Difference between revisions of "String Functions and Manipulation in VB6"

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String Functions and Manipulation in VB6 including common functions such as Asc, Chr, Mid, Join, LSet, StrConv, StrReverse, Filter, Replace
 
String Functions and Manipulation in VB6 including common functions such as Asc, Chr, Mid, Join, LSet, StrConv, StrReverse, Filter, Replace
  
−
== Asc (function) ==
+
== Functions and Description ==
 +
 
 +
=== Asc (function) ===
 
Returns an Integer representing the character code corresponding to the first letter in a string.
 
Returns an Integer representing the character code corresponding to the first letter in a string.
  
Line 7: Line 9:
 
:Asc(string)
 
:Asc(string)
  
−
== Chr (function) ==
+
=== Chr (function) ===
 
Returns a String containing the character associated with the specified character code.
 
Returns a String containing the character associated with the specified character code.
  
Line 15: Line 17:
  
  
−
== InStr (function) ==
+
=== InStr (function) ===
 
Returns a Variant (Long) specifying the position of the first occurrence of one string within another.
 
Returns a Variant (Long) specifying the position of the first occurrence of one string within another.
  
Line 37: Line 39:
 
  MyPos = Instr(1, SearchString, "W")  ' Returns 0.
 
  MyPos = Instr(1, SearchString, "W")  ' Returns 0.
  
−
== InStrRev (function) ==
+
=== InStrRev (function) ===
 
New in VB6.
 
New in VB6.
  
Line 45: Line 47:
 
:InstrRev(stringcheck, stringmatch[, start[, compare]])
 
:InstrRev(stringcheck, stringmatch[, start[, compare]])
  
−
== Join (function) ==
+
=== Join (function) ===
 
New in VB6
 
New in VB6
  
 
Used to join arrays elements.
 
Used to join arrays elements.
  
−
== Mid (function) ==
+
=== Mid (function) ===
 
Returns a Variant (String) containing a specified number of characters from a string.
 
Returns a Variant (String) containing a specified number of characters from a string.
  
Line 56: Line 58:
 
:Mid(string, start[, length])
 
:Mid(string, start[, length])
  
−
== Replace (function) ==
+
=== Replace (function) ===
 
New in VB6.
 
New in VB6.
  
Line 77: Line 79:
 
  End Function
 
  End Function
  
−
== Reverse (function) ==
+
=== Reverse (function) ===
 
New in VB6.
 
New in VB6.
  
 
To reverse a string.
 
To reverse a string.
  
−
== Split (function) ==
+
=== Split (function) ===
 
New in VB6
 
New in VB6
  
Line 88: Line 90:
  
  
−
== StrComp (function) ==
+
=== StrComp (function) ===
 
Returns a Variant (Integer) indicating the result of a string comparison.
 
Returns a Variant (Integer) indicating the result of a string comparison.
  
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  string1 or string2 is Null          Null
 
  string1 or string2 is Null          Null
  
 +
== Performance Rating ==
 +
 +
table 1
 +
 +
{| class="stylish"
 +
|+ Relative performance of VB6 string functions
 +
|-
 +
! Function
 +
! Performance
 +
! Description
 +
|-
 +
| Len
 +
| class="num" | 1
 +
| Len(S) returns the number of ''characters'' in string S.<br />''(Note: works differently with UDTs)''
 +
|-
 +
| LenB
 +
| class="num" | 1
 +
| LenB(S) returns the number of ''bytes'' in S.
 +
|-
 +
| AscW
 +
| class="num" | 1
 +
| AscW(S) returns the ''Unicode value'' of the first character in S.
 +
|-
 +
| AscB
 +
| class="num" | 1
 +
| AscB(S) returns the ''first byte'' in S.
 +
|-
 +
| Asc
 +
| class="num" | 7
 +
| Asc(S) returns the ''ANSI value'' of the first character in S.
 +
|-
 +
| ChrW$
 +
| class="num" | 17
 +
| ChrW$(U) returns a string containing the ''Unicode character'' U.
 +
|-
 +
| ChrB$
 +
| class="num" | 18
 +
| ChrB$(B) returns a ''byte string'' containing the ''character'' B.
 +
|-
 +
| Chr$
 +
| class="num" | 24
 +
| Chr$(A) returns a string containing the ''ANSI character'' A.
 +
|-
 +
| Left$
 +
| class="num" | 18
 +
| Left$(S,x) returns x characters from the ''start'' of S.
 +
|-
 +
| Right$
 +
| class="num" | 21
 +
| Right$(S,x) returns x characters from the ''end'' of S.
 +
|-
 +
| Mid$
 +
| class="num" | 24
 +
| Mid$(S,x,y) returns y characters from S, starting at the ''x'th'' character.
 +
|-
 +
| CStr
 +
| class="num" | 36
 +
| CStr(x) returns the string representation of x (localized).
 +
|-
 +
| Str$
 +
| class="num" | 111
 +
| Str$(x) returns the string representation of x (not localized).
 +
|}
 +
 +
How to read the table: Calling Len takes 1 unit of time, while Asc takes 7 units. You can call Len 7 times in the same time you call Asc once.
 +
 +
table 2
  
