Lesson 13: String Manipulation Functions

 

In this lesson, we will learn how to use some of the string manipulation function such as Len, Right, Left, Mid, Trim, Ltrim, Rtrim, Ucase, Lcase, Instr, Val, Str  ,Chr and Asc.

 

(i)The  Len Function

 

The length function returns an integer value which is the length of a phrase or a sentence, including the empty spaces. The format is

Len (“Phrase”)

For example,

Len (VisualBasic) = 11 and Len (welcome to VB tutorial) = 22

The Len function can also return the number of digits or memory locations of a number that is stored in the computer. For example,

Private sub Form_Activate ( )

X=sqr (16)

Y=1234

Z#=10#

Print Len(x), Len(y), and Len (z)

End Sub

will produce the output  1, 4 , 8. The reason why the last value is 8 is because z# is a double precision number and so it is allocated more memory spaces.

(ii) The Right  Function

The Right function extracts the right portion of a phrase. The format is

Right (“Phrase”, n)

Where n is the starting position from the right of the phase where the portion of the phrase is going to be extracted.  For example,

 Right(“Visual Basic”, 4) = asic

(iii)The Left Function

The Left$ function extract the left portion of a phrase. The format is

Left(“Phrase”, n)

Where n is the starting position from the left of the phase where the portion of the phrase is going to be extracted.  For example,

 Left (“Visual Basic”, 4) = Visu

 (iv) The Ltrim Function

The Ltrim function trims the empty spaces of the left portion of the phrase. The format is

Ltrim(“Phrase”)

.For example,

 Ltrim (“  Visual Basic”, 4)= Visual basic

(v) The Rtrim Function

The Rtrim function trims the empty spaces of the right portion of the phrase. The format is

Rtrim(“Phrase”)

.For example,

Rtrim (“Visual Basic      ”, 4) = Visual basic

(vi)    The Trim function

 

The Ttrim function trims the empty spaces on both side of the phrase. The format is

Trim(“Phrase”)

.For example,

Trim (“   Visual Basic      ”) = Visual basic

(viii) The Mid Function

 

The Mid function extracts a substring from the original phrase or string. It takes the following format:

Mid(phrase, position, n)

Where position is the starting position of the phrase from which the extraction process will start and n is the number of characters to be extracted. For example,

Mid(“Visual Basic”, 3, 6) = ual Bas

(ix) The InStr function

 

 The InStr function looks for a phrase that is embedded within the original phrase and returns the starting position of the embedded phrase. The format is

Instr (n, original phase, embedded phrase)

Where n is the position where the Instr function will begin to look for the embedded phrase. For example

Instr(1, “Visual Basic”,” Basic”)=8

(x) The Ucase and the Lcase functions

 

The Ucase function converts all the characters of a string to capital letters. On the other hand, the Lcase function converts all the characters of a string to small letters. For example,

Ucase(“Visual Basic”) =VISUAL BASiC

Lcase(“Visual Basic”) =visual basic

(xi) The Str and Val functions

 

The Str is the function that converts a number to a string while the Val function converts a string to a number. The two functions are important when we need to perform mathematical operations.

(xii) The Chr and the Asc functions

 

The Chr function returns the string that corresponds to an ASCII code while the Asc function converts an ASCII character or symbol to the corresponding ASCII code. ASCII stands for “American Standard Code for Information Interchange”. Altogether there are 255 ASCII codes and as many ASCII characters. Some of the characters may not be displayed as they may represent some actions such as the pressing of a key or produce a beep sound. The format of the Chr function is

Chr(charcode)

and the format of the Asc function is

Asc(Character)

The following are some examples:

Chr(65)=A, Chr(122)=z, Chr(37)=% , Asc(“B”)=66, Asc(“&”)=38

 

 

 

 

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