lesson 2.4 random numbers and built-in functions

8/19/2019 Lesson 2.4 Random Numbers and Built-In Functions

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Lesson 2.4

Random Numbersand Built-InFunctions


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Objectives

!t t"e end o# t"e lesson$ %ou s"ouldbe able to

&. describe t"e utilit% o# some o#

'B(s built-in #unctions2. evaluate e)*ressions t"at use

t"ese #unctions+ and

,. enerate random numbers.


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/"e eneration o# random

numbers is too im*ortant to bele#t to c"ance0. 1R. Cove%ou

-One o# t"e assets o# 'B is its abilit%

to enerate random numbers.Randomness is im*ortant in

com*uter amin as %ou ma% "ave

e)*erienced. /"ere is not"in

orse t"an a *redictable ame !I.O# course$ randomness needs to be

controlled.


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! 3uessin 3ame

Let us construct a ame "ereint"e user tries to uess a number

"eld b% t"e com*uter. /o "el* t"e

user$ t"e com*uter s"ould *rom*t

t"e user to mae a loer or a"i"er uess i# "is5"er uess is

incorrect. 6e s"all need a #orm

it" a te)t bo) namedtxtGuess

and a command button named

cmdOk$ "ose code ill loo

somet"in lie t"is


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7im 3uess !s Inteer

7im Remar !s Strin

Const Number !s Inteer 8 ,9

:rivate Sub cmdO;Clic


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?lseI# 3uess @ Number /"en

Remar 8 AI3A?R0

?lse

Remar 8 RI3A/0

?nd I#

sBo) Remar$ 4$ Simon Sa%s0

?nd Sub


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! 3uessin 3ame

Dou "ave *robabl% noticedsomet"in else-t"e sBo)

statement. /"e sBo)

statement *roduces a *o*-u*

messae bo) t"at *rom*ts t"e

user to clic on a command

button


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!natom% o# a essae Bo)

sBo) message, style, title

/"e messae is t"at "ic" a**ears

in t"e messae bo)


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For t"e buttons

VALU E

NAME

D

CONS

TANT

BUTT ONS

DISPL

AYED

0 vbOk Only

Okbutton

1vbOk Canc el

Ok

andCancelbutton

continuationE



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For t"e icon

continuationE


Val ue

Name

d

Const

ant

Icon

1) vbC"*t *cal

&! vb+u

et*on

(, vbE-c la.at*

on

)( vbIn/


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For e)am*le$ %ou ant Des andNo buttons to a**ear toet"er

it" t"e critical icon$ let st%le be

t"e sum o# t"e values


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Note t"at %ou can include in %ourcode actions t"at de*end on t"e

command button cliced in t"e

messae bo)$ but t"at is u* to %ou to

e)*lore.

continuationE



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Construct t"e uessin ame *roram

e(ve just discussed. 'eri#% i# it ors.

Try this on your computer:

continuationE



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3eneratin a Random Number

Dou ma% "ave noticed to t"ins entron it" our *roram. One is t"at as

user can onl% *la% t"is ame once


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Fortunatel%$ 'B "as somet"in t"at can"el* a *seudo variable called Rnd. Rnd is

a variable in t"e sense t"at it re*resents

a value$ but unlie a real variable$ t"at

value c"anes eac" time %ou re#er to it.

continuationE


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Construct a #orm it" a te)t bo)

named t)tOut*ut and a command

button called cmd3enerate. /o t"ecommand button$ assin t"e

#olloin code.

Sub cmd3enerate;Clic< =

t)tOut*ut./e)t 8 Rnd

?nd Sub

Try this on your computer:

continuationE



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i i


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6e can no enerate numbers beteen G and&G but "at e reall% need #or t"e uessin

ame *roram are "ole numbers. In comes a

built-in #unction called Fi). Fi) dro*s t"e

decimal *ortion o# a number suc" t"atFi)


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Note t"at e can no enerate randominteers #rom G to 9. 6"at i# e ant

numbers #rom & to &GJ /"e solution is

sim*le.

Sub cmd3enerate;Clic


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Note t"at$ in eneral$ Fi)


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Un#ortunatel%$ it seems t"at our *roramenerates t"e same set o# random

numbers. /"e reason is somet"in called

a random number seed or random seed.

Imaine our com*uter standin at t"eede o# a *ool o# random numbers. I# t"e

com*uter ere to stand in t"e same

s*ot$ it ould be ettin t"e same set o#numbers. /"e random seed dictates

"ere around t"e *ool t"e com*uter

s"ould stand.

continuationE


ti ti


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/"e *roblem is t"at e need t"atrandom seed to be di##erent ever% time

e run t"e *roram. So$ "at c"anes

ever% time e run t"e *roramJ /ime

continuationE


ti ti


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6e need to et t"e random seed #romt"e internal cloc o# t"e com*uter. /"e

statement #or t"at is as #ollos

continuationE


Sub cmd3enerate;Clic< =

RandomiMe /imer

t)tOut*ut./e)t 8 Fi)


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6e are no read% to mae t"e uessiname *roram more #un. Su**ose e

ant t"e number to be uessed to be

#rom & to &GG. O# course t"is reuires

t"e e)*ression Fi)


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:lacin it it"in t"e cmdO;clic


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:rivate Sub Form ;


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So #ar e(ve been introduced to too# 'B(s built 1in #unctions. /"ese

are 'al and Fi). Recall t"at 'al


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Ot"er Built-in Functionsunct*o

n

Dec"*t*on

Ab2N3

4et t5eabolutevalue o/ N

E-' Ab2&3 6 Ab27&3 6 &

Int2N3

#ound do8nN to t5enea"et*nte$e" 96N'E-' Int21'!3 6Int213 6Int21':3 6 1

Int271')3 6 Int27 1'1 6 Int 7! 6

continuationE

continuation


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Remember t"at t"ese #unctions canbe used in conjunction it"

arit"metic o*erators. For e)am*le$

consider t"e uadratic #ormula t"at#ollos

Ot"er Built-in Functions

continuationE

continuation


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O# course$ e do not "ave ano*erator lie so in code e need

to lines


continuationE

)& 8


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/"ese are called numeric #unctionsbecause t"e% result in numeric

values. 'B also o##ers us several

#unctions t"at result in strinvalues.


continuationE


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Some Built-in Strin Functionsu nct

*on

Dec"*t*on

LC ae

2St "*n$3

Conve"t t5et"*n$>c5a"acte" to

lo8e"cae'E-'LCae2?Bob@36 ?bob@

LCae2?BOB@36 ?bob@ Lcae2?bob@36 ?bob@

UC Conve"t t5e

continuation


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Lcase and Ucase are *articularl%

use#ul in *rorams reuirin te)tin*ut. For e)am*le$ consider t"e

Branc"es o# 3overnment *roram in

Lesson 2.2.

continuationE

Some Built-in Strin Functions


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continuationE

l


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Notice t"at i# %ou enter PU7ICI!L or

Pudicial$ it ill #ail to dis*la% Su*remeCourt. /"e *roram is case-sensitive

/o mae it case-insensitive$ *rocess

t"e user(s in*ut to matc" t"e o*tion.In t"is case Lcase is t"e e%.

continuationE

Some Built-in Strin Functions


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lesson 2.4 random numbers and built-in functions

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