# test expression evaluation with unset variables
set -u

( echo $(( a > 4 )) ; echo after 1 )	# error
( echo $(( a[0] > 4 )); echo after 2)	# error

set +u
( echo $(( a > 4 )) ; echo after 3 $? )
( echo $(( a[0] > 4 )); echo after 4 $?)

# this is a recursion stack error
a=b
b=a
echo $(( a + 7 ))

# make sure command printing works for arithmetic expansions and commands
set -x
var=42

echo $(( $var ))
echo $?

echo $(( $null ))
echo $?

(( $var ))
echo $?

(( $null ))
echo $?

set +x

# invalid expressions in different cases
x=4+
declare -i x
x+=7 y=4
echo x = $x y = $y