Should interp1.m function allow jumps in X-values?

[vivek dogra]

Hello, 
Currently, interp1.m allows at most one identical pair of values in X.  My concern is should it really do that? My arguments are as follows:

In my opinion repeated values should not be allowed for interpolation. Let's say i have following data 
points:

 x  f(x)
0    4
1    6

2    8

3    10

Now
 if i want to get f(1.5) then i will take the value midway between f(1) 
and f(2) which would be 7. Now in case i have repeated values the data 
points will be:

x   f(x)
0    4
1    6
1    7  
2    8 
3   10

Now
 in this case what f(1.5) will be? 7 or 7.5? (What will you call the 
best interpolation?) There will be ambiguity in this case. Also in the 
present case the sample points are nicely behaving so there is not much 
difference between 7 and 7.5. Although in some cases (if let's say f(1) =
 6 and f(1) = 9) there can be lot of difference between answers when we 
choose one data point over another. 
So Octave should not allow repeated x values.