string to literal conversion

[codemut]

Based on this code...

BEGIN {
str = "2+2"
split(str,arr,"")
print arr[1] arr[2] arr[3]
}

...how can one simply convert the string arr[2] to the + math operator so as to print 4?

 

[Annihilannic]

Unless you want to implement a complete mathematical expression interpreter (which could be easy or difficult, depending on how complex you want the expression support to be) you could simply pass the expression to an external utility which is designed to do that job already, e.g. bc.

awk '
        BEGIN {
                str="2+2"
                "echo " str " | bc " | getline result
                print result
        }
'

Annihilannic.

 

[feherke]

Hi

Or we can stay with [tt]awk[/tt] : ;-)

awk '
        BEGIN {
                str="2+2"
                "[highlight]awk \"BEGIN{print[/highlight] " str "[highlight]}\"[/highlight]" | getline result
                print result
        }
'

Feherke.

http://rootshell.be/~feherke/

 

[codemut]

Thanks so far ... but plucking out the '+' is key. If only there was something like strtonum(arr[2]) to force '+' to function.

 

[Annihilannic]

If only.

Annihilannic.