How to detect if a character from a string is upper or lower case? - string

Question

I'm expanding a class of mine for storing generic size strings to allow more flexible values for user input. For example, my prior version of this class was strict and allowed only the format of 2x3 or 9x12. But now I'm making it so it can support values such as 2 x 3 or 9 X 12 and automatically maintain the original user's formatting if the values get changed.
The real question I'm trying to figure out is just how to detect if one character from a string is either upper or lower case? Because I have to detect case sensitivity. If the deliminator is 'x' (lowercase) and the user inputs 'X' (uppercase) inside the value, and case sensitivity is turned off, I need to be able to find the opposite-case as well.
I mean, the Pos() function is case sensitive...

Answer 1

Delphi 7 has UpperCase() and LowerCase() functions for strings. There's also UpCase() for characters.
If I want to search for a substring within another string case insensitively, I do this:
if Pos('needle', LowerCase(hayStack)) > 0 then
You simply use lower case string literals (or constants) and apply the lowercase function on the string before the search. If you'll be doing a lot of searches, it makes sense to convert just once into a temp variable.
Here's your case:
a := '2 x 3'; // Lowercase x
b := '9 X 12'; // Upper case X
x := Pos('x', LowerCase(a)); // x = 3
x := Pos('x', LowerCase(b)); // x = 3
To see if a character is upper or lower, simply compare it against the UpCase version of it:
a := 'A';
b := 'b';
upper := a = UpCase(a); // True
upper := b = UpCase(b); // False

Answer 2

try using these functions (which are part of the Character unit)
Character.TCharacter.IsUpper
Character.TCharacter.IsLower
IsLower
IsUpper
UPDATE
For ansi versions of delphi you can use the GetStringTypeEx functions to fill a list with each ansi character type information. and thne compare the result of each element against the $0001(Upper Case) or $0002(Lower Case) values.
uses
Windows,
SysUtils;
Var
LAnsiChars: array [AnsiChar] of Word;
procedure FillCharList;
var
lpSrcStr: AnsiChar;
lpCharType: Word;
begin
for lpSrcStr := Low(AnsiChar) to High(AnsiChar) do
begin
lpCharType := 0;
GetStringTypeExA(LOCALE_USER_DEFAULT, CT_CTYPE1, #lpSrcStr, SizeOf(lpSrcStr), lpCharType);
LAnsiChars[lpSrcStr] := lpCharType;
end;
end;
function CharIsLower(const C: AnsiChar): Boolean;
const
C1_LOWER = $0002;
begin
Result := (LAnsiChars[C] and C1_LOWER) <> 0;
end;
function CharIsUpper(const C: AnsiChar): Boolean;
const
C1_UPPER = $0001;
begin
Result := (LAnsiChars[C] and C1_UPPER) <> 0;
end;
begin
try
FillCharList;
Writeln(CharIsUpper('a'));
Writeln(CharIsUpper('A'));
Writeln(CharIsLower('a'));
Writeln(CharIsLower('A'));
except
on E:Exception do
Writeln(E.Classname, ': ', E.Message);
end;
Readln;
end.

Answer 3

if myChar in ['A'..'Z'] then
begin
// uppercase
end
else
if myChar in ['a'..'z'] then
begin
// lowercase
end
else
begin
// not an alpha char
end;
..or D2009 on..
if charInSet(myChar,['A'..'Z']) then
begin
// uppercase
end
else
if charInSet(myChar,['a'..'z']) then
begin
// lowercase
end
else
begin
// not an alpha char
end;

Answer 4

The JCL has routines for this in the JclStrings unit, eg CharIsUpper and CharIsLower. SHould work in Delphi 7.

Answer 5

AnsiPos() is not case-sensitive. You can also force upper or lower case, irrespective of what the user enters using UpperCase() and LowerCase().
Just throwing this out there since you may find it far more simple than the other (very good) answers.