How to convert float to string in Delphi specifying Significant Digits, not Decimal Digits (and not G format)

Question

I usually print numbers with a specific number of decimal digits, but I now need to print one with a specified number of significant digits. The numbers need to be like "1.23" not like "1.2 E0". I see that Delphi will do the latter with the G format, but I cannot see how to do this in the former format.

How do you _print_ the numbers? show some code! – jachguate Jan 11 '13 at 09:24 — jachguate, Jan 11 '13 at 09:24

score 3 · Answer 1 · answered Feb 27 '14 at 15:31

3

Use Format:

Format('%.3g',[Value]));

The 'g' specifies significant figures, I'll let you work out what the 3 means...

answered Feb 27 '14 at 15:31

Steve Magness

863
14
25

score 0 · Answer 2 · answered Jun 10 '13 at 15:40

0

FormatFloat('0.000', YourFloatNumber)

Use as many zeros as you would need to represent the digits.

answered Jun 10 '13 at 15:40

gustavogbc

695
11
33

1

'significant digits' does not specify a fixed number of decimals. Here's a link if you'd like to learn more: https://en.wikipedia.org/wiki/Significant_figures – Bjarke Moholt Oct 04 '15 at 13:06

score 0 · Answer 3 · answered Jun 12 '23 at 10:04

Format('%.2g', MyNumber) => limit the output to 2 decimals
FormatFloat('0.00', MyNumber) => force exactly 2 decimals

Example:

MyNumber1 := 2
MyNumber2 := 3.8
MyNumber3 := 4.97

WriteLn(Format('Variant 1: %.2g / %.2g / %.2g', [MyNumber1, MyNumber2, MyNumber3]));
WriteLn(Format('Variant 2: %s / %s / %s', [FormatFloat('0.00', MyNumber1), FormatFloat('0.00', MyNumber2), FormatFloat('0.00', MyNumber3)]));

Output:

Variant 1: 2 / 3.8 / 4.97
Variant 2: 2.00 / 3.80 / 4.97

How to convert float to string in Delphi specifying Significant Digits, not Decimal Digits (and not G format)

3 Answers3