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Who is right, me or my professor?

Who is right, me or my professor?

In a test i got this question:

Define a stream of all numbers in pascal triangle.

My answer was:

(define (pascal a b)
(cons-stream a (pascal(+a b)(b))

Knowing that it will give me a stream of all Natural numbers.
(and pascal triangle is basically all natural numbers..)
I didn't got one point on that question. Who do you think is right, me or my professor?


RE: Who is right, me or my professor?

Please can anyone help?

RE: Who is right, me or my professor?

Anyone with a clue in scheme, please, i need your help

RE: Who is right, me or my professor?

Hi namooth,
I don't understand why should your function have 2 arguments, i.e. (pascal a b) ?
IMHO it should depend only of one argument n, i.e. (pascal n).

For example for n=0..4.. the Pascal-triangle is:


0.row:                 1
1.row:              1     1
2.row:           1     2     1
3.row:        1     3     3     1
4.row:     1     4     6     4     1

IMHO, your professor probably wants to have a function which delivers for given n either
1. the numbers contained in triangle of order n, i.e:


for n=0: (1)
for n=1: (1)
for n=2: (1 2)
for n=3: (1 2 3)
for n=4: (1 2 3 4 6)
2. only the n-th row of Pascal triangle, i.e:


for n=0: (1)
for n=1: (1 1)
for n=2: (1 2 1)
for n=3: (1 3 3 1)
for n=4: (1 4 6 4 1)
I think, that the 2.function has better purpose, because then the combinatorial number C(n,k) could be taken as k-th element of sequence delivered by the function, for example:


C(4,0)=1 is the 0-th element of (1 4 6 4 1)
C(4,1)=4 is the 1-th element of (1 4 6 4 1)
C(4,2)=6 is the 2-nd element of (1 4 6 4 1)

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