Unlock the Power of Tacit Programming in Dyalog 2024

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Discover the world of tacit programming in Dyalog through functional composition, benefits, and tools. Dive into compositional operators, trains, and exercises to enhance your programming skills. Explore the magic of function composition and the efficiency of tacit programming in this comprehensive guide.

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Glasgow 2024 Tacit Programming in Dyalog Stefan Kruger Ad m Brudzewsky Rich Park

Glasgow 2024 Tacit Programming in Dyalog Ad m Brudzewsky Rich Park Stefan Kruger

Glasgow 2024 Tacit Programming in Dyalog Ad m Brudzewsky xpqz.github.io/cultivations/Trains Rich Park youtu.be/Enlh5qwwDuY Train Spotting Stefan Kruger xpqz.github.io/learnapl/tacit

What is tacit programming? Explicit code mentions arguments: Expression ( /N)- /N 3 1 4 1 5 Tradfn R Range Y Dfn Tacit code implies arguments: Tacit {( / )-( / )} ( /- /) Tacit Programming in Dyalog 3

You already know some f/ f .g f\ A g f f B Operators derive tacit functions Tacit Programming in Dyalog 4

Function composition f g f g f fgh f g Function composition is plumbing that guides arguments to functions Tacit Programming in Dyalog 5

Benefits Arguments in operands Memorable (like and + ) Adjacency (like - and / ) Brevity (like F C) DRY (Don t Repeat Yourself; like ) Just a general feeling of superiority and awesomeness Tacit Programming in Dyalog 6

Overview Compositional operators (combinators) Trains (forks and atops) Tools Issues Plenty of exercises throughout Reading Tacit Programming in Dyalog 7

Over The shape of an outer product .f is ( ) , ( ) We can write this as , pre-process both Tacit Programming in Dyalog 8

Beside Location of th 1 in each element of is We can write this as pre-process right Tacit Programming in Dyalog 9

Atop Any-presence of in is / We can write this as / post-process result Tacit Programming in Dyalog 10

Commute A multiplication table of N is ( ) . ( ) We can write this as . selfie Tacit Programming in Dyalog 11

Tasks: Tacify! 1. 'Hello' {( ) ( )} 'World' 1 2. 'ab' 'cd' 'ab' {+/ } 'ab' 'de' 2 3. 8 100 0 { } 2.5 4 50 0 4. 10 4 1 0 { } 2.5 2 2 1 0 5. { \ = } 2 7 1 8 3 1 0 1 0 1 Tacit Programming in Dyalog 13

Train Introduction Also a type of composition Sequence of functions in isolation Most common mistake + 3 1 4 1 5 0.2 Parenthesised: (+ ) 3 1 4 1 5 Assigned (+ )3 1 4 1 5 2.8 Avg + Avg 3 1 4 1 5 Tacit Programming in Dyalog 14

Discussion: Writing Trains (fY)+(hY) (f+h)Y Tacit Programming in Dyalog 15

Discussion: Writing Trains (fY)+(hY) (f+h)Y (fY)+( Y) (f+ )Y Tacit Programming in Dyalog 16

Discussion: Writing Trains (fY)+(hY) (f+h)Y (fY)+( Y) (f+ )Y (XfY)+(XhY) X(f+h)Y Tacit Programming in Dyalog 17

Discussion: Writing Trains (fY)+(hY) (f+h)Y (fY)+( Y) (f+ )Y (XfY)+(XhY) X(f+h)Y (X )+(XhY) X( +h)Y Tacit Programming in Dyalog 18

Discussion: Writing Trains (fY)+(hY) (f+h)Y (fY)+( Y) (f+ )Y (XfY)+(XhY) X(f+h)Y (X )+(XhY) X( +h)Y Tacit Programming in Dyalog 19

Discussion: Writing Trains (fY)g(hY) (fgh)Y (fY)g( Y) (fg )Y g(hY) ( gh)Y (XfY)g(XhY) X(fgh)Y (X )g(XhY) X( gh)Y Tacit Programming in Dyalog 20

Discussion: Writing Trains (fY)g(hY) (fgh)Y (fY)g( Y) (fg )Y g(hY) ( gh)Y (XfY)g(XhY) X(fgh)Y (X )g(XhY) X( gh)Y g(XhY) X( gh)Y Tacit Programming in Dyalog 21

