

    /* Store the new operator for next time. */
    WMLBrowser.setVar ("lastop", op);

    /* Clear the number so we can enter a new one. */
    WMLBrowser.setVar ("number", "");

    /* Both the display and the register are the result of the operation. */
    WMLBrowser.setVar ("register", String.toString (register));
    set_display (register);
}

/*
 * Set the display browser variable and refresh the display.
 */
function set_display (display)
{
    /* Handle an invalid calculation result. */
    if (!isvalid display)
        display = "(error)";

    /* Set the browser variable. */
    WMLBrowser.setVar ("display", display);

    /* Refresh the display. */
    WMLBrowser.refresh (  );
}