# how to calculate

I would like to do some calculations on my form.
I have dbtext,currencyedit's and dbedit's.
Can you give me example how to calculate using these?
example:
I have a dbtext that gets a value from database.
Now I want that value to divide from a value in editbox
so a currency edit gives me the right sum..
just learning...
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Commented:
var a, b: Integer;
c: Double;

if TryStrToInt(dbtext.caption, a) and tryToInt(dbedit.text, b) then
c := b / a;

ziolko.
0
Author Commented:
dont understand a thing...
I tried --
var a, b: Integer;
c: Double;
begin
if StrToInt(dbedit1.text, a) and StrToInt(edit14.text, b) then
currencyedit37.value := b / a;

and it dont work...please fro a nice explanation as I just learn
0
Author Commented:
if TryStrToInt(dbedit1.Text,a) and TryStrToInt(edit14.text,b) then
currencyedit37.value:= a / b;
does not work either...
0
Commented:
TDBEdit has property called Text
TDBEdit has property called Caption
both properties are of type string which means they can contain literlas
so if you want to do any mth calculation you need to convert them

there are 3 most commonly used functions:
1. StrToInt() this func will throw exception if it's not possible to convert
sample

procedure S1;
var s: string;
i: Integer;
begin
s := 'hello world';
try
StrToInt(s, i);
except
ShowMessage('cannot convert hello world to integer value');
end;
end;

2. TryStrToInt() <- no error will be thrown

procedure S2;
var s: string;
i: Integer;
begin
s := 'hello world';
if not TryStrToInt(s, i) then
ShowMessage('cannot convert hello world to integer value');
end;

3. Val() <- no error will be thrown

procedure S3;
var s: string;
i: Integer;
val: Integer;
begin
s := 'hello world';
Val(s, i, code);
if code <> 0 then
ShowMessage('cannot convert hello world to integer value');
end;

ziolko.
0
Commented:
what kind of values you have in edits?

ziolko.
0
Author Commented:
dbedit has no caption value but text.
in your 1st example to what do I assign   'c' ??
My 'c' should be a currency edit...
0
Author Commented:
in edits I have numbers only...
0
Commented:
my mistake TBText has Caption...

this should work unless you have floating point values in edit or text
if TryStrToInt(dbedit1.Text,a) and TryStrToInt(edit14.text,b) then
currencyedit37.value:= a / b;

if you have floating point use TryStrToFloat()

ziolko.
0
Author Commented:
dbedit1 is currency value in the database.
in edit14 i type in (freehand) number values.
I tried (on exit of the edit14):
procedure TPostavke.Edit14Exit(Sender: TObject);
var a, b: Integer;
c: Double;
begin
if TryStrToInt(dbedit1.Text,a) and TryStrToInt(edit14.text,b) then
currencyedit37.value:= a / b;
end;
It does not work..
If i substitute TryStrToInt with TryStrToFloat i get :
[Error] Unit3.pas(255): There is no overloaded version of 'TryStrToFloat' that can be called with these arguments

You see I have a value of '584,65 €' in my dbedit1.
Now I want to type (example number 2 in my editbox) and when I leave the edit my currency displays
292,325...
0
Commented:
ok,

procedure TPostavke.Edit14Exit(Sender: TObject);
var a: Currency;
b: Double;
begin
if TryStrToCurr(dbedit1.Text,a) and TryStrToInt(edit14.text,b) then
currencyedit37.value:= a / b;
end;

ziolko.
0

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Author Commented:
procedure TPostavke.Edit14Change(Sender: TObject);
var a: Currency;
b: double;
begin
if TryStrToCurr(dbedit1.Text,a) and TryStrToInt(edit14.text,b) then
currencyedit37.value:= a / b;
end

I get :
[Error] Unit3.pas(256): Types of actual and formal var parameters must be identical
0
Commented:
0
Commented:
what the ...??

if TryStrToCurr(dbedit1.Text,a) and TryStrToFloat(edit14.text,b) then
currencyedit37.value:= a / b;

where did it go??

ziolko.
0
Author Commented:
Dont seem to work...both ways...
0
Author Commented:
I think i have figured what is the mistake here..
a queery that is the info provider for dbedit1 has the field
marked as 'currency' (it is currency in the database however)
But when I remove the field type as 'currency' in the
field rooster and set it to currency false the code :
var a: Currency;
b: integer;
begin
if TryStrToCurr(dbedit1.Text,a) and TryStrToInt(edit12.text,b) then
currencyedit37.value:= a / b;
works !
is this ok ??
0
Commented:
if it works it's ok:)

ziolko.
0
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