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faster to_lower and to_upper #733

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merged 8 commits into from
Oct 13, 2023
Merged

faster to_lower and to_upper #733

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a0a03b8
faster to_lower and to_upper
jalvesz Mar 24, 2023
71337ba
Merge branch 'fortran-lang:master' into master
jalvesz Aug 28, 2023
8b7b1e8
faster chat_to_lower/upper
jalvesz Sep 12, 2023
a2aad14
Merge branch 'fortran-lang:master' into master
jalvesz Sep 12, 2023
b8dd3b4
to_lower/upper clearer constants definition
jalvesz Sep 14, 2023
c616095
Merge branch 'master' of https://github.com/jalvesz/stdlib
jalvesz Sep 14, 2023
27e928a
implicit whitespace shift parameter identification
jalvesz Oct 11, 2023
3e0811a
Merge branch 'fortran-lang:master' into master
jalvesz Oct 12, 2023
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20 changes: 8 additions & 12 deletions src/stdlib_ascii.fypp
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Original file line number Diff line number Diff line change
Expand Up @@ -223,31 +223,27 @@ contains
pure function char_to_lower(c) result(t)
character(len=1), intent(in) :: c !! A character.
character(len=1) :: t
integer, parameter :: wp= 32, la=65, lz= 90
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What are the origin of these numbers?

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I would prefer something like

integer, parameter :: la=iachar('A'), lz=iachar('Z')

as 65 is the ADE (ASCII Decimal Equivalent) of capital "A", and 90 is the ADE for capital Z". The advantage of numbers is that they are case-insensitive; but in this case I think the letters are much clearer. Longer descriptive names for the variables would be nice as well IMHO.

DECIMAL
*-------*-------*-------*-------*-------*-------*-------*-------*
| 00 nul| 01 soh| 02 stx| 03 etx| 04 eot| 05 enq| 06 ack| 07 bel|
| 08 bs | 09 ht | 10 nl | 11 vt | 12 np | 13 cr | 14 so | 15 si |
| 16 dle| 17 dc1| 18 dc2| 19 dc3| 20 dc4| 21 nak| 22 syn| 23 etb|
| 24 can| 25 em | 26 sub| 27 esc| 28 fs | 29 gs | 30 rs | 31 us |
| 32 sp | 33  ! | 34  " | 35  # | 36  $ | 37  % | 38  & | 39  ' |
| 40  ( | 41  ) | 42  * | 43  + | 44  , | 45  - | 46  . | 47  / |
| 48  0 | 49  1 | 50  2 | 51  3 | 52  4 | 53  5 | 54  6 | 55  7 |
| 56  8 | 57  9 | 58  : | 59  ; | 60  < | 61  = | 62  > | 63  ? |
| 64  @ | 65  A | 66  B | 67  C | 68  D | 69  E | 70  F | 71  G |
| 72  H | 73  I | 74  J | 75  K | 76  L | 77  M | 78  N | 79  O |
| 80  P | 81  Q | 82  R | 83  S | 84  T | 85  U | 86  V | 87  W |
| 88  X | 89  Y | 90  Z | 91  [ | 92  \ | 93  ] | 94  ^ | 95  _ |
| 96  ` | 97  a | 98  b | 99  c |100  d |101  e |102  f |103  g |
|104  h |105  i |106  j |107  k |108  l |109  m |110  n |111  o |
|112  p |113  q |114  r |115  s |116  t |117  u |118  v |119  w |
|120  x |121  y |122  z |123  { |124  | |125  } |126  ~ |127 del|
*-------*-------*-------*-------*-------*-------*-------*-------*

integer :: k

k = index( uppercase, c )
k = ichar(c)
if (k>=la.and.k<=lz) k = k + wp
t = char(k)

if ( k > 0 ) then
t = lowercase(k:k)
else
t = c
endif
end function char_to_lower

!> Returns the corresponding uppercase letter, if `c` is a lowercase
!> ASCII character, otherwise `c` itself.
pure function char_to_upper(c) result(t)
character(len=1), intent(in) :: c !! A character.
character(len=1) :: t
integer, parameter :: wp= 32, BA=97, BZ= 122
integer :: k

k = index( lowercase, c )
k = ichar(c)
if (k>=BA.and.k<=BZ) k = k - wp
t = char(k)

if ( k > 0 ) then
t = uppercase(k:k)
else
t = c
endif
end function char_to_upper

!> Convert character variable to lower case
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