Laboratoire de l'Informatique et du Parallélisme » Pobyso

r"""

Some small tools needed to manipulate lists of rational numbers.

AUTHORS:

- S.T. (2013-04): initial version

Examples:

    TODO

"""

print "sageRationalOperations loading..."

def sro_denominators(rationalList = None):

    """

    Compute the list of the denominators of a rational numbers list.

    """

    # No argument.

    if rationalList is None:

        raise TypeError('numerators takes a list of rationals.')

    try:

        listLength = len(rationalList)

    except Exception:

        print "denominators:", rationalList, \

                "does not understand the len() function."

        return []

    if listLength == 0:

        return []

    if listLength == 1:

        try:

            return [QQ(rationalList[0]).denominator()]

        except Exception:

            print "denominators:", rationalList[0], \

                    "has no \"denominator()\" member." 

            return []

    denominatorsList = []    

    for i in xrange(listLength):

        try:

            denominatorsList.append(QQ(rationalList[i]).denominator())

        except Exception:

            print "denominators:", rationalList[i], \

                    "has no \"denominator()\" member." 

            return []

    return denominatorsList

# End sro_denominators

def sro_lcmm(rationalList = None):

    """ 

    Compute the lcm of an sequence (list, tuple) of rational numbers.

    In fact, we can (should and do) use lcm instead: it accepts a list argument.

    Kept here has a model for this kind of functions.

    """

    # No argument.

    if rationalList is None:

        raise TypeError('lcmm takes a list of rationals')

    # Try the len function.

    try:

        listLength = len(rationalList)

    except Exception:

        print "lcmm:", rationalList, "does not understand the len() function."

        return(0)

    # An empty list: return 0

    if listLength == 0:

        return(0)

    # Only one element, return it, wahtever it is.

    if listLength == 1:

        return(rationalList[0])

    try:

        return(reduce(lcm, rationalList))

    except Exception:

        print "Exception raised in lcmm!"

        return(0)

# End sro_lcmm

def sro_numerators(rationalList = None):

    """

    Compute the list of the numerators of a rational numbers list.

    """

    # No argument.

    if rationalList is None:

        raise TypeError('numerators takes a list of rationals.')

    try:

        listLength = len(rationalList)

    except Exception:

        print "numerators:", rationalList, \

                "does not understand the len() function."

        return []

    if listLength == 0:

        return [] 

    if listLength == 1:

        try:

            return(QQ(rationalList[0]).numerator())

        except Exception:

            print "denominators:", rationalList[0], \

                    "has no \"numerator()\" member." 

            return [] 

    numeratorsList = []    

    for i in xrange(listLength):

        try:

            numeratorsList.append(QQ(rationalList[i]).numerator())

        except Exception:

            print "numerators:", rationalList[i], \

                    "has no \"numerator()\" member." 

            return [] 

    return numeratorsList

# End sro_numerators

print "\t...sageRationalOperations loaded"