CODEWITHSUNDEEP
perlprintf
David B
David B

Reputation: 29998

How to control floating-point formatting in Perl using sprintf?

I usually use %g, but it seems the number of exponent digits is system-dependent, and I can't variants like %.4g or %.2g to work (they simply produce the same results, don't they?).

What I actually would like to do is to use simple floating point representation "when possible" if the number (in absolute value) is in some range (e.g. 10^5 > |x| > 10^-5), otherwise use scientific notation. I also want to limit the number of digits displayed to, say, 5 (so I won't get super huge floating point numbers like 0.12345678901234567890...).

Some examples:

0.123456890 -> 0.12346

0.000000000123456 -> 1.23456e-10

Can I do that directly in sprintf or do I have to write a special wrapper?

Upvotes: 1

Views: 797

Answers (1)

cjm
cjm

Reputation: 62109

No, you'd have to write a custom wrapper to get the behavior you describe: As perlfunc says:

For "g" and "G", [the precision] specifies the maximum number of digits to show, including those prior to the decimal point and those after it;

Note that leading zeros in the simple floating point representation are not counted as "digits".

There are some modules on CPAN that'll help you write a sprintf-like function. String::Sprintf is for adding a custom format or two to the regular sprintf formats. String::Formatter is for starting from scratch with a function that looks like sprintf but doesn't inherit any formats from it.

Upvotes: 4

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