How to resolve the algorithm Sudan function step by step in the Julia programming language
How to resolve the algorithm Sudan function step by step in the Julia programming language
Table of Contents
Problem Statement
The Sudan function is a classic example of a recursive function, notable especially because it is not a primitive recursive function. This is also true of the better-known Ackermann function. The Sudan function was the first function having this property to be published. The Sudan function is usually defined as follows (svg):
F
0
( x , y )
= x + y
F
n + 1
( x , 0 )
= x
if
n ≥ 0
F
n + 1
( x , y + 1 )
=
F
n
(
F
n + 1
( x , y ) ,
F
n + 1
( x , y ) + y + 1 )
if
n ≥ 0
{\displaystyle {\begin{array}{lll}F_{0}(x,y)&=x+y\F_{n+1}(x,0)&=x&{\text{if }}n\geq 0\F_{n+1}(x,y+1)&=F_{n}(F_{n+1}(x,y),F_{n+1}(x,y)+y+1)&{\text{if }}n\geq 0\\end{array}}}
Write a function which returns the value of F(x, y).
Let's start with the solution:
Step by Step solution about How to resolve the algorithm Sudan function step by step in the Julia programming language
The provided Julia code implements the Sudano function, which calculates a value based on three input integers (n
, x
, and y
) using a recursive definition. It also uses the Memoize
package to optimize the function's performance by caching previously calculated results. Here's a detailed explanation of the code:
-
Loading the
Memoize
Package:using Memoize
This line imports the
Memoize
package, which provides a macro (@memoize
) to memoize functions, improving their performance by storing and reusing previously calculated results. -
Defining the
sudan
Function:@memoize function sudan(n, x, y) return n == 0 ? x + y : y == 0 ? x : sudan(n - 1, sudan(n, x, y - 1), sudan(n, x, y - 1) + y) end
This function takes three integer arguments (
n
,x
, andy
) and computes a value based on the following logic:- If
n
is equal to 0, it returns the sum ofx
andy
. - If
y
is equal to 0, it returnsx
. - Otherwise, it calculates
sudan(n - 1, sudan(n, x, y - 1), sudan(n, x, y - 1) + y)
.
The
@memoize
macro wraps thesudan
function to memoize its results. When thesudan
function is called with the same arguments multiple times, it will return the cached result instead of recalculating it, which can significantly improve performance, especially for recursive functions with many repeated calculations. - If
-
Using the
foreach
Macro:foreach(t -> println("sudan($(t[1]), $(t[2]), $(t[3])) = ", sudan(t[1], t[2], t[3])), ((0,0,0), (1,1,1), (2,1,1), (3,1,1), (2,2,1)))
The code uses the
foreach
macro to iterate over a sequence of tuples and perform a specific action for each tuple.-
The sequence of tuples is defined as
((0,0,0), (1,1,1), (2,1,1), (3,1,1), (2,2,1))
. -
For each tuple
t
, the code prints a string of the formsudan(t[1], t[2], t[3]) =
followed by the result of callingsudan(t[1], t[2], t[3])
. So, it prints the value of thesudan
function for the given input tuples.
-
By using the Memoize
package to memoize the sudan
function, the code can calculate and print the results efficiently, even for larger input values of n
, as the function will not have to recompute previously calculated values.
Source code in the julia programming language
using Memoize
@memoize function sudan(n, x, y)
return n == 0 ? x + y : y == 0 ? x : sudan(n - 1, sudan(n, x, y - 1), sudan(n, x, y - 1) + y)
end
foreach(t -> println("sudan($(t[1]), $(t[2]), $(t[3])) = ",
sudan(t[1], t[2], t[3])), ((0,0,0), (1,1,1), (2,1,1), (3,1,1), (2,2,1)))
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