# XML "function" nodes that transform their contents

            cause)

    def __init__(self, cause):

        exc.ExceptionWithCause.__init__(self, 'Invalid input value', cause)

    return [(func(name), value) for name, value in params]

def variadic_args(node):

    args = map_names(float, xml_dom.NodeEntryIter(node))

    args.sort()

    return [value for name, value in args]

    return [(name, func(value)) for name, value in items]

def cast(type_, val):

    '''Throws FormatException if can't cast'''

    try: return type_(val)

    except ValueError, e: raise FormatException(e)

def conv_items(type_, items):

    return map_items(lambda val: cast(type_, val),

        xml_dom.TextEntryOnlyIter(items))

def pop_value(items, name='value'):

    '''@param name Name of value param, or None to accept any name'''

    try: last = items.pop() # last entry contains value

    except IndexError: return None # input is empty and no actions

    if name != None and last[0] != name: return None # input is empty

    return last[1]

    '''Merges siblings in root that are marked as mergeable.

    Used to recombine pieces of nodes that were split apart in the mappings.

    '''

    for name in set((c.tagName for c in xpath.get(root, '*[@merge=1]'))):

        xml_dom.merge_by_name(root, name)

    # Recurse

    for child in xml_dom.NodeElemIter(root): merge_tagged(child)

def is_var_name(str_): return str_.startswith(var_name_prefix)

def is_var(node):

    return xml_dom.is_text_node(node) and is_var_name(xml_dom.value(node))

    return name.startswith('_') and name != '_' # '_' is default root node name

def is_func(node): return is_func_name(node.tagName)

def is_xml_func_name(name): return is_func_name(name) and name in funcs

def is_xml_func(node): return is_xml_func_name(node.tagName)

    return scalar.is_scalar(value) and not (util.is_str(value)

        and is_var_name(value))

    if len(children) == 1: xml_dom.replace(node, children[0][1])

    for child in xml_dom.NodeElemIter(node): simplify(child)

    merge_tagged(node)

    else: # these should not run on functions because they would remove args

          functions are treated specially, depending on the db param (below).

    @param db

        * If None: Non-relational functions other than structural functions are

          replaced with their last parameter (usually the value), not evaluated.

          This is used in column-based mode to remove XML-only functions.

        * If != None: Relational functions are evaluated directly. This is used

          in row-based mode to combine relational and XML functions.

    row_mode = has_rel_funcs and db != None

    column_mode = has_rel_funcs and db == None

    if len(items) == 1 and items[0][0].isdigit(): # has single numeric param

        # pass-through optimization for aggregating functions with one arg

        value = items[0][1] # pass through first arg

            for n, v in items)): return # preserve complex funcs

        try: value = sql_io.put(db, name, dict(items), on_error=on_error)

            # possibly a built-in function of db_xml.put()

        if column_mode and is_rel_func(name): return # preserve relational funcs

        # otherwise XML-only in column mode, or DB-only in XML output mode

        value = pop_value(items, None) # just replace with last param

            exc.add_traceback(e)

                '\n'+term.emph_multiline(str_)))

# Function names must start with _ to avoid collisions with real tags

# Functions take params (node) and have no return value

    values = [v for k, v in xml_dom.NodeTextEntryIter(node)]

    if lists.and_(map(is_scalar, values)): # all constants

        xml_dom.replace_with_text(node, lists.and_(values))

    else: passthru(node)

simplifying_funcs['_and'] = _and

    values = [v for k, v in xml_dom.NodeTextEntryIter(node)]

    if lists.and_(map(is_scalar, values)): # all constants

        xml_dom.replace_with_text(node, lists.or_(values))

    else: passthru(node)

simplifying_funcs['_or'] = _or

    '''Returns whether its node is non-empty'''

    xml_dom.replace_with_text(node, not xml_dom.is_empty(node))

simplifying_funcs['_exists'] = _exists

    *Must* be run to remove conditions that functions._if() can't handle.

    Note: Can add `@name` attr to distinguish separate _if statements.

    '''

    then = params.get('then', None)

    cond = params.get('cond', None)

    else_ = params.get('else', None)

    if cond == None: xml_dom.replace(node, else_) # always False

    elif then == else_: xml_dom.replace(node, then) # always same value

    elif is_var(cond): pass # can't simplify variable conditions

    elif xml_dom.is_text_node(cond) and bool(xml_dom.value(cond)): # always True

        xml_dom.replace(node, then)

simplifying_funcs['_if'] = _if

    '''

    *Must* be run to remove conditions that functions._nullIf() can't handle.

    '''

    params = dict(xml_dom.NodeEntryIter(node))

    null = params.get('null', None)

    value = params.get('value', None)

    if value == None: xml_dom.prune_parent(node) # empty

    elif null == None: xml_dom.replace(node, value) # nothing to null out

simplifying_funcs['_nullIf'] = _nullIf

def _eq(node):

    params = dict(xml_dom.NodeTextEntryIter(node))

    left = params.get('left', None)

    right = params.get('right', None)

    if is_scalar(left) and is_scalar(right): # constant

        xml_dom.replace_with_text(node, left == right)

    elif left == right: xml_dom.replace_with_text(node, True) # always True

simplifying_funcs['_eq'] = _eq

simplifying_funcs['_alt'] = passthru

simplifying_funcs['_max'] = passthru

    xml_dom.prune_children(node)

    try: first = args[0]

    except IndexError: first = None

    xml_dom.replace(node, first)

simplifying_funcs['_first'] = _first

def _env(node):

    except KeyError, e: raise SyntaxError(e)

# Function names must start with _ to avoid collisions with real tags

    if value == None: return None # input is empty

        for repl, with_ in items:

            if re.match(r'^\w+$', repl):

                repl = r'(?<![^\W_])'+repl+r'(?![^\W_])' # match whole word

            value = re.sub(repl, with_, value)

    if value == None: return None # input is empty

        for action, units_ in items:

            units_ = util.none_if(units_, u'')

            if action == 'default': units.set_default_units(quantity, units_)

                try: quantity = units.convert(quantity, units_)

    def __init__(self):

        Exception.__init__(self, 'CV (coefficient of variation) values are only'

            ' allowed for ratio scale data '

            '(see <http://en.wikipedia.org/wiki/Coefficient_of_variation>)')

    except IndexError: return None # input is empty

    items = dict(conv_items(strings.ustr, items))

    try: value = items['value']

    except KeyError: return None # input is empty

    if not value.isupper(): return value # pass through other coordinate formats

    try: return util.cast(str, angles.compass2heading(value)) # ignore None

    except KeyError, e: raise FormatException(e)

funcs['_compass'] = _compass