NAME
    . - oldvalue

SYNOPSIS
    .  (with no adjacent letters or digits or _ or .)

TYPES
    return	any

DESCRIPTION
    The "old value" is essentially a global variable with identifier "."
    which at top level when directly from a file or keyboard
    is automatically assigned the saved value for a line
    of statements when evaluation of that line is completed and this saved
    value is not null.  A line of statements is normally completed by a
    '\n' not within a block bounded by braces or an expression bounded by
    parentheses.

    Disabling of saving by calling saveval(0) causes lines to return a
    null value and . then becomes in effect a global variable whose
    value may be changed by assignments and operations like ++ and --.

    A null value may be assigned to . by . = null() or free(.).

EXAMPLE
    > saveval(1);
    > a = 2
    > .
	    2
    > . += 3; b = . + 4
    > print ., b
    9 9
    > . += 3; b = . + 4; null()
    > print ., b
    12 16
    > list(a, b, a + b)

    list (3 elements, 3 nonzero):
	    [[0]] = 2
	    [[1]] = 16
	    [[2]] = 18

    > saveval(0)
    > print pop(.), .[[1]]
    2 18

LIMITS
    none

LIBRARY
    none

SEE ALSO
    saveval