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Full Discussion: Can expr deal with decimals?
Top Forums Shell Programming and Scripting Can expr deal with decimals? Post 302744105 by hxdrummerxc on Thursday 13th of December 2012 11:01:59 PM
Old 12-14-2012
Can expr deal with decimals?
Hello,
Im trying to work on a small script for a formula converting temperatures, Celsius to fahrenheit.

I have a formula, and it works.... it works every way I try it. But it keeps giving me the wrong results every time with expr.

The formula for C to F would be:
divide by 5, multiply by 9, add 32.

So..... simple code here
Code:
read c
f= `expr $c / 5 \* 9 + 32`
echo $f

The problem is, its never correct because expr can't seem to add the decimals right.

For instance 32 degrees celcius.
f=`expr 32 / 5 \* 9 + 32` gives me 86 for some reason. It should give 89 (or 89.6)

I have also tried it another way, which seems odd, but still should give correct results.
Code:
f=`expr 9 / 5 \* $c + 32`

Again, I have tested, it should be 89, but it ends up giving me 64.


Because expr 9 / 5 is giving me 1, instead of 1.8
So 1 * 32 = 32 + 32 = 64.
It should be 1.8 * 32 = 57.6 + 32 = 89.6

It seems like my problem is the fact that expr won't account for decimals.
Is there a way to get it to acknowledge the decimals?
Or is this not possible with the expr command?

Thanks a lot
Last edited by Scrutinizer; 12-14-2012 at 01:20 AM.. Reason: code tags
 

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LEARN ABOUT DEBIAN

device::usb::pcsensor::hidtemper::sensor

Device::USB::PCSensor::HidTEMPer::Sensor(3pm)		User Contributed Perl Documentation	     Device::USB::PCSensor::HidTEMPer::Sensor(3pm)

       Device::USB::PCSensor::HidTEMPer::Sensor - Generic sensor class

VERSION

       Version 0.02

SYNOPSIS

       None

DESCRIPTION

       This module contains a generic class that all HidTEMPer sensors should inherit from keeping the implemented methods consistent, and making
       it possible to use the same code to contact every supported device.

   CONSTANTS
       o  MAX_TEMPERATURE

	  The highest temperature(Celsius) this sensor can detect.

       o  MIN_TEMPERATURE

	  The lowest temperature(Celsius) this sensor can detect.

   METHODS
       o  new( $device )

	  Generic initializing method, creating a sensor object.

	  Input parameter

	  $device = A pre-initialized Device::USB::PCSensor::HidTEMPer::Device that the sensor is connected to. This device will be used to handle
	  communication.

       o  fahrenheit()

	  Reads the current temperature and returns the corresponding value in fahrenheit degrees.

       o  max()

	  Returns the highest temperature(Celsius) the sensor can detect.

       o  min()

	  Returns the lowest temperature(Celsius) the sensor can detect.

       o  celsius()

	  Empty method that should be implemented in each sensor, returing the current degrees in celsius.

DEPENDENCIES

       This module internally includes and takes use of the following packages:

	 use Scalar::Util qw/ weaken /;

       This module uses the strict and warning pragmas.

BUGS

       Please report any bugs or missing features using the CPAN RT tool.

FOR MORE INFORMATION

       None

AUTHOR

       Magnus Sulland < msulland@cpan.org >

ACKNOWLEDGEMENTS

       None

COPYRIGHT &; LICENSE
       Copyright (c) 2010 Magnus Sulland

       This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

perl v5.10.1							    2010-07-24			     Device::USB::PCSensor::HidTEMPer::Sensor(3pm)
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