Analysis on the replacement of strings implemented by the mid Function

Analysis on the replacement of strings implemented by the mid Function

The mid function is generally used to return the neutron string of the original string, for example

Dim mystring, firstword, lastword, midwords

Mystring = "mid function Demo" creates a string.

Firstword = mid (mystring, 1, 3) 'returns "mid ".

Lastword = mid (mystring, 14, 4) 'returns "Demo ".

Midwords = mid (mystring, 5) 'returns "funcion

 

The specific functions are described as follows:

ReturnVariant(String), Which contains the specified number of characters in the string.

Syntax

Mid(String,Start[,Length])

MidThe function syntax has the following naming parameters:

Part	Description
String	Required parameter. String expression, which returns characters. IfStringContains null.Null.
Start	Required parameter. Long.StringThe character location of the extracted part. If StartExceedsStringNumber of characters,MidReturns a zero-length string ("").
Length	Optional;Variant(Long). Number of characters to return.If omitted orLengthExceeds the number of characters in the text (includingStartAnd returns the string fromStartAll characters to the end.

 

Description

Want to knowStringNumber of characters, availableLenFunction.

Note: MidbThe function acts on the byte data contained in a string, just as in the dual-byte character set (DBCS) language. Therefore, the parameter specifies the number of bytes rather than the number of characters. ForMidbSee the second example in the example topic.

Can we use it to replace some strings? Run the following function on your machine:

Option explicit

 

Public Function Test () as string

Dim s as string

S = "ABCD"

Mid (s, 1, 1) = "T"

Test = s

End Function

What did you find? Wow, the output string is changed to "tbcd! Yes, we can use mid to replace the string (very happy )! What if I change "T" to "TX? See the following code:

Option explicit

 

Public Function Test () as string

Dim s as string

S = "ABCD"

Mid (s, 1, 1) = "TX"

Test = s

End Function

Run it again. As expected, it is still "tbcd". Although mid can replace some simple strings, its precondition is that the string cannot exceed its return length (in this example, it is 1 ). Some netizens may ask what will happen if it is smaller than the return length? Well, Let's explain the experiment results. See:

Option explicit

 

Public Function Test () as string

Dim s as string

S = "ABCD"

Mid (s, 1, 3) = "TX"

Test = s

End Function

The result is as follows: "txcd ".

From the above results, mid can be replaced with some simple strings, but the following conditions must be observed:

The maximum length of replacement is determined by the maximum length returned by mid. If the length of the replacement string is greater than the return length, only the first part of the replacement string is used for replacement. If the length of the replacement string is smaller than the return length, the excess of the original string will be retained, and the rest will be replaced. Although mid has a very clever function in some occasions, if it involves common string operations, I suggest using it as much as possible.Replace (expression, find, replace [, start [, Count [, compare]).