Solved

# how to separate the float number from string

Posted on 2008-10-30
Medium Priority
362 Views
Hello Guys,
Can you tell me how can I receive only a float number from the string. For example:
string -  252.676g or f466.422d
BR
Vaalar
0
Question by:Vaalar
• 7
• 3
• 3

LVL 38

Accepted Solution

Geert Gruwez earned 1600 total points
ID: 22840148
use the Val function

function ConvertFloat(aText: string): Double;
var S: string;
I, aCode: Integer;
begin
// First delete all non number characters
I := 1;
while (I < Length(aText)) and not (aText[I] in ['-','+',DecimalSeparator,ThousandSeparator,'0'..'9']) do
Inc(I);
// Convert text to float
Val(Copy(Atext, I, Length(aText)), Result, aCode);
end;
0

LVL 15

Assisted Solution

mikelittlewood earned 400 total points
ID: 22840218
This assumes only one number in there
I use the tryTo function instead of the val

function TForm1.returnFloat(const s: string): double;
var
i: integer;
temp: string;
begin
result := 0;
temp := '';
for i := 0 to length( s) do
if s[i] in ['0'..'9', DecimalSeparator,ThousandSeparator, '+', '-'] then
temp := temp + s[i];

if temp <> '' then
tryStrToFloat( temp, result)
end;
0

LVL 15

Expert Comment

ID: 22840268
Geert_Gruwez, your code doesnt take into account if there is a non numerical character at the end of the string.
0

LVL 38

Expert Comment

ID: 22840278
no need the Val does this
0

LVL 38

Expert Comment

ID: 22840294
the aCode will show the location of the problem

maybe Vaalar can evaluate further what he wants to happen ?
0

LVL 15

Expert Comment

ID: 22840334
In fact it might be better to make sure you never continue past the first number that is found

function TForm1.returnFloat(const s: string): double;
var
i, startPos, endPos: integer;
begin
result := 0;

startPos := 1;
while ( not ( s[ startPos] in ['0'..'9', DecimalSeparator,ThousandSeparator, '+', '-'])) and
( startPos <= length( s)) do
inc( startPos);

endPos := startPos;
while ( s[ endPos] in ['0'..'9', DecimalSeparator,ThousandSeparator, '+', '-']) and
( endPos <= length( s)) do
inc( endPos);

if endPos >= startPos then
tryStrToFloat( copy( s, startPos, endPos - startPos), result)
end;
0

Author Comment

ID: 22840744
I have tested your ideas and it solves  but if i have for example 244e.322 i get 244 afer using Gerts solution. I need to receive 244.322.
The same problem comes out in Mikes solution.
0

Author Comment

ID: 22840760
I have tested your ideas and it solves some problems  but if i have for example 244e.322 i get 244 afer using Gerts solution. I need to receive 244.322.
The same problem comes out in Mikes solution.
0

LVL 38

Expert Comment

ID: 22840976
you could first strip all non numerals:

function ConvertFloat(aText: string): Double;
var S: string;
I, aCode: Integer;
begin
// First delete all non number characters
I := 1;
s := '';
while (I <= Length(aText)) and (aText[I] in ['-','+',DecimalSeparator,ThousandSeparator,'0'..'9']) do
begin
s := s + aText[I];
Inc(I);
end;
// Convert text to float
Val(S, Result, aCode);
end;
0

LVL 38

Expert Comment

ID: 22841015
this will never solve all problems
it will get the first number possible

but to resolve this you'll need to specify some rules:

aText := 'abc123.def456-789+1023xxx';

Value to string = '123.456-789+1023';
0

LVL 38

Expert Comment

ID: 22841022
woops slight mistake

function ConvertFloat(aText: string): Double;
var S: string;
I, aCode: Integer;
begin
// First delete all non number characters
I := 1;
s := '';
while (I <= Length(aText)) do
begin
if (aText[I] in ['-','+',DecimalSeparator,ThousandSeparator,'0'..'9']) then
s := s + aText[I];
Inc(I);
end;
// Convert text to float
Val(S, Result, aCode);
end;
0

LVL 38

Expert Comment

ID: 22841052
or try StrToFloatDef

Result := StrToFloatDef(S, 0);
0

Author Comment

ID: 22841236
Thank you very much Geert,
and thx also to Mike
BR
Vaalar
0

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