 +
<TABLE CLASS="stylish">
 +
<CAPTION>Relative performance of VB6 string functions</CAPTION>
 +
<TR>
 +
<TH>Function</TH><TH>Performance</TH><TH>Description</TH>
 +
</TR>
 +
<TR>
 +
<TD>LTrim$</TD><TD CLASS="num">20</TD><TD>LTrim$(S) returns a copy of S without <EM>leading</EM> spaces.</TD>
 +
</TR>
 +
<TR>
 +
<TD>RTrim$</TD><TD CLASS="num">21</TD><TD>RTrim$(S) returns a copy of S without <EM>trailing</EM> spaces.</TD>
 +
</TR>
 +
<TR>
 +
<TD>Trim$</TD><TD CLASS="num">29</TD><TD>Trim$(S) returns a copy of S without <EM>leading or trailing</EM> spaces.</TD>
 +
</TR>
 +
<TR>
 +
<TD>Val</TD><TD CLASS="num">89</TD><TD>Val(S) returns the numeric value contained in S (non-localized).</TD>
 +
</TR>
 +
<TR>
 +
<TD>CInt</TD><TD CLASS="num">81</TD><TD>CInt(S) returns the integer value contained in S (localized, rounded).</TD>
 +
</TR>
 +
<TR>
 +
<TD>CDbl</TD><TD CLASS="num">103</TD><TD>CDbl(S) returns the double floating point value contained in S (localized).</TD>
 +
</TR>
 +
<TR>
 +
<TD>LCase$</TD><TD CLASS="num">53</TD><TD>LCase$(S) returns a copy of S with <EM>lower case letters</EM>.</TD>
 +
</TR>
 +
<TR>
 +
<TD>UCase$</TD><TD CLASS="num">53</TD><TD>UCase$(S) returns a copy of S with <EM>upper case letters</EM>.</TD>
 +
</TR>
 +
<TR>
 +
<TD>StrConv(vbLowerCase)</TD><TD CLASS="num">327</TD><TD>StrConv(S,vbLowerCase) returns a copy of S with <EM>lower case letters</EM>.</TD>
 +
</TR>
 +
<TR>
 +
<TD>StrConv(vbUpperCase)</TD><TD CLASS="num">333</TD><TD>StrConv(S,vbUpperCase) returns a copy of S with <EM>upper case letters</EM>.</TD>
 +
</TR>
 +
<TR>
 +
<TD>StrComp(vbBinaryCompare)</TD><TD CLASS="num">47</TD><TD>StrComp(S1,S2,vbBinaryCompare) compares string S1 and S2 based on their <EM>Unicode values</EM>.</TD>
 +
</TR>
 +
<TR>
 +
<TD>StrComp(vbTextCompare)</TD><TD CLASS="num">65</TD><TD>StrComp(S1,S2,vbTextCompare) compares string S1 and S2 in a <EM>locale-dependent, case-insensitive way</EM>.</TD>
 +
</TR>
 +
<TR>
 +
<TD>InStr(vbBinaryCompare)</TD><TD CLASS="num">14</TD><TD>InStr(x,S1,S2,vbBinaryCompare) looks for S2 in S1, starting at position x, in a <EM>locale-independent, case-sensitive way</EM>.</TD>
 +
</TR>
 +
<TR>
 +
<TD>InStr(vbTextCompare)</TD><TD CLASS="num">156</TD><TD>InStr(x,S1,S2,vbTextCompare) looks for S2 in S1, starting at position x, using <A HREF="instr.html#vbtextcompare">text comparison</A>.</TD>
 +
</TR>
 +
<TR>
 +
<TD><b style="color:black;background-color:#a0ffff">InStrRev</b>(vbBinaryCompare)</TD><TD CLASS="num">69</TD><TD><b style="color:black;background-color:#a0ffff">InStrRev</b>(S1,S2,x,vbBinaryCompare) looks for S2 in S1, from position x back to 1, in a <EM>locale-independent, case-sensitive way</EM>.</TD>
 +
</TR>
 +
<TR>
 +
<TD><b style="color:black;background-color:#a0ffff">InStrRev</b>(vbTextCompare)</TD><TD CLASS="num">193</TD><TD><b style="color:black;background-color:#a0ffff">InStrRev</b>(S1,S2,x,vbTextCompare) looks for S2 in S1, from position x back to 1, using <A HREF="instr.html#vbtextcompare">text comparison</A>.</TD>
 +
</TR>
 +
<TR>
 +
<TD><b style="color:black;background-color:#99ff99">Replace</b>(vbBinaryCompare)</TD><TD CLASS="num">375</TD><TD><b style="color:black;background-color:#99ff99">Replace</b>(S1,S2,S3,x,y,vbBinaryCompare) replaces S2 with S3 in S1, starting at position x, max y times, in a <EM>locale-independent, case-sensitive way</EM>.</TD>
 +
</TR>
 +
<TR>
 +
<TD><b style="color:black;background-color:#99ff99">Replace</b>(vbTextCompare)</TD><TD CLASS="num">513</TD><TD><b style="color:black;background-color:#99ff99">Replace</b>(S1,S2,S3,x,y,vbBinaryCompare) replaces S2 with S3 in S1, starting at position x, max y times, using <EM>text comparison</EM>.</TD>
 +
</TR>
 +
</TABLE>
  
