String and General ProceduresString and General Procedures

Answer to the last question of Answer to the last question of Exam 1Exam 1

Start

Get a number

Divide the Number

By 2

Is the quotient Equal to 1?

PrintThe Remainto the left of

previous remains

No

Print 1To the left of

Previous remainsEnd

YesOutput number

If numberEqual to 1 or

0

Yes

No

Statistics of Exam 1Statistics of Exam 1

Max: 98Max: 98 Average: 75.18Average: 75.18 Median: 75Median: 75

Midterm grade

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FrequencyCumulative %

StringsStrings

Strings are variables that hold letters, Strings are variables that hold letters, words, sentences, or even numberswords, sentences, or even numbers

String holds a bunch of ASCII codes.String holds a bunch of ASCII codes. You can not do mathematical operations on You can not do mathematical operations on

string.string. So you need to use Val(string) function to So you need to use Val(string) function to

convert strings to numbers.convert strings to numbers.

String VariablesString Variables

Declaring StringsDeclaring Strings

Dim Phrase1 As StringDim Phrase1 As String Assigning value to a string variableAssigning value to a string variable

– Phrase1 = “Hello”Phrase1 = “Hello”

Phrase1

H

e

l

l

o

72

101

108

108

111

ASCII code

& Adding Two Strings && Adding Two Strings &

Phrase1 = TextBox1.TextPhrase1 = TextBox1.Text

Phrase2 = TextBox2.TextPhrase2 = TextBox2.Text

Sentence = Phrase1 & Phrase2Sentence = Phrase1 & Phrase2

Adding two strings is called Adding two strings is called ““CONCATENATINGCONCATENATING””

Adding text to a String VariableAdding text to a String Variable

Dim TheAnswer as StringDim TheAnswer as String TheAnswer = “a plague upon society!”TheAnswer = “a plague upon society!”

Sentence= “Boy Bands are ” & “TheAnswer”Sentence= “Boy Bands are ” & “TheAnswer” Sentence= “Boy Bands are ” & TheAnswerSentence= “Boy Bands are ” & TheAnswer

SpacingSpacing

Spacing: Does not insert spaces for youSpacing: Does not insert spaces for you– ““This is” & “not right” This is” & “not right”

This isnot rightThis isnot right– ““This is ” & “right” This is ” & “right”

This is rightThis is right Space itself has an ASCII code, Space itself has an ASCII code, which is 32 (10 base), or 00100000 which is 32 (10 base), or 00100000 (binary)(binary)

String RelationshipsString Relationships

String can be compared.String can be compared. StringA = StringB : comparing if two string StringA = StringB : comparing if two string

is identical.is identical. StringA <> StringB : different fromStringA <> StringB : different from

– ““Hello” <> “hello” is true.Hello” <> “hello” is true. StringA < StringB : if the string A will StringA < StringB : if the string A will

appear earlier in a dictionary than B.appear earlier in a dictionary than B. >, <=, >=>, <=, >=

String FunctionsString Functions

Functions are built in processes that do Functions are built in processes that do something to a variable or piece of something to a variable or piece of informationinformation

Functions have Functions have ARGUMENTSARGUMENTS, or values , or values that you put into themthat you put into them

ARGUMENTS go inside parenthesesARGUMENTS go inside parentheses Left(“fanatic”, 3) Left(“fanatic”, 3) Left(fanatic, 3)Left(fanatic, 3)

String FunctionsString Functions

Len(string) – finds lengthLen(string) – finds length Left(string, n) takes left most Left(string, n) takes left most nn characterscharacters Right(string, n) does same from rightRight(string, n) does same from right Ucase(string) makes string UPPERCASEUcase(string) makes string UPPERCASE Trim(string) – takes spaces off endsTrim(string) – takes spaces off ends Mid(string, start, length) – takes a string from Mid(string, start, length) – takes a string from

middle (great for dividing strings up into pieces)middle (great for dividing strings up into pieces) InStr(string, substring) searches for substring in InStr(string, substring) searches for substring in

stringstring

Mid StringMid String

DNA=“ACGTGACACTGAC”DNA=“ACGTGACACTGAC” Base1=Mid(DNA, 1, 1)Base1=Mid(DNA, 1, 1) “A” “A” Base2=Mid(DNA, 2, Base2=Mid(DNA, 2, 44)) “CGTG” “CGTG”

..

..

