Input is read interactively and checked against conditions specified
by the arguments what, lower, upper and
answer.in. If the input does not satisfy all the conditions,
an appropriate error message is produced and the user is prompted
to provide input. This process is repeated until a valid input value
is entered.
read.and.check(message = "", what = numeric(), lower, upper, answer.in,
default)message displayed before prompting for user input.
the type of what gives the type of data to be read.
lower limit of input, for numeric input only.
upper limit of input, for numeric input only.
the input must correspond to one of the elements of the
vector answer.in, if supplied.
value assumed if user enters a blank line.
The value of the valid input. When the default argument is
specified, a blank line is accepted as valid input and in this case
read.and.check returns the value of default.