 +
Reference: http://www.aivosto.com/vbtips/stringopt2.html
  
  

Revision as of 02:16, 12 February 2008

String Functions and Manipulation in VB6 including common functions such as Asc, Chr, Mid, Join, LSet, StrConv, StrReverse, Filter, Replace

Functions and Description

Asc (function)

Returns an Integer representing the character code corresponding to the first letter in a string.

Syntax

Asc(string)

Chr (function)

Returns a String containing the character associated with the specified character code.

Syntax

Chr(charcode)


InStr (function)

Returns a Variant (Long) specifying the position of the first occurrence of one string within another.

Syntax

InStr([start, ]string1, string2[, compare])

Example 

Dim SearchString, SearchChar, MyPos
SearchString ="XXpXXpXXPXXP"   ' String to search in.
SearchChar = "P"   ' Search for "P".

' A textual comparison starting at position 4. Returns 6.
MyPos = Instr(4, SearchString, SearchChar, 1)    

' A binary comparison starting at position 1. Returns 9.
MyPos = Instr(1, SearchString, SearchChar, 0)

' Comparison is binary by default (last argument is omitted).
MyPos = Instr(SearchString, SearchChar)   ' Returns 9.

MyPos = Instr(1, SearchString, "W")   ' Returns 0.

InStrRev (function)

New in VB6.

Similar to InStr but searches from end of string. Returns the position of an occurrence of one string within another, from the end of string.

Syntax

InstrRev(stringcheck, stringmatch[, start[, compare]])

Join (function)

New in VB6

Used to join arrays elements.

Mid (function)

Returns a Variant (String) containing a specified number of characters from a string.

Syntax

Mid(string, start[, length])

Replace (function)

New in VB6.

Returns a string in which a specified substring has been replaced with another substring a specified number of times.

