script that can handle exponentials

[Marc Ahrendt]

any tricks in perl or ksh to take an input value, for example, 7.00E-5, and multiply it by a similar value?

basically i am writing a very simple calculator for some engineers here but have no idea on how to add, subtract, multiply, etc.. values in the format 8.03e-3

in the past i have used "bc" but not sure if there was an elegant way of working with exponents like this

[Chris Vail]

bc is the catch-all executable for all of these kinds of things. I find it quite elegant, actually. The korn shell itself has very limited math capability. Its limited to the "let" statement--denoted with double parens: (( and )).

I don't do perl, but suspect that it too uses bc.


Chris

[A. Clay Stephenson · Accepted solution]

Perl natively understands exponential notation and can easily output in the same or in the floating point output format of your choice. Normally Perl does all math in floating-point and you have to tell it explicitly (via "use integer;") to do integer math.

#!/usr/bin/perl

my $a = 7.00e-5;
my $b = 2000.0
my $c = $a * $b;
printf("Fixed point: %10.2f Exponential: %e\n",$c,$c);

[Biswajit Tripathy]

If you want to multiply, say 7.00e-5 with 5.00e2,
then you do something like this:

----
#!/usr/bin/ksh
a="7.00*e(-5)"
b="5.00*e(2)"
echo "a=($a)*($b)" | bc -l
----

Basically, you need to take the user input and
format it to a string like 'a' and 'b' as shown
above. See bc(1) manpages for all the cool maths
things you can do.

- Biswajit

[Biswajit Tripathy]

Sorry for the typo in my last post. Change the
script to:

---
#!/usr/bin/ksh
a="7.00*e(-5)"
b="5.00*e(2)"
echo "($a)*($b)" | bc -l
---

- Biswajit

[Marc Ahrendt]

thx ...the quick feedback was very helpful