NAME
    newerror - create or recall a described error-value

SYNOPSIS
    newerror([str])

TYPES
    str		string

    return	error-value

DESCRIPTION
    If str is not "" and has not earlier been used as an argument for
    this function, newerror(str) creates a new described error-value so
    that any future use of newerror(str) with the same str will return
    the same error-value.

    If x = newerror(str), both strerror(x) and strerror(iserro(x)) will
    return str and iserror(x) will return the error code value of the
    new error.

    The null cases newerror() and newerror("") are equivalent to
    newerror("???").

EXAMPLE
    Note that by default, errmax() is 0 so unless errmax() is
    increased you will get:

    > ba = newerror("curds n' whey");
    Error 20000 caused errcount to exceed errmax

    > errmax(errcount()+5)
	    0
    > e1 = newerror("triangle side length <= 0")
    > iserror(e1)
	    20000
    > error(20000)
	    Error 20000
    > strerror(error(20000))
	    "triangle side length <= 0"
    > strerror(e1);
	    "triangle side length <= 0"
    > strerror(error(iserror(e1)))
	    "triangle side length <= 0"

    > define area(a,b,c) {
    >>	local s;
    >>	if (!(a > 0) || !(b > 0) || !(c > 0)) return e1;
    >>	s = (a + b + c)/2;
    >>	if (s <= a || s <= b || s <= c) return newerror("Non-triangle sides");
    >>	return sqrt(s * (s - a) * (s - b) * (s - c));
    >> }
    "area" defined

    > A = area(8,2,5);
    > if (iserror(A)) print strerror(A) : ":", iserror(A);
    Non-triangle sides: 20001

    > A = area(-3,4,5)
    > if (iserror(A)) print strerror(A) : ":", iserror(A);
    triangle side length <= 0: 20000

LIMITS
    The number of new described error-values is not to exceed 12767.

LIBRARY
    none

SEE ALSO
    errmax, errcount, error, strerror, iserror, errno, errorcodes