finish long subtraction

subtraction/sub

@@ -0,0 +1,119 @@
+#!/bin/sh
+# long subtraction !?
+# $f1 - $f2
+countd() { # count decimal places
+  m="$1"; n=${2:-0}; while [ "$m" ]; do
+    : $((n+=1))
+    next="${m%?}"
+    [ "${m#$next}" = "." ] && {
+      break
+    } || {
+      m="$next"
+    }
+  done
+  echo "$n"
+}
+borrow(){
+  # $2 current number (to increase) 
+  # $1 as whole number; will return modified
+  # $3 as $next
+  b="${1%$2}"; b="${b#${3%?}}"
+  [ "$b" -gt 0 ] && {
+    c1="$2";
+    [ "$b" -eq 10 ] && {
+      o="${1%$b$2}"; : $((b-=1)); o="${o}0${b}$c1" # eg 21 = 2090 10
+      # tbh idk why this works; 2090 should acctually be 1 10 9 10
+      # which somehow becomes 209 10 ? I'm guessing a second borrow call is made
+      # and that somehow corrects it; but again idk; a second borrow call /is/ made
+      # but idk how it corrects it
+    } || {
+      o="${1%$b$2}"; : $((b-=1)); o="$o$b$c1"
+    }
+    : $((c1+=10))
+    echo "$o $c1"
+  } || { # otherwise use recusion
+    o="${1#${3%?}}"; o="${o%$2}"
+    borrow "$1" "$o" "${3%?}"
+  }
+}
+[ -z "${1##*.*}" -o -z "${2##*.*}" ] && {
+
+  if [ ! -z "${1##*.*}" ]; then # if $1 is not float 
+    zp1="$1"; zp2="${2%.*}${2#*.}"
+  elif [ ! -z "${2##*.*}" ]; then
+    zp1="${1%.*}${1#*.}"; zp2="$2"
+  else
+    zp1="${1%.*}${1#*.}"; zp2="${2%.*}${2#*.}"
+  fi # yank out decimal places to compare
+  if [ "${#zp1}" -gt "${#zp2}" ]; then
+    until [ "${#zp2}" -eq "${#zp1}" ]; do
+      zp2="${zp2}0"
+    done
+  elif [ "${#zp1}" -lt "${#zp2}" ]; then
+    until [ "${#zp1}" -eq "${#zp2}" ]; do
+      zp1="${zp1}0"
+    done
+  fi
+  [ "$zp2" -gt "$zp1" ] && {
+    set -- "$2" "$1"
+    nr=-
+  }
+  # above handles negative results
+  
+  # determine decimal point
+  if [ "${#1}" -gt "${#2}" -a -z "${1##*.*}" ]; then # if $1 has no decimal points it should not be counted
+  # this fixes a but when $1 is longer than $2 but has no decimal points 
+    dn=$(countd "$1")
+  elif [ "${#1}" -lt "${#2}" -a -z "${2##*.*}" ]; then # same here
+    dn=$(countd "$2")
+  else # equal
+    dn=$(countd "$2")
+  fi 
+  zp1="${1%%.*}"; zp2="${2%%.*}"
+  [ "${#zp1}" -gt "${#zp2}" ] && until [ "${#zp1}" -eq "${#zp2}" ]; do
+    set -- "$1" "0$2"
+    zp1="${1%%.*}"; zp2="${2%%.*}"
+  done
+  [ "${#zp1}" -lt "${#zp2}" ] && until [ "${#zp1}" -eq "${#zp2}" ]; do
+    set -- "0$1" "$2"
+    zp1="${1%%.*}"; zp2="${2%%.*}"
+  done; unset zp1 zp2
+  [ "$dn" -gt 0 ] && : $((dn-=1))
+  if [ ! -z "${1##*.*}" ]; then # if $1 not float
+    set -- "${1}.0" "$2"
+  elif [ ! -z "${2##*.*}" ]; then
+    set -- "$1" "${2}.0"
+  fi
+  #echo "$1 $2"
+  set -- "${1%.*}${1#*.}" "${2%.*}${2#*.}" # remove decimals
+  f1="$1"; f2="$2"
+  [ "${#f1}" -lt "${#f2}" ] && until [ "${#f1}" -eq "${#f2}" ]; do
+    f1="${f1}0"
+  done
+  [ "${#f1}" -gt "${#f2}" ] && until [ "${#f2}" -eq "${#f1}" ]; do
+    f2="${f2}0"
+  done # 0 padding
+  #echo "$f1 - $f2"
+  while [ "$f1" ]; do
+    while [ "$f2" ]; do # shift over both numbers; double while
+      next1="${f1%?}"; next2="${f2%?}"; c1="${f1#$next1}"; c2="${f2#$next2}"
+      [ "$c1" -lt "$c2" ] && { # regroup
+        b=$(borrow "$f1" "$c1" "$next1")
+        c1="${b#* }"; f1="${b% *}"; next1="${f1%?}"
+        #echo "-- $f1 / $b"
+      }
+      #echo "$c1 - $c2 | $f1 - $f2"
+      o="$((c1-c2))$o" # subtract
+      f1="$next1"; f2="$next2"
+    done
+  done
+  [ "$dn" -gt 0 ] && {
+    n=0; f1="$o"; while [ "$f1" ]; do
+      next="${f1%?}"
+      : $((n+=1))
+      [ "$n" -eq "$dn" ] && o="$next.${o#${f1%?}}"
+      f1="$next"
+    done
+  }
+  echo "${nr}$o" # $nr is for negative handling
+} || echo $(($1-$2)) # NOT float