Extract Mantissa and Exponent of the Floating-Point Value

frexp.R

#!/usr/bin/Rscript --vanilla
#
# Author: LogIN- <info{@/at}ivantomic{.}com
# License: MIT
# 
# Description:
# 
# Extract Mantissa and Exponent of the Floating-Point Value
# frexp() returns an list containing Mantissa and Exponent of the Floating-Point Value
# 
# Parameters:
# arg
# number
# 
# Example:
# frexp(1.5)
# => [0.75, 1]

frexp <- function(input){

  input <- as.numeric(input)
  result <- c(0, 0)

  if (input != 0 && is.finite(input)) {
        absInp <- abs(input)
        exp <- max(-1023, floor(log2(absInp)) + 1)
        x <- absInp * 2^ -exp
        while (x < 0.5) {
            x <- x * 2
            exp <- exp - 1
        }
        while (x >= 1) {
            x <- x * 0.5
            exp <- exp + 1
        }
        if (input < 0) {
            x <- -x
        }
        result <- c(x, exp)
    }
    return(result)
}