#My APL page
My APL page at http://www.hakank.org/apl/ don't show correct APL characters on some browsers. Hopefully it works better at github. Note some hour later: Now that page seems to show the chars correct.
I tend to use Dyalog APL, and it's great dfns library (also used below).
##Some APL code Note: I'm not sure how well the special APL characters are shown in every browsers. There is an APL font (APL385.ttf) downloable from Dyalog which hopefully will give good result. Here is a direct link: Apl385.ttf
For the Project Euler problems, I have used some functions (e.g. fibonacci and factors) from the dfns library mentioned above; this may - or may not - be considering cheating.
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Euler1:
+/0=∧⌿3 5∘.|X/X←⍳999
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Euler2:
+/0=2|f/f←(4000000>f)/f←fibonacci¨⍳40
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Euler3:
⌈/factors 600851475143
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Euler4: Two versions on the same theme:
ispalin←{(⍴t)=+/(t)=(⌽t←⍕⍵)} ⌈/(∊ispalin¨P)/(P←∪∊,/A∘.×A← 99+⍳900)
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With ispalin "expanded" as an anonymous function:
⌈/(∊{(⍴t)=+/(t)=(⌽t←⍕⍵)}¨P)/P←∪∊A∘.×A←99+⍳900
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Euler 5:
∧/⍳20
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Euler 6:
((+/s)*2)-+/(s←⍳100)*2
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Euler 7:
pco 10001
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Euler 8: (Note: This don't work so well in the interactive GUI since the long line is stripped. Better to put it in a function.)
A←'7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450' ⌈/×/⍎¨A[((⍳(⍴A)-4)-1)∘.+⍳5]
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Euler 9: 1) I'm not very happy about this first version; it has too many transposes...
×/∊(1↑(↓c)/⍨1000=+/c←↑(b,¨{⍵*0.5}+/↑b×b←,a∘.,a←⍳500)) 2) This is better, and shorter: ×/∊(1↑c/⍨(1000=+/¨c←b,¨{⍵*0.5}+/¨b×b←,a∘.,a←⍳500))
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Euler 10:
The following is a principal solution of the problem but it yields LIMIT ERROR:
(~v∊v∘.×v)/v←1↓⍳2e6
Using the dfn sieve
+/sieve 2 to 2e6 Here is the recursive definition of [sieve](http://dfns.dyalog.com/n_sieve.htm) sieve←{ ⍝ Sieve of Eratosthenes.<br> ⍺←⍬ ⍝ Default no primes yet.<br> nxt←1↑⍵ ⍝ Next prime, and<br> msk←0≠nxt|⍵ ⍝ ... mask of non-multiples.<br> ^/1↓msk:⍺,⍵ ⍝ All non multiples - finished.<br> (⍺,nxt)∇ msk/⍵ ⍝ Sieve remainder.<br> }
##More about APL Here are some links about APL.
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Wikipedia: APL
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The J site has also some related APL papers/books
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Video: Dyalog APL for old timers
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[Other videos]((http://www.youtube.com/user/APLtrainer)
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Video: The Origins of APL - 1974
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Video: Kenneth Iverson's Memorial
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A blog by Catherine Lathwell doing a feature film about the origins of APL: Chasing Men Who Stare at Arrays
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Video: 50 years of APL