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00:00 - 23:0023:00 - 00:00

Adám
Adám
23:00
Oh, I guess that kind of works, but there's a much simpler answer: ⋄ 1÷1 2 3 4
TryAPL
TryAPL
@Adám 1 0.5 0.3333333333 0.25
Adám
Adám
How would you use APL to compute 1+2+3+4+5+6+7+8+9+10? Can you make the chat bot do it?
(This is not a trick question, the answer is pretty obvious.)
Elise
Elise
⋄ 10+45
TryAPL
TryAPL
@Elise Did you forget to add backticks around your code (`⋄ code`)? You can edit your message and I will edit my reply.
Adám
Adám
@Elise Haha, you're cheating by knowing the answer. What I had in mind was just taking my long formula and feeding it to the bot. Btw, press UpArrow and edit your message by inserting backticks to make the bot react.
Elise
Elise
23:06
⋄ 10+45
TryAPL
TryAPL
@Elise 55
Adám
Adám
Anyway, my point was that it is tedious to insert + symbols in all the spaces between the numbers. Let's make APL do that for us!
⋄ +/1 2 3 4 5 6 7 8 9 10
TryAPL
TryAPL
@Adám 55
Adám
Adám
That slash with a plus on its left means "insert plus between all the numbers".
Have you heard about the "factorial"?
Elise
Elise
Nope I haven't
Adám
Adám
23:09
OK, no worries. The "factorial of n" is simply a fancy name for the product of all numbers from 1 until n, that is 1×2×3×…×n. Now use APL to compute the factorial of 10.
Elise
Elise
⋄ !10
TryAPL
TryAPL
@Elise 3628800
Adám
Adám
Hey, how did you figure that out?
Do you think you can do it using the same pattern as I used above for the sum of all the numbers?
Elise
Elise
It works the same in a graphic calculator
Adám
Adám
More or less, but I thought you'd never heard of the factorial.
Elise
Elise
23:13
I knew what it was after you explained it, I just hadn't heard that term before
Adám
Adám
OK, let me teach you one more function. Like - and ! it can be used with a single argument. It's symbol is ⍳ which is the Greek letter iota. Iota corresponds to our letter i, and you can take it as standing for "indices" or "integers". It takes a number and generates all the numbers from 1 to that number: ⋄ ⍳10
TryAPL
TryAPL
@Adám 1 2 3 4 5 6 7 8 9 10
Adám
Adám
Now can you use this to compute the sum of all numbers from 1 to 100?
Elise
Elise
⋄ !⍳100
TryAPL
TryAPL 
@Elise
1 2 6 24 120 720 5040 40320 362880 3628800 39916800 479001600 6227020800 8.71782912E10 1.307674368E12 2.092278989E13 3.556874281E14 6.402373706E15 1.216451004E17 2.432902008E18 5.109094217E19 1.124000728E21 2.585201674E22 6.204484017E23 1.551121004E25 4.032914611E26 1.088886945E28 3.048883446E29 8.841761994E30 2.652528598E32 8.222838654E33 2.631308369E35 8.683317619E36 2.95232799E38 1.033314797E40 3.719933268E41 1.376375309E43 5.230226175E44 2.039788208E46 8.159152832E47 3.345252661E49 1.405006118E51 6.041526306E52 2.658271575E54 1.196222209E56 5.50262216E57 2.586232415E59 1.24139155…
Adám
Adám
23:15
Whoa, that's the factorial of all the numbers from 1 to 100. Some of those are rather large.
Elise
Elise
⋄+/⍳100
TryAPL
TryAPL
@Elise 5050
Adám
Adám
Very good.
Elise
Elise
I will be going to sleep now, thank you very much for teaching me!
Adám
Adám
No problem at all. You'll find me around here on most days and at most times. If you enjoyed this, then feel free to come back for more. If not, then that's perfectly fine. Sleep well!
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