import bisect

class InterpTable(object):
    '''
    a look up table that linearly interperlates between values
    '''
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __getitem__(self, v):
        j = bisect.bisect_left(self.x, v)
        i = j-1
        if i < 0 :
            return self.y[0]
        if j >= len(self.x) :
            return self.y[ -1 ]
        return self.y[i] + (v-self.x[i])*(self.y[j]-self.y[i])/(self.x[j]-self.x[i])