Discussion: Writing Trains (fY)g(hY) (fgh)Y (fY)g( Y) (fg )Y g(hY) ( gh)Y (XfY)g(XhY) X(fgh)Y (X )g(XhY) X( gh)Y g(XhY) X( gh)Y Tacit Programming in Dyalog 22

Discussion: Writing Trains (fY)g(hY) (fgh)Y (fY)g( Y) (fg )Y f(gY) ( fg)Y (XfY)g(XhY) X(fgh)Y (X )g(XhY) X( gh)Y f(XgY) X( fg)Y Tacit Programming in Dyalog 23

Train Details Some parts can be arrays: A g his{A} g h Two sub-types of trains: Fork: Atop: Longer trains: (d e f g h)is(d e (f g h)) (e f g h)is(e (f g h)) f g handA g h f g Tacit Programming in Dyalog 24

Example: Writing a Train { / ( \ ) = } 1 3 5 6 7 1 { / ( \ ) = ( )} 1 3 5 6 7 1 { / ( \ = ) } 1 3 5 6 7 1 {( / \ = ) } 1 3 5 6 7 1 ( / \ = ) 1 3 5 6 7 1 Tacit Programming in Dyalog 26

Tasks: Convert dfn to tacit 1. {1+ } 2 7 1 8 3 8 2 9 2. 3 1 4 {( )~( )} 1 6 1 3 4 6 3. { } 10 1 2 5 10 4. 2 {( ) } 2 7 1 8 3 7 Bonus: Find 3 ways to do this! 5. { *2} 2 7 1 8 3 4 49 1 64 9 Tacit Programming in Dyalog 27

BREAK Tacit Programming in Dyalog 28

Amazing tool: ]box on Tacit Programming in Dyalog 29

|+/ ]box on | + / Tacit Programming in Dyalog 30

|+/ ]box on t= -t=box | + / Tacit Programming in Dyalog 31

|+/ ]box on t= -t=box -t=tree | + / . | . . . / . . + . Tacit Programming in Dyalog 32

|+/ ]box on t= -t=box -t=tree -t=parens | + / . | . . . / . . + . |( ((+/) )) Tacit Programming in Dyalog 33

Tasks: Convert dfn to tacit 1. {( ) ( )} 1 1 1 0 1 1 0 0 2. ',;' {(~ ) } 'ab,de;fgh' 3 ab de fgh nums 2 7 1 8 3 3. 4 {( + ) } nums 4. {(+ ) } nums 5. Bonus task: Combine 3 & 4 into an ambivalent function. 4.5 4.75 4.2 Tacit Programming in Dyalog 34

Issues Arguments in operands Lots of monadic functions Dotting, Assignment, Recursion Selection Tacit Programming in Dyalog 35

Issues: Arguments in operands 10 {x @{x< } } 1 2 13 14 5 16 7 18 1 2 18 16 5 14 7 13 10 { @( < ) } 1 2 13 14 5 16 7 18 1 2 18 16 5 14 7 13 2 {( ) } 3 3 9 9 8 7 6 5 4 3 2 1 Tacit Programming in Dyalog 36

Issues: Lots of monadic functions { + } (+ ) ( ) (+ ( )) + ( ) (+ ) Tacit Programming in Dyalog 37

Issues: Recursion, Assignment, Dotting Namespace dotting Assignment Recursion {9 NC' ': n, n . NL-2 9} Tacit Programming in Dyalog 38

Issues: Selection {(3> ) } 3 1 4 1 5 4 5 (3 > ) 3 1 4 1 5 SYNTAX ERROR (3 > )3 1 4 1 5 SYNTAX ERROR (3 > )3 1 4 1 5 4 5 3 > 3 1 4 1 5 20.0 Conference Edition Tacit Programming in Dyalog 39

Issues: Selection 'aeiou' { [ ]} 'hello world' eoohll wrld 'aeiou' { } 'hello world' LENGTH ERROR 'aeiou'{ }'hello world' eoohll wrld 'aeiou' ( )'hello world' eoohll wrld 'aeiou' ( ) 'hello world' 21.0? Tacit Programming in Dyalog 40