# Happy Christmas Eve! 🎄 **URL:** \ **Category:** Uncategorized\ **Created:** [December 24, 2020, 5:02pm UTC](https://fortran-lang.discourse.group/t/happy-christmas-eve/519 "2020-12-24T17:02:36Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![ivanpribec](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/ivanpribec/32/3290_2.png) [@ivanpribec](https://fortran-lang.discourse.group/u/ivanpribec)\ **Post date:** [December 24, 2020, 5:02pm UTC](https://fortran-lang.discourse.group/t/happy-christmas-eve/519/1 "2020-12-24T17:02:36Z")
Merry Christmas Eve, all! Run the code below to produce some Christmas trees: ```auto do i=3,9 do k=1,i print*,repeat(' ',i-k)//repeat('*',2*k-1) enddo print*,repeat(' ',i-1)//'*' if (i<9) write(*,*) enddo end ``` (This is my [code golf](https://code.golf/christmas-trees#fortran) solution with 123 characters. Apparently, it is possible to do it with less than 70 characters!) ---
**Author:** ![urbanjost](https://avatars.discourse-cdn.com/v4/letter/u/0ea827/32.png) [@urbanjost](https://fortran-lang.discourse.group/u/urbanjost)\ **Post date:** [December 24, 2020, 10:49pm UTC](https://fortran-lang.discourse.group/t/happy-christmas-eve/519/2 "2020-12-24T22:49:35Z")
Reminds me of the old obfustication challenges: ```auto write(*,'(*(a/),a/)')([(repeat(' ',i-k)//repeat('*',2*k-1),k=1,i),repeat(' ',i-1)//'*'],i=3,9) end ``` ---
**Author:** ![ivanpribec](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/ivanpribec/32/3290_2.png) [@ivanpribec](https://fortran-lang.discourse.group/u/ivanpribec)\ **Post date:** [December 24, 2020, 10:54pm UTC](https://fortran-lang.discourse.group/t/happy-christmas-eve/519/3 "2020-12-24T22:54:44Z")
Your code works with `ifort`, but with `gfortran` I get: ```nohighlight Fortran runtime error: Argument NCOPIES of REPEAT intrinsic is negative (its value is -1) ``` ---
**Author:** ![urbanjost](https://avatars.discourse-cdn.com/v4/letter/u/0ea827/32.png) [@urbanjost](https://fortran-lang.discourse.group/u/urbanjost)\ **Post date:** [December 24, 2020, 11:16pm UTC](https://fortran-lang.discourse.group/t/happy-christmas-eve/519/4 "2020-12-24T23:16:27Z")
```auto write(*,'(*(a/),a/)')([(repeat(' ',i-k)//repeat('*',2*k-1),k=1,i),repeat(' ',i-1)//'*'],i=3,9) ``` Just having fun, but it shows how hard you can make something be to debug, doesn’t it? But … ```auto do i=3,9 do k=1,i write(*,*)i-k,2*k-1 enddo write(*,*)i-1 enddo end ``` should see what it does to nvfortran! The description I have on hand doesn’t say zero is disallowed, do not see a negative. Now I actually have to think about it:\> ---
**Author:** ![nshaffer](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/nshaffer/32/161_2.png) [@nshaffer](https://fortran-lang.discourse.group/u/nshaffer)\ **Post date:** [December 24, 2020, 11:23pm UTC](https://fortran-lang.discourse.group/t/happy-christmas-eve/519/5 "2020-12-24T23:23:31Z")
```auto use iso_fortran_env open(output_unit,encoding="UTF-8") write(*,*)char(127876,selected_char_kind("ISO_10646")) end ``` 114 characters 😁 ---
**Author:** ![jeremie.vandenplas](https://avatars.discourse-cdn.com/v4/letter/j/76d3ee/32.png) [@jeremie.vandenplas](https://fortran-lang.discourse.group/u/jeremie.vandenplas)\ **Post date:** [December 25, 2020, 12:46am UTC](https://fortran-lang.discourse.group/t/happy-christmas-eve/519/6 "2020-12-25T00:46:40Z")
Starting from your proposition, in 93 characters: ```auto print'(*(a/))',((repeat(' ',i-k+1)//repeat('*',2*k-1),k=1,i),repeat(' ',i)//'*','',i=3,9) end ``` ---
**Author:** ![urbanjost](https://avatars.discourse-cdn.com/v4/letter/u/0ea827/32.png) [@urbanjost](https://fortran-lang.discourse.group/u/urbanjost)\ **Post date:** [December 25, 2020, 1:39am UTC](https://fortran-lang.discourse.group/t/happy-christmas-eve/519/7 "2020-12-25T01:39:16Z")
All nice! No one run the obfuscation version with gfortran unless you are curious whether you will get a bus error or fill /var/crash first. Does not seem right to give or receive a bug report this time of year, so some other time – but a real doozie. Assuming your terminal emulator handles ANSI in-line control sequences, this one should be safe to run with gfortran ```auto !write(*,'(*(a,/),a,/)')([(repeat(' ',i-k)//repeat('*',2*k-1),k=1,i),repeat(' ',i-1)//'*'],i=3,9) !write(*,'(*(i0,/),i0/)')([(i-k,2*k-1,k=1,i),i-1],i=3,9) implicit none integer, allocatable :: seed(:) integer,parameter :: first=1,last=8 integer :: i,k,n,r real :: rand_val call random_seed(size = n) allocate(seed(n)) call random_seed(get=seed) write(*,'(a,a,*(a,/),a,/)')char(27)//'[H'//char(27)//'[J' do call random_number(rand_val) r=first+floor((last+1-first)*rand_val) write(*,'(a,*(a,/),a,/)')char(27)//'[H',([& &( repeat(' ',min(8,max(0,i-k)))//repeat(char(33+r+k),min(17,max(0,2*k-1))) ,k=1,i),& &repeat(' ',min(max(0,i-1),9) )//'*'],i=8,9) enddo end ``` Merry Christmas! ---
**Author:** ![vmagnin](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/vmagnin/32/28_2.png) [@vmagnin](https://fortran-lang.discourse.group/u/vmagnin)\ **Post date:** [December 25, 2020, 9:41am UTC](https://fortran-lang.discourse.group/t/happy-christmas-eve/519/8 "2020-12-25T09:41:52Z")
> [@nshaffer](#): > > ```auto > use iso_fortran_env > open(output_unit,encoding="UTF-8") > write(*,*)char(127876,selected_char_kind("ISO_10646")) > end > > ``` An “improved” version (53 characters): ```fortran open(unit=6,encoding="UTF-8") print*,char(127876,4) end ``` ```auto $ gfortran -std=f2018 -Wall -Wextra -pedantic essai2.f90 && ./a.out 🎄 ```