.. Base6=Mid(DNA, 6, Base6=Mid(DNA, 6, 22)) “AC” “AC”

InStrInStr()() – In String – In String

DNA=“ACGTGACACTGAC”DNA=“ACGTGACACTGAC” Location=InStr(DNA, “CACTG”)Location=InStr(DNA, “CACTG”)

Returns location of first character of substringReturns location of first character of substring

Working with Text StringsWorking with Text Strings

Comparison = means “Comparison = means “identical toidentical to”” ““yes” is not equal to “Yes”yes” is not equal to “Yes” ““yes “ is not equal to “yes”yes “ is not equal to “yes” Prepare strings for comparisonPrepare strings for comparison

– answer = Ucase(answer) answer = Ucase(answer) – makes it all caps– makes it all caps– answer = Trim(answer) answer = Trim(answer) – takes off spaces– takes off spaces

Then, compare to all caps!Then, compare to all caps! – if answer = “YES” thenif answer = “YES” then

Numeric FunctionsNumeric Functions

answer = Sqr(varNum)answer = Sqr(varNum)

answer = Int(varNum)answer = Int(varNum) – – truncatestruncates (cuts (cuts off decimal stuff) and makes integer off decimal stuff) and makes integer Int(3.7) Int(3.7) 3 3

Int(-2.34) Int(-2.34) -2 -2

answer= Round(varNum)answer= Round(varNum) – rounds number – rounds number

Round(3.7)Round(3.7) 4 4

ProceduresProcedures

String and numeric functions belong to a String and numeric functions belong to a VB category called “procedure”VB category called “procedure”

Procedures are pre-defined code fragments.Procedures are pre-defined code fragments. There are three types of procedures.There are three types of procedures.

– Event procedure (event handler)Event procedure (event handler)– General procedureGeneral procedure– Function procedureFunction procedure

Event ProcedureEvent Procedure

Event procedure is also called event handler.Event procedure is also called event handler. It is associated with an event of the object.It is associated with an event of the object. The name of a event procedure is specially The name of a event procedure is specially

structured.structured.Private Sub ObjectName_EventName()Private Sub ObjectName_EventName()

……

End SubEnd Sub Underscore

General ProceduresGeneral Procedures

Defined by key word Defined by key word Sub Sub Private Sub ProcedureName()Private Sub ProcedureName()

Block of codeBlock of code

End SubEnd Sub Not linked with any eventNot linked with any event Can be called by other part of code.Can be called by other part of code.

– Call ProcedureName()Call ProcedureName()

Why using general procedures?Why using general procedures?

Making the code clear and well structured.Making the code clear and well structured.– Rule of coding #1: Don’t write a procedure that Rule of coding #1: Don’t write a procedure that

is more than 50 lines long.is more than 50 lines long. Distinguishing different function blocks.Distinguishing different function blocks. Reusing the repetitive code Reusing the repetitive code

Passing arguments to a procedurePassing arguments to a procedure

AnalogyAnalogy– Inputs for a computer is as :Inputs for a computer is as :– Arguments for a procedure.Arguments for a procedure.

DefinationDefinationPrivate Sub ProcedureName(arg1 as type, Private Sub ProcedureName(arg1 as type, arg2 as type)arg2 as type)Block of codeBlock of code

End SubEnd Sub In the code section that calls itIn the code section that calls it

Call ProcedureName(arg1, arg2)Call ProcedureName(arg1, arg2)

A computer without a output device?A computer without a output device?

A sub procedure is like a computer that A sub procedure is like a computer that only has input device.only has input device.

Although you can display result on the Although you can display result on the screen, other output devices are definitely screen, other output devices are definitely helpful.helpful.

Therefore we need another kind of Therefore we need another kind of procedure --- function procedure.procedure --- function procedure.

Functions procedureFunctions procedure

Function is a sub procedure with a returned value.Function is a sub procedure with a returned value. Function procedure is used in the same way as a Function procedure is used in the same way as a

built-in numeric or string function.built-in numeric or string function.Variable = FunctionName(arguments…)Variable = FunctionName(arguments…)

Define a functionDefine a functionPrivate Function FunctionName(arg1 As Private Function FunctionName(arg1 As type1, arg2 As type2,…) As ReturnTypetype1, arg2 As type2,…) As ReturnType

Block of codeBlock of codeFunctionName=expressionFunctionName=expressionEnd FunctionEnd Function

HomeworkHomework

Read book page 97-110Read book page 97-110 Lots of useful information in the comments Lots of useful information in the comments

section of the book.section of the book. Today’s office hours are rescheduled to Today’s office hours are rescheduled to

Wednesday 1:30-3:30 Wednesday 1:30-3:30 only for this weekonly for this week..