Euler 8.

[Robert L.]

> Find the greatest product of five consecutive digits in the 1000-digit
> number.

Scheme:

(define d
(filter-map
(lambda (c) (and (char-numeric? c) (string->number (string c))))
(string->list
"73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450")))

(apply max (map * d (cdr d) (cddr d) (cdddr d) (cddddr d)))

===>
40824

In Forth?

[Doug Hoffman]

On 11/27/19 4:36 PM, Robert L. wrote:
>> Find the greatest product of five consecutive digits in the 1000-digit
>> number.

Oforth:

"73167176531330624919225119674426574742355349194934"
"96983520312774506326239578318016984801869478851843" +
"85861560789112949495459501737958331952853208805511" +
"12540698747158523863050715693290963295227443043557" +
"66896648950445244523161731856403098711121722383113" +
"62229893423380308135336276614282806444486645238749" +
"30358907296290491560440772390713810515859307960866" +
"70172427121883998797908792274921901699720888093776" +
"65727333001053367881220235421809751254540594752243" +
"52584907711670556013604839586446706324415722155397" +
"53697817977846174064955149290862569321978468622482" +
"83972241375657056057490261407972968652414535100474" +
"82166370484403199890008895243450658541227588666881" +
"16427171479924442928230863465674813919123162824586" +
"17866458359124566529476545682848912883142607690042" +
"24219022671055626321111109370544217506941658960408" +
"07198403850962455444362981230987879927244284909188" +
"84580156166097919133875499200524063689912560717606" +
"05886116467109405077541002256983155200055935729725" +
"71636269561882670428252483600823257530420752963450" + const: s

: digitAsnumber \ idx -- n
s byteAt >digit ;
: 5numbers \ idx1 -- n1 n2 n3 n4 n5
| i | dup 4 + for: i [ i digitAsnumber ] ;

: go ( maxprod )
| i |
1 1000 5 - for: i [ i 5numbers * * * * dup maxprod >
if -> maxprod else drop then ]
maxprod . ;

0 go 40824 ok


Forth:
include FMS2.f

s" 73167176531330624919225119674426574742355349194934" >string value s
s" 96983520312774506326239578318016984801869478851843" s :add
s" 85861560789112949495459501737958331952853208805511" s :add
s" 12540698747158523863050715693290963295227443043557" s :add
s" 66896648950445244523161731856403098711121722383113" s :add
s" 62229893423380308135336276614282806444486645238749" s :add
s" 30358907296290491560440772390713810515859307960866" s :add
s" 70172427121883998797908792274921901699720888093776" s :add
s" 65727333001053367881220235421809751254540594752243" s :add
s" 52584907711670556013604839586446706324415722155397" s :add
s" 53697817977846174064955149290862569321978468622482" s :add
s" 83972241375657056057490261407972968652414535100474" s :add
s" 82166370484403199890008895243450658541227588666881" s :add
s" 16427171479924442928230863465674813919123162824586" s :add
s" 17866458359124566529476545682848912883142607690042" s :add
s" 24219022671055626321111109370544217506941658960408" s :add
s" 07198403850962455444362981230987879927244284909188" s :add
s" 84580156166097919133875499200524063689912560717606" s :add
s" 05886116467109405077541002256983155200055935729725" s :add
s" 71636269561882670428252483600823257530420752963450" s :add

: digitAsnumber \ idx -- n
s :at '0' - ;
: 5numbers \ idx1 -- n1 n2 n3 n4 n5
dup 5 + swap do i digitAsnumber loop ;

: go { maxprod }
999 5 - 0 do i 5numbers * * * * dup maxprod >
if to maxprod else drop then loop
maxprod . ;

0 go 40824 ok

[Ron AARON]

Except that Euler #8 as for the product of 13 consecutive digits...

[Doug Hoffman]

Thanks Ron. I never read the original Euler text and relied on
what was in the clf post. Shame on me...

The 13 digit solution would be essentially the same (technique).

-Doug