Here's an exercise. Cover these three verbs.
po=: 13 :'|:y#:i.*/y'
cm=: 13 :'(*/y)(#"0)0,}:+/\y'
ac=: 13 :'((po + cm) ($y)#2){,'' '',.y'
TThese three verbs provide all combinations of a penny, nickel, dime and
quarter.
po 2 2 2
0 0 0 0 1 1 1 1
0 0 1 1 0 0 1 1
0 1 0 1 0 1 0 1
cm 2 2 2
0 0 0 0 0 0 0 0
2 2 2 2 2 2 2 2
4 4 4 4 4 4 4 4
ac 'PNDQ'
PPPPPPPP
NNNN NNNN
DD DD DD DD
Q Q Q Q Q Q Q Q
Use the tacit forms to see if you can write the See if you can write thre
explicit verbs. Then look at the definitions.
po
[: |: ] #: [: i. */
cm
*/ (#"0) 0 , [: }: +/\
ac
([: (po + cm) 2 #~ $) { [: , ' ' ,. ]
Tacitverbs are executed from right to left.
You can chop them into words to help make the
Verbs easier to find.
;:'([: (po + cm) 2 #~ $) { [: , '' '' ,. ]'
┌─┬──┬─┬──┬─┬──┬─┬─┬─┬─┬─┬─┬─┬──┬─┬───┬──┬─┐
│(│[:│(│po│+│cm│)│2│#│~│$│)│{│[:│,│' '│,.│]│
└─┴──┴─┴──┴─┴──┴─┴─┴─┴─┴─┴─┴─┴──┴─┴───┴──┴─┘
I find trees helpful too. Note when J inserts [: and when it doesn't
5!:4 <'ac'
┌─ [:
│ ┌─ po
├────┼─ +
┌───┤ └─ cm
│ │
│ │ ┌─ 2
│ └────┼─ ~ ─── #
──┤ └─ $
├─ {
│ ┌─ [:
│ ├─ ,
└───┤ ┌─ ' '
└────┼─ ,.
└─ ]
Another day start with the explicit and write the explicit.
Next take an explicit verb you have written that 13: has modified. And work
backwards from the tacit form.
Just a strategy I've used.
Linda
-----Original Message-----
From: Programming <[email protected]> On Behalf Of
'robert therriault' via Programming
Sent: Friday, July 26, 2019 7:48 PM
To: [email protected]
Subject: Re: [Jprogramming] Learning Tacit Programming
Hi Josh,
I have always leaned heavily on Henry Rich's excellent book "J for C
Programmers"
https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.jsoftware.com%2Fhelp%2Fjforc%2Fcontents.htm%23_Toc191734581&data=02%7C01%7C%7C4cad6234f9974c02b3ce08d71223a6f8%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636997816641507591&sdata=5Utd2UwjRm73sQOaLUTXCzH9%2BheXZ3oB4EOnx4feHyA%3D&reserved=0
In particular the section "Tacit Programs" helps with the technical details
https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.jsoftware.com%2Fhelp%2Fjforc%2Ftacit_programs.htm%23_Toc191734582&data=02%7C01%7C%7C4cad6234f9974c02b3ce08d71223a6f8%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636997816641517602&sdata=cuYJcfZm%2BZWt4FNBDWoVhBxBAwV62brSMTZTyDG%2Bz04%3D&reserved=0
Also, using 13 : to declare verbs usually gives a tacit version of explicit one
line verbs
13 : ' x + y * y'
[ + ] * ]
13 : ' x +: @ * y'
+:@*
Cheers, bob
> On Jul 26, 2019, at 4:20 PM, The3DSquare Josh Yang
> <[email protected]> wrote:
>
> I was wondering if you guys have any resources for learning tacit
> programming in J. I've been struggling with tacit programming,
> probably because all the other programming languages are mainly
> explicit. Something like "Tacit programming for the explicit
> programmer" would be great since I often fail to derive the tacit
> equivalent of a series of explicit eeaxpressions (especially when there are
> mutable variables).
>
> I know I need to think differently, but having some guidance would
> help greatly.
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