CODEWITHSUNDEEP
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ILovePolitics
ILovePolitics

Reputation: 23

Can I prevent GNU bc from spewing out zeros?

Suppose I want to solve the equation x + 3 = 40 using GNU bc. One way I could do this would be to start by checking to see if 0 is a solution, then checking 1, and so on, until I get to the right answer. (Obviously not the best way to do algebra, but oh well.) So I enter the following code into GNU bc:

int solver(int x);
define solver(x){
if(x + 3 == 40) return x;
x = x + 1;
solver(x)
}
solver(0)

It produces 37 - the right answer, of course - but the 37 is then followed by 37 zeros. Based on some experimentation, it seems like each zero comes from an instance of the if statement being false, but how do I prevent the zeros from showing up? I'm using GNU bc to solve more complicated functions and create more complex lists of numbers, so it really isn't practical for me to sort through all the zeros. Any help would be appreciated, since I haven't yet figured anything out.

Upvotes: 2

Views: 158

Answers (1)

Benjamin W.
Benjamin W.

Reputation: 52291

For each operation that isn't an assignment, bc prints an exit status. One way to suppress that is to assign to the dummy value . (which is just the value of the last result anyway), another way is to make sure you explicitly print exactly what you need.

I would have written your function like this:

#!/usr/bin/bc -q

define solver(x) {
    if (x + 3 == 40) return x
    return solver(x+1)
}
print solver(0), "\n"

quit

A few remarks for your attempt:

  • I don't understand what your first line is supposed to do, I just dropped it
  • I've indented the code, added some whitespace and removed the semicolons – mostly a matter of taste and readability
  • I've simplified the recursive call to avoid the solver(x) line stand on its own, as this produces the spurious 0

As for your suspicion that the if statement produces the zeroes: try, in an interactive session, the following:

1 == 2                      # Equality test on its own produces output
0
1 == 1                      # ... for both true and false statements
1
if (1 == 2) print "yes\n"   # No output from false if condition
if (1 == 1) print "yes\n"   # If statement is true, print string
yes

Upvotes: 1

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