shell: fix arithmentic evaluation of "++7" and such (it is + + 7, i.e. 7)

function                                             old     new   delta
evaluate_string                                      945     988     +43

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/ash_test/ash-arith/arith.right

@@ -97,6 +97,7 @@ ghi
 3 3
 4 4
 4 4
+7 7
 ./arith.tests: line 257: arithmetic syntax error
 ./arith.tests: line 259: arithmetic syntax error
 ./arith.tests: line 260: arithmetic syntax error
@@ -105,6 +106,8 @@ ghi
 4 4
 7 7
 -7 -7
+7
+7
 ./arith1.sub: line 2: arithmetic syntax error
 ./arith1.sub: line 3: arithmetic syntax error
 ./arith1.sub: line 4: arithmetic syntax error
@@ -119,11 +122,12 @@ ghi
 2 2
 -2 -2
 1 1
-./arith1.sub: line 37: arithmetic syntax error
-./arith2.sub: line 2: arithmetic syntax error
-./arith2.sub: line 3: arithmetic syntax error
-./arith2.sub: line 4: arithmetic syntax error
-./arith2.sub: line 5: arithmetic syntax error
+7
+7
+7
+7
+7
+7
 5 5
 1 1
 6 6
@@ -132,8 +136,10 @@ ghi
 1 1
 4 4
 0 0
-./arith2.sub: line 42: arithmetic syntax error
-./arith2.sub: line 47: arithmetic syntax error
+-7
+-7
+7
+7
 8 12
 ./arith.tests: line 290: arithmetic syntax error
 42

shell/ash_test/ash-arith/arith.tests

@@ -252,8 +252,8 @@ echo 3 $x
 echo 4 $(( ++x ))
 echo 4 $x
 
-# bash 3.2 apparently thinks that ++7 is 7
-#ash# echo 7 $(( ++7 ))
+# ++ is not a inc operator on non-variable, it is the + + sequence
+echo 7 $(( ++7 ))
 (  echo $(( 7-- ))    )
 
 (  echo $(( --x=7 ))  )
@@ -267,9 +267,9 @@ echo 4 $x
 echo 7 $(( +7 ))
 echo -7 $(( -7 ))
 
-# bash 3.2 apparently thinks that ++7 is 7
-#ash# echo $(( ++7 ))
-#ash# echo $(( --7 ))
+# ++ is not a inc operator on non-variable, it is the + + sequence
+echo $(( ++7 ))
+echo $(( --7 ))
 
 ${THIS_SH} ./arith1.sub
 ${THIS_SH} ./arith2.sub

shell/ash_test/ash-arith/arith1.sub

@@ -35,6 +35,6 @@ echo 1 $a
 
 #ash# (( ++ ))
 (  echo $(( +++7 ))  )
-# bash 3.2 apparently thinks that ++ +7 is 7
-#ash# echo $(( ++ + 7 ))
+# ++ is not a inc operator on non-variable, it is the + + sequence
+echo $(( ++ + 7 ))
 #ash# (( -- ))

shell/ash_test/ash-arith/arith2.sub

@@ -1,4 +1,4 @@
-# bash 3.2 apparently thinks that ++7 is 7 etc
+# ++ and -- are not inc/dec operators on non-variables, they are + + and - - sequences
 (  echo $(( --7 ))   )
 (  echo $(( ++7 ))   )
 (  echo $(( -- 7 ))  )
@@ -37,13 +37,13 @@ echo 4 $(( 4 - -- a ))
 echo 0 $a
 
 #ash# (( -- ))
-# bash 3.2 apparently thinks that ---7 is -7
-#ash# echo $(( ---7 ))
+# -- is not a dec operator on non-variable, it is the - - sequence
+echo $(( ---7 ))
 (  echo $(( -- - 7 ))  )
 
 #ash# (( ++ ))
-# bash 3.2: 7
-#ash# echo 7 $(( ++7 ))
+# ++ is not a inc operator on non-variable, it is the + + sequence
+echo $(( ++7 ))
 (  echo $(( ++ + 7 ))  )
 
 # bash 3.2: -7