conway's game of life

conway.bash

#!/usr/bin/env bash

tput civis

declare -a arr0
declare -a arr1
idx=0
declare -n cur=arr0
declare -n next=arr1

# DEAD='⬜'
# ALIVE='⬛'
DEAD=' '
ALIVE='▓'
mapfile -t arr0
height="${#cur[@]}"
width="${#cur[0]}"

for ((i=0; i<height; i++)); do
  before=${cur[i]}
  after=${before//#/$ALIVE}
  cur[i]=${after//\./$DEAD}
done


next=("${cur[@]}")


function get {
  local r=$1
  local c=$2
  c=$((c%width))
  local row="${cur[r%height]}"
  echo "${row:$c:1}"
}


render() {
  printf "\e[%s;%sH" 1 1
  printf "%s\n" "${next[@]}"
}

step() {
  local r c i j
  local self neighbor
  local line
  for ((r=0; r<height; ++r)); do
  line=""
  for ((c=0; c<width; ++c)); do
    sum=0
    for i in -1 0 1; do
    for j in -1 0 1; do
    [ $j -eq 0 ] && [ $i -eq 0 ] && continue
    neighbor=${ get $((r + i)) $((c + j)); }
    if [[ $neighbor == "$ALIVE" ]]; then
      ((sum++))
    fi
    done
    done
    self=${ get $r $c; }
    if [[ $self == "$ALIVE" ]]; then
      # we are live
      if [[ sum -lt 2 ]]; then
        line=$line$DEAD
      elif [[ sum -gt 3 ]]; then
        line=$line$DEAD
      else
        line="$line$ALIVE"
      fi
    elif [[ sum -eq 3 ]]; then
      line="$line$ALIVE"
    else
      line="$line$DEAD"
    fi
  done
  next[r]=$line
  done
  declare -gn next=arr${idx}
  ((idx=(idx+1)%2))
  declare -gn cur=arr${idx}
}

clear
while :; do
  render
  step
done