How to split a string of only ten characters e.g.“12345*45688” into an array

Question

I\'m making a simple calculator where you type values into an edit box. I need to split the string into a number of arrays depending on how many *+-/ there are in the sum fo

Answer 1

If you wish to get the result of that equation, you should try a non-visual component, called CalcExpress. It's free and you can get it from here: CalcExpress

Download link is at the end of the page text

Answer 2

If you want to read something like that, especially if you want to evaluate mathematical expressions, you need more than just an array-splitter; you need a real parser. Doing it right requires a bit of compiler theory. I'd recommend you take a look at Let's Build A Compiler, a tutorial that covers everything you'll need to know about expression parsing (and a bit more, since he's actually building a simple compiler) and makes it easy to understand. All examples are in Turbo Pascal, so it should be easy for a Delphi coder to read.

Answer 3

Delphi XE has a SplitString function that does exactly what you need.

Answer 4

Here's a function which may help you on the way.

It breaks down an input string into an array of sub-strings, based upon a provided set of pre-defined character sets.

It will give you an array of strings, which will be ["22", "+", "22", "*", "22", "-", "22", "/", "22"].

From there on you'll have to identify the numbers and the operators, and you'll have to group and execute the calculations according to the rules for operator precedence.

TCharSet = Set of Char;
TStringArray = Array of String;

function GetSubStrings(InputString: String; CharacterSets: Array of TCharSet): TStringArray;
// Get Sub-strings
var
  Index: Integer;
  Character: Char;
  SubString: String;
  SubStringArray: TStringArray;
  CharacterSetIndex: Integer;
  PreviousCharacterSetIndex: Integer;
begin
  // Get
  SubString := '';
  SetLength(SubStringArray, 0);
  PreviousCharacterSetIndex := -1;
  for Index := 1 to Length(InputString) do
  begin
    // Character
    Character := InputString[Index];

    // Character Set Index
    CharacterSetIndex := GetCharacterSet(Character, CharacterSets);

    // Add
    if (CharacterSetIndex = PreviousCharacterSetIndex) or (Index = 1) then
      // Add Character to SubString
      SubString := SubString + Character
    else
    begin
      // Add SubString To SubString Array
      SetLength(SubStringArray, Length(SubStringArray) + 1);
      SubStringArray[Length(SubStringArray) - 1] := SubString;

      // New SubString
      SubString := Character;
    end;

    // Previous Character Set Index
    PreviousCharacterSetIndex := CharacterSetIndex;

    // Add last SubString
    if Index = Length(InputString)  then
    begin
      // Add SubString To SubString Array
      SetLength(SubStringArray, Length(SubStringArray) + 1);
      SubStringArray[Length(SubStringArray) - 1] := SubString;
    end;
  end;

  // Result
  Result := SubStringArray;
end; 

function GetCharacterSet(Character: Char; CharacterSets: Array of TCharSet): Integer;
// Get Character Set
var
  Index: Integer;
  CharacterSet: TCharSet;
begin
  // Get
  Result := -1;
  for Index := 0 to Length(CharacterSets) - 1 do
  begin
    // Character Set
    CharacterSet := CharacterSets[Index];

    // Check
    if Character in CharacterSet then
    begin
      // Result
      Result := Index;

      // Break
      Break;
    end;
  end;
end;