(path,f)
return [(p[0],f(p[1])) for p in path]
accepts a path, ie [(t,x_t)], and transforms it into [(t,f(x)].
accepts a path, ie [(t,x_t)], and transforms it into [(t,f(x)].
accepts a path ie [ ( t x_t ) ] and transforms it into [ ( t f ( x ) ] .
def transform_path(path,f):
    "accepts a path, ie [(t,x_t)], and transforms it into [(t,f(x)]."
    return [(p[0],f(p[1])) for p in path]
def transform_path ( path , f ) : return [ ( p [ 0 ] , f ( p [ 1 ] ) ) for p in path ]