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→Grille cypher
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</source> | </source> | ||
{{Works in|[[Dyalog APL]], [[NARS2000]], [[dzaima/APL]]}} | {{Works in|[[Dyalog APL]], [[NARS2000]], [[dzaima/APL]]}} | ||
=== Frequency of characters in a string === | |||
The [[Outer Product]] allows for an intuitive way to compute the occurrence of characters at a given location in a string: | |||
<source lang=apl> | |||
'abcd' ∘.= 'cabbage' | |||
0 1 0 0 1 0 0 | |||
0 0 1 1 0 0 0 | |||
1 0 0 0 0 0 0 | |||
0 0 0 0 0 0 0 | |||
</source> | |||
Then it is simply a matter of performing a sum-reduce <source lang=apl inline>+/</source> to calculate the total frequency of each character:<ref name="Marshall LambaConf 2019">[[Marshall Lochbaum]] used this example as part of his talk on [[Outer Product]] at LambdaConf 2019.</ref> | |||
<source lang=apl> | |||
+/ 'abcd' ∘.= 'cabbage' | |||
2 2 1 0 | |||
</source> | |||
=== Parenthesis nesting level === | === Parenthesis nesting level === | ||
First we compare all characters to the opening and closing characters; | We can expand on the use of <source lang=apl inline>∘.</source> in the above example to perform more complex calculations. First we compare all characters to the opening and closing characters; | ||
<source lang=apl> | <source lang=apl> | ||
'()'∘.='plus(square(a),plus(square(b),times(2,plus(a,b)))' | '()'∘.='plus(square(a),plus(square(b),times(2,plus(a,b)))' | ||
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=== Grille cypher === | === Grille cypher === | ||
A [[wikipedia:grille (cryptography)|grille]] is a 500 year old method for encrypting messages. | A [[wikipedia:grille (cryptography)|grille]] is a 500 year old method for encrypting messages. | ||
[[File:Grille.png|none|500px|frameless | [[File:Grille.png|none|500px|frameless|The application of a grille cypher]] | ||
<p> | <p> | ||
Represent both the grid of letters and the grille as character matrices. | Represent both the grid of letters and the grille as character matrices. | ||
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ILIKEAPL | ILIKEAPL | ||
</source> | </source> | ||
===References=== | |||
<references/> | |||
{{APL development}} | {{APL development}} | ||