#!/bin/bash

OPERADORES_DISPONIBLES=("+" "x" "-" "/")
VALID=false
FINAL_SEQUENCE=""
RE='^[0-9]+$'
NG='^-[0-9]+$'

for arg in $@; do
  valid_num=false
  valid_oper=false

  for oper in "${OPERADORES_DISPONIBLES[@]}"; do
    if [[ "$oper" == "$arg" ]] ; then
      valid_oper=true
    fi
  done

  if [[ $arg =~ $RE || $arg =~ $NG ]] ; then
    valid_num=true
  fi

  if [[ "$valid_num" != true && "$valid_oper" != true ]] ; then
    echo "INVALID CHARACTER DETECTED: $arg"
    exit
  fi

  if [[ $arg == "x" ]]; then
    FINAL_SEQUENCE+="* "
  else
    FINAL_SEQUENCE+="$arg "
  fi
done
#echo "$FINAL_SEQUENCE"
echo "$FINAL_SEQUENCE = $(($FINAL_SEQUENCE))"