SYNOPSIS

b fold( b(a, b) f, [a] xs, b acc )

ARGUMENTS

f The function to use

xs The array

acc The initial value for folding.

DESCRIPTION

Applies a function across an array. For example, given a function sum which adds two integers:

 total = fold(sum,[1,2,3,4,5],0);
 putStrLn(String(total));

This prints the sum of the values in the array [1,2,3,4,5]
 The following example uses fold to calculate the final direction.

 data Direction = North | East | South | West;
 data Turn = Left | Right;
 Direction doTurn(Turn turn, Direction current) {
     case turn of {
         Left -> case current of {
             North -> new = West;
             | West -> new = South;
             | South -> new = East;
             | East -> new = North;
         }
         | Right -> case current of {
             North -> new = East;
             | West -> new = North;
             | South -> new = West;
             | East -> new = South;
         } 
     }
     return new;
 }
 
 Void main() {
     turns = [Left,Left,Left,Right,Right,Left,Right,Left,Left];
     original = West;
     final = fold(doTurn,turns,original);
     // final = North
 }

AUTHORS

Kaya standard library by Edwin Brady, Chris Morris and others ([email protected]). For further information see http://kayalang.org/

LICENSE

The Kaya standard library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License (version 2.1 or any later version) as published by the Free Software Foundation.

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