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113 changes: 113 additions & 0 deletions chapter-1/exercises/1.10.js
Original file line number Diff line number Diff line change
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//Exercise 1.10. The following function computes a mathematical function called Ackermann’s function.

function A(x,y) {
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Same notes on convention like https://github.com/tabdulradi/sicp/pull/3/files
I know you copied this code. But this teaches you not to paste any code blindly.

if (y === 0)
return 0;
else if (x === 0)
return 2 * y;
else if (y === 1)
return 2;
else
return A(x - 1, A(x, y - 1));
}

/* What are the values of the following expressions?
A(1, 10)
A(2, 4)
A(3, 3)
*/

//Solution

/*
A(1, 10)
A(0, A(1, 9))
A(0, A(0, A(1, 8)))
A(0, A(0, A(0, A(1, 7))))
A(0, A(0, A(0, A(0, A(1, 6)))))
A(0, A(0, A(0, A(0, A(0, A(1, 5))))))
A(0, A(0, A(0, A(0, A(0, A(0, A(1, 4)))))))
A(0, A(0, A(0, A(0, A(0, A(0, A(0, A(1, 3))))))))
A(0, A(0, A(0, A(0, A(0, A(0, A(0, A(0, A(1, 2)))))))))
A(0, A(0, A(0, A(0, A(0, A(0, A(0, A(0, A(0, A(1, 1)))))))))
A(0, A(0, A(0, A(0, A(0, A(0, A(0, A(0, A(0, 2))))))))
A(0, A(0, A(0, A(0, A(0, A(0, A(0, A(0, 4)))))))
A(0, A(0, A(0, A(0, A(0, A(0, A(0, 8))))))
A(0, A(0, A(0, A(0, A(0, A(0, 16)))))
A(0, A(0, A(0, A(0, A(0, 32))))
A(0, A(0, A(0, A(0, 64)))
A(0, A(0, A(0, 128))
A(0, A(0, 256)
A(0, 512)
1024

---------------------------------------------------------------------

A(2, 4)
A(1, A(2, 3))
A(1, A(1, A(2, 2)))
A(1, A(1, A(1, A(2, 1))))
A(1, A(1, A(1, 2)))
A(1, A(1, A(0, A(1, 1))))
A(1, A(1, A(0, 2)))
A(1, A(1, 4))
A(1, A(0, A(1, 3)))
A(1, A(0, A(0, A(1, 2))))
A(1, A(0, A(0, A(0, A(1, 1)))))
A(1, A(0, A(0, A(0, 2)))))
A(1, A(0, A(0, 4))))
A(1, A(0, 8)))
A(1, 16))
A(0, A(1, 15)))
A(0, A(0, A(1, 14))))
A(0, A(0, A(0, A(1, 13)))))
A(0, A(0, A(0, A(0, A(1, 12))))))
A(0, A(0, A(0, A(0, A(0, A(1, 11)))))))
A(0, A(0, A(0, A(0, A(0, A(0, A(1, 10))))))))
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A(1, 10) was defined above ;)

From previous substitution: A(1, 10) = 1024
A(0, A(0, A(0, A(0, A(0, A(0, 1024))))))
A(0, A(0, A(0, A(0, A(0, 2048)))))
A(0, A(0, A(0, A(0, 4096))))
A(0, A(0, A(0, 8192)))
A(0, A(0, A(0, 8192)))
A(0, A(0, 16384))
A(0, 32768)
65536

---------------------------------------------------------------------

A(3, 3)
A(2, A(3, 2))
A(2, A(2, A(3, 1)))
A(2, A(2, 2))
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A(2, 2) was calculated before

From previous substitution: A(2, 2) = 4
A(2, 4)
From previous substitution: A(2, 4) = 65536
65536
*/

//Consider the following functions, where A is the function defined above:

function f(n) {
return A(0,n);
}
function g(n) {
return A(1,n);
}
function h(n) {
return A(2,n);
}
function k(n) {
return 5 * n * n;
}

//Give concise mathematical definitions for the functions computed by the functions f, g, and h for positive integer values of . For example, (k n) computes .

//Solution

/*
f(n) --> 2 * n
g(n) --> 2 ** n
h(n) --> 2 ** 2 ** 2 .. n times (Tetration)
k(n) --> 5 * (n ** 2)
*/