## Basic arithmetic operation with awk?

 beginners Basic arithmetic operation with awk?
Basic arithmetic operation with awk?

input:
Output:
Basically I am trying to calculate the result of "the path" in \$3 where the operators follow the number and not preceding them like we normally do:
rec_10: +1+2-2=1

But I realise (I am sure there is a good reason for that) that awk does handle basic arithmetic operations, like:
(+1) + (2) + (-2) = 1
Giving that to awk:
makes it stuck in a loop.

Therefore, I think the approach of putting the numbers and operators in the right order (code below) would not work at the end anyway:
output:
Is there any awk trick I could use instead?
Maybe using an increment x++, but instead of the '+' sign writing some variables like for example:
The code above is just an example and returns:

Last edited by beca123456; 12-18-2015 at 10:51 PM..
 beca123456 View Public Profile for beca123456 Find all posts by beca123456
Is this a homework assignment? (Homework and coursework questions can only be posted in the Homework & Coursework forum with a completely filled out template from the special homework rules described here.)

I have no idea what you are trying to do. Arithmetic operators (except unary minus) work on two operands. Therefore, a arithmetic formula has one more operand than there are operators. But, your example has 3 operands and 3 operators.

Are you saying that you want each number to have a trailing + or - sign to indicate whether the number is positive or negative and you then want to add up all of the signed numbers?

Are you only processing single-digit numbers?
 Don Cragun View Public Profile for Don Cragun Find all posts by Don Cragun
No, it has been a long time I left school (I should have probably taken more programming classes though).

Long story short. I have a string like this:
Which actually defines 3 numbers (written in the usual format below):
I am trying to get the result of the sum of these numbers:
(+1) + (+2) + (-1)
Which is equal to:
1+2-1=2

The + or - signs are actually not operators. They tell you if the number before the sign is positive or negative.

Another example:
Should returns:
Because:
(+10) + (-12) + (+8) + (+4)
= 10 - 12 + 8 + 4
=10

I recognize this format is pretty unusual.

Last edited by beca123456; 12-19-2015 at 01:32 AM..
 beca123456 View Public Profile for beca123456 Find all posts by beca123456
Quote:
Originally Posted by beca123456
... ... ...
The code above is just an example and returns:
I am having trouble following the logic of your script.

The diagnostic you are getting is because the sequence x(i) is a request to call the function named x with the parameter i, you haven't defined any functions, and the function x is not one that is defined by gawk. Furthermore, you can't have a variable and a function with the same name.

Note that the statement: x==0; is a logical expression (not an assignment statement) returning the value 1 if the variable x is zero or an empty string; otherwise it returns 0. (Note that the value of that logical expression doesn't affect the behavior of this script in any way; it does not assign a value to x.)

Although the gawk statement:
splits the 2nd input field into the array b[] with each element of b[] being set to one character from that field and sets a to the number of characters found; using an empty string as an ERE specifying the field delimiter is not available in all versions of awk (including the one I am using on OS X).

You might want to try something more like:
which, if file contains:
produces the output:
This was tested using awk on OS X, but should also work with gawk on any Linux system.

If someone wants to try this script on a Solaris/SunOS system, change awk to /usr/xpg4/bin/awk or nawk.
This User Gave Thanks to Don Cragun For This Post:
 Don Cragun View Public Profile for Don Cragun Find all posts by Don Cragun
Different approach, not sure if better/faster:
These 2 Users Gave Thanks to RudiC For This Post:
 RudiC View Public Profile for RudiC Find all posts by RudiC
Quote:
Originally Posted by RudiC
Different approach, not sure if better/faster:
This is a nice approach, and works fine with gawk and other awk implementations that use FS="" to split each input character into a field. A similar approach that doesn't depend on this behavior (which the standards say produces unspecified results) would be:
which also has a little feature creep allowing a decimal point to be included in the input numbers (sparked by RudiC's code using %f instead of %d in the sprintf() format string).

If you change:
in RudiC's script to:
his script will also handle floating point values in awk versions where:
doesn't produce a syntax error.
This User Gave Thanks to Don Cragun For This Post:
 Don Cragun View Public Profile for Don Cragun Find all posts by Don Cragun
The problem reminds me of a rudimentary RPN calculator that I recently did. As it expects operands and operators in separate fields, I added a gsub with spaces at the begin of each step: ( and, in principle, it would need a 0 operand in the beginning. It uses the "|" now resulting in a zero value to start with)
 RudiC View Public Profile for RudiC Find all posts by RudiC

Test Your Knowledge in Computers #907
Difficulty: Easy
The Unix shell command line is a sequence of ASCII text words delimited by curly braces.
True or False?

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