Standard functions applying to AnsiString-type arguments

The list of the most important functions is following:

+ – concatenation. Operator S1=S2+S3; says that string from S3 must be appended to those from S2 and the result saved in S1.

==,!=, <, <=, >, >= – logical operations. Expression S1==S2 returns bool-type value; as well as expressions with other 5 operations.

Now let S be an AnsiString-type variable. Any following C++-Builder function F applying to S must be called in the form:

S.F(<additional parameters (if any) of F>);

(You will understand the motives of choosing such a form after you learn the notion of class of C++-Builder.)

S.c_str() – the result of this function is a zero-ended array contains a copy of string S. So if you have

AnsiString S = ”Honey”;

then it will be true that

S.c_str()[0] == ’H’

S.Length() – returns an int number – the current length of S.

S.IsEmpty() – returns a bool value (true if S is empty, false otherwise.)

S.Pos(sub_S) – returns the index of a first occurrence of a substring sub_S in the string S. If there are no occurrences of sub_S, it returns 0. Parameter can be a character, a constant string, or an AnsiString variable. So if S contains the string ”twins”, the value of S.Pos(”win”) equals to 2.

S.SubString(iBeg, sLen) – returns the substring of S, which begins at index iBeg and has sLen characters in length. So if S contains the string ”twins”, the value of S.SubString(2,3) equals to ”win”.

S.Delete(iBeg, sLen) – deletes sLen characters from starting from index iBeg and returns the result of deletion. So if S contains the string ”twins”, the value of S.Delete(2,3) equals to ”ts”.

S.Insert(S1, iIns) – inserts the string S1 into the string S in the position marked by index iIns. So if S contains the string ”twins”, and S1 contains ”o_tw”, the value of S.Insert(S1,3) equals to ”two_twins”. Just the same result will be obtained, if S1 contains ”two_” and we use function calls S.Insert(S1, 1) or S1.Insert(S, S1.Length()+1).

If you look the “Help” to the AnsiString-type you can see many other useful functions which help to manipulate this kind of data.

Let us now compose some programs dealing with AnsiStrings.

Example 1. Write a function that erases all ending blanks from a given AnsiString. One of possible solutions is:

AnsiString DelEndBlanks(AnsiString S)

{

const char Blank=' ';

int Len=S.Length();

if(Len==0)return S;

while((Len>0)&&

(S[Len]==Blank))

{S.Delete(Len,1);

Len--;

}

return S;

}

You see from this example that it is possible to call the AnsiString-function Delete in a mode normally used for functions having void returned values. But in fact Delete returns AnsiString value (more precisely, a pointer to an AnsiString value); and the above operator S.Delete(Len,1) is equivalent to S=S.Delete(Len,1). You will understand the cause of this equivalence after you will learn the notion of class of C++-Builder.

Example 2. Write a function that erases all multiple blanks from a given AnsiString (it means that any sequence of blanks must be substituted for a single blank). One of possible solutions is:

AnsiString DelMltplBlanks(AnsiString S)

{

const AnsiString twoBlanks=" ";

int Len=S.Length();

if(Len==0)return S;

int j=S.Pos(twoBlanks);

while((Len>0)&&

(j>0))

{S.Delete(j,1);

Len--;

j=S.Pos(twoBlanks);

}

return S;

}

Example 3. Write a function that returns the first word in a given AnsiString. It is assumed that blank symbol is the only possible delimiter of words in the string. One of possible solutions is:

AnsiString Get1stWordIn(AnsiString S)

{

const char Blank=' ';

int Len=S.Length();

if(Len==0)return S;

S=DelMltplBlanks(S);

S=DelEndBlanks(S);

S=DelBegBlanks(S); // write this function yourself

Len=S.Length();

if(Len==0)return S;

int j=S.Pos(Blank);

if(j==0)return S;

return S.SubString(1,j-1);

}

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