R Bisection Method

Implementation of Bisection Method written in R.

Enter beginning of interval: 0
Enter end of interval: 2
Enter precision: 0.0000001
X:  1
X:  0.5
X:  0.25
X:  0.375
X:  0.4375
X:  0.40625
X:  0.421875
X:  0.4140625
X:  0.41796875
X:  0.416015625
X:  0.4150390625
X:  0.41455078125
X:  0.414306640625
X:  0.4141845703125
X:  0.41424560546875
X:  0.414215087890625
X:  0.414199829101562
X:  0.414207458496094
X:  0.414211273193359
X:  0.414213180541992
X:  0.414214134216309
X:  0.41421365737915
X:  0.414213418960571
X:  0.414213538169861
X:  0.414213597774506

# ? 2018 TheFlyingKeyboard and released under MIT License
# theflyingkeyboard.net

f <- function(x) {
  return(x * (x + 2) - 1)
}	

intervalBegin <- as.double(readline(prompt = "Enter beginning of interval: "))
intervalEnd <- as.double(readline(prompt = "Enter end of interval: "))
precision <- as.double(readline(prompt = "Enter precision: "))

if ((f(intervalBegin) * f(intervalEnd)) > 0.0) {
  print("Function has same signs at ends of interval")
} else {
  while (abs(intervalBegin - intervalEnd) > precision) {
    middle = (intervalBegin + intervalEnd) / 2.0
    
    print(paste("X: ", middle))
    
    if ((f(intervalBegin) * f(middle)) < 0.0) {
      intervalEnd = middle
    } else {
      intervalBegin = middle
    }
  }
}