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Tupling




A program transformation where several results are returned from a single traversal of a data structure.

E.g.

mean l = sum l / length l

==>

mean l = s/n where (s,n) = sumLen l

sumLen []



= (0,0) sumLen (x:xs) = (s+x, n+1) where (s,n) = sumLen xs

In procedural languages this technique is known as horizontal loop combination because it uses one loop to calculate several results.

Another form of tupling transformation is used to avoid repeated evaluation where a function generates several identical calls to itself.

By analysing the pattern of recursion (see descent function) it is possible to arrange for these identical calls to share results.

E.g.

fib 0 = 1 fib 1 = 1 fib n = fib (n-1) + fib (n-2)

==>

fib n = v where (_,v) = fibt n fibt 0 = (1,1) fibt n = (u+v,u) where (u,v) = fibt (n-1)



< Previous Terms Terms Containing tupling Next Terms >
tunnelling
TUPLE
tuple
tuple calculus
Tuple Space Smalltalk
horizontal loop combination
loop combination
program transformation
tupling
Turbo C
Turbo Debugger
turbo nerd
Turbo Pascal
Turbo Prolog


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