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Delphi - loop through a string

I'm trying to find out if String is a "mnemonic type" ... My mnemonic type consists of letters from "a" to "z" and from "A" to "Z", numbers from "0" to "9" and more " _ ". I am building the code as shown below. This should result in True if the given string matches my mnemonics, otherwise False:

 TRes := True;
 for I := 0 to (AString.Length - 1) do
 begin
     if not ((('0' <= AString[I]) and (AString[I] <= '9')) 
       or (('a' <= AString[I]) and (AString[I] <= 'z')) 
       or (('A' <= AString[I]) and (AString[I] <= 'Z')) 
       or (AString[I] = '_')) then
         TRes := False;
 end;

This code is always False.

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2 answers

I assume that since you checked the XE5 question and used indexing with a null index, your rows are based on a null value. But perhaps these assumptions were erroneous.

, . , . , if , .

, . - :

for C in AString do
begin
  if not (
        (('0' <= C) and (C <= '9'))  // C is in range 0..9
     or (('a' <= C) and (C <= 'z'))  // C is in range a..z
     or (('A' <= C) and (C <= 'Z'))  // C is in range A..Z
     or (C = '_')                    // C is _
  ) then
    TRes := False;
end;

, , , , .

, IsValidIdentifierChar:

function IsValidIdentifierChar(C: Char): Boolean;
begin
  Result :=  ((C >= '0') and (C <= '9'))
          or ((C >= 'A') and (C <= 'Z'))
          or ((C >= 'a') and (C <= 'z'))
          or (C = '_');
end;

@TLama, IsValidIdentifierChar , CharInSet:

function IsValidIdentifierChar(C: Char): Boolean;
begin
  Result := CharInSet(C, ['0'..'9', 'a'..'z', 'A'..'Z', '_']);
end;

:

TRes := True;
for C in AString do
  if not IsValidIdentifierChar(C) do 
  begin
    TRes := False;
    break;
  end;
+9

- 1. 0. ..., Delphi.

( ) - CharInSet.

function IsMnemonic( AString: string ): Boolean;
var
  Ch: Char;
begin
  for Ch in AString do 
    if not CharInSet( Ch, [ '_', '0'..'9', 'A'..'Z', 'a'..'z' ] ) then 
      Exit( False );
  Result := True;
end;
+5

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