Syntax

Replace(expression, find, replace[, start[, count[, compare]]])

Example 

Debug.print Replace("abababa", "a", "")

Example 

public Function StripOut(From as string, What as string) as string
  Dim i as Integer
  StripOut = From
  for i = 1 to len(What)
    StripOut = Replace(StripOut, mid$(What, i, 1), "")
  next i
End Function

Reverse (function)

New in VB6.

To reverse a string.

Split (function)

New in VB6

Split a string into a variant array.


StrComp (function)

Returns a Variant (Integer) indicating the result of a string comparison.

Syntax

StrComp(string1, string2[, compare])

Return Values 

If                                  StrComp returns
string1 is less than string2        -1
string1 is equal to string2 	     0
string1 is greater than string2     1
string1 or string2 is Null          Null

Performance Rating

table 1

Relative performance of VB6 string functions
Function Performance Description
Len 1 Len(S) returns the number of characters in string S.
(Note: works differently with UDTs)
LenB 1 LenB(S) returns the number of bytes in S.
AscW 1 AscW(S) returns the Unicode value of the first character in S.
AscB 1 AscB(S) returns the first byte in S.
Asc 7 Asc(S) returns the ANSI value of the first character in S.
ChrW$ 17 ChrW$(U) returns a string containing the Unicode character U.
ChrB$ 18 ChrB$(B) returns a byte string containing the character B.
Chr$ 24 Chr$(A) returns a string containing the ANSI character A.
Left$ 18 Left$(S,x) returns x characters from the start of S.
Right$ 21 Right$(S,x) returns x characters from the end of S.
Mid$ 24 Mid$(S,x,y) returns y characters from S, starting at the x'th character.
CStr 36 CStr(x) returns the string representation of x (localized).
Str$ 111 Str$(x) returns the string representation of x (not localized).

How to read the table: Calling Len takes 1 unit of time, while Asc takes 7 units. You can call Len 7 times in the same time you call Asc once.

table 2

Relative performance of VB6 string functions
FunctionPerformanceDescription
LTrim$20LTrim$(S) returns a copy of S without leading spaces.
RTrim$21RTrim$(S) returns a copy of S without trailing spaces.
Trim$29Trim$(S) returns a copy of S without leading or trailing spaces.
Val89Val(S) returns the numeric value contained in S (non-localized).
CInt81CInt(S) returns the integer value contained in S (localized, rounded).
CDbl103CDbl(S) returns the double floating point value contained in S (localized).
LCase$53LCase$(S) returns a copy of S with lower case letters.
UCase$53UCase$(S) returns a copy of S with upper case letters.
StrConv(vbLowerCase)327StrConv(S,vbLowerCase) returns a copy of S with lower case letters.
StrConv(vbUpperCase)333StrConv(S,vbUpperCase) returns a copy of S with upper case letters.
StrComp(vbBinaryCompare)47StrComp(S1,S2,vbBinaryCompare) compares string S1 and S2 based on their Unicode values.
StrComp(vbTextCompare)65StrComp(S1,S2,vbTextCompare) compares string S1 and S2 in a locale-dependent, case-insensitive way.
InStr(vbBinaryCompare)14InStr(x,S1,S2,vbBinaryCompare) looks for S2 in S1, starting at position x, in a locale-independent, case-sensitive way.
InStr(vbTextCompare)156InStr(x,S1,S2,vbTextCompare) looks for S2 in S1, starting at position x, using <A HREF="instr.html#vbtextcompare">text comparison</A>.
InStrRev(vbBinaryCompare)69InStrRev(S1,S2,x,vbBinaryCompare) looks for S2 in S1, from position x back to 1, in a locale-independent, case-sensitive way.
InStrRev(vbTextCompare)193InStrRev(S1,S2,x,vbTextCompare) looks for S2 in S1, from position x back to 1, using <A HREF="instr.html#vbtextcompare">text comparison</A>.
Replace(vbBinaryCompare)375Replace(S1,S2,S3,x,y,vbBinaryCompare) replaces S2 with S3 in S1, starting at position x, max y times, in a locale-independent, case-sensitive way.
Replace(vbTextCompare)513Replace(S1,S2,S3,x,y,vbBinaryCompare) replaces S2 with S3 in S1, starting at position x, max y times, using text comparison.

Reference: http://www.aivosto.com/vbtips/stringopt2.html


 

 

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