Fold: Difference between revisions
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{{primitive|f/y<br>x f/y}} |
{{primitive|f/y<br>x f/y}} |
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'''Fold''', also known as '''reduce''', '''foldl''' and '''over''', takes a dyadic function <code>f</code> and reduces an array <code>y</code> using it. |
'''Fold''', also known as '''reduce''', '''foldl''' and '''over''', takes a [[dyadic]] function <code>f</code> and reduces an array <code>y</code> using it. |
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Fold is a very strong utility. For example, you can sum a list using <code>+/</code>. |
Fold is a very strong utility. For example, you can sum a list using <code>+/</code>. |
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Revision as of 09:04, 31 July 2021
Fold
f/y
x f/y
x f/y
Fold, also known as reduce, foldl and over, takes a dyadic function f and reduces an array y using it.
Fold is a very strong utility. For example, you can sum a list using +/.
+/1 2 3 4
10
,/("ab";1;`d`a`b)
("a"
"b"
1
`d
`a
`b)
Specifying a left argument x uses it as an initial value.
3 +/1 2 3 4 13
When used with functions that take more than 2 arguments, fold can take multiple arguments, of which the first one is always the initial value.
{x,y,z}/["A";1 2 3;"BCD"]
("A";1;"B";2;"C";3;"D")