shell/math: tweka comments

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

1 files changed, 8 insertions, 16 deletions

diff --git a/shell/math.c b/shell/math.c
index b1aabef9d..2959e57ea 100644
--- a/shell/math.c
+++ b/shell/math.c
@@ -46,7 +46,6 @@
  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
-
 /* This is my infix parser/evaluator. It is optimized for size, intended
  * as a replacement for yacc-based parsers. However, it may well be faster
  * than a comparable parser written in yacc. The supported operators are
@@ -61,7 +60,6 @@
  * to the stack instead of adding them to a queue to end up with an
  * expression).
  */
-
 /*
  * Aug 24, 2001              Manuel Novoa III
  *
@@ -245,7 +243,6 @@ is_right_associative(operator prec)
         || prec == PREC(TOK_CONDITIONAL);
 }
 
-
 typedef struct {
         arith_t val;
         char *var_name;
@@ -254,13 +251,11 @@ typedef struct {
 #define VALID_NAME(name) (name)
 #define NOT_NAME(name)   (!(name))
 
-
 typedef struct remembered_name {
         struct remembered_name *next;
         const char *var_name;
 } remembered_name;
 
-
 static arith_t
 evaluate_string(arith_state_t *math_state, const char *expr);
 
@@ -278,7 +273,7 @@ arith_lookup_val(arith_state_t *math_state, var_or_num_t *t)
                          */
                         for (cur = math_state->list_of_recursed_names; cur; cur = cur->next) {
                                 if (strcmp(cur->var_name, t->var_name) == 0) {
-                                        /* Yes */
+                                        /* yes */
                                         return "expression recursion loop detected";
                                 }
                         }
@@ -500,7 +495,6 @@ static const char op_tokens[] ALIGN1 = {
         '+',        0, TOK_ADD,
         '-',        0, TOK_SUB,
         '^',        0, TOK_BXOR,
-        /* uniq */
         '~',        0, TOK_BNOT,
         ',',        0, TOK_COMMA,
         '?',        0, TOK_CONDITIONAL,
@@ -869,14 +863,9 @@ evaluate_string(arith_state_t *math_state, const char *expr)
                                 if (errmsg)
                                         goto err_with_custom_msg;
 dbg("    numstack:%d val:%lld '%s'", (int)(numstackptr - numstack), numstackptr[-1].val, numstackptr[-1].var_name);
-                                /* For ternary ?: we need to remove ? from opstack too, not just : */
                                 if (prev_op == TOK_CONDITIONAL_SEP) {
-                                        // This is caught in arith_apply()
-                                        //if (opstackptr == opstack) {
-                                        //      /* Example: $((2:3)) */
-                                        //      errmsg = "where is your ? in ?:";
-                                        //      goto err_with_custom_msg;
-                                        //}
+                                        /* We just executed ":" */
+                                        /* Remove "?" from opstack too, not just ":" */
                                         opstackptr--;
                                         if (*opstackptr != TOK_CONDITIONAL) {
                                                 /* Example: $((1,2:3)) */
@@ -890,12 +879,14 @@ dbg("    numstack:%d val:%lld '%s'", (int)(numstackptr - numstack), numstackptr[
                                         dbg("':' executed: evaluation_disabled=%llx (restored)", EVAL_DISABLED);
                                 }
                         } /* while (opstack not empty) */
+
                         if (op == TOK_RPAREN) /* unpaired RPAREN? */
                                 goto err;
  check_cond:
                         if (op == TOK_CONDITIONAL) {
-                                /* We know the value of EXPR in "EXPR ? ..."
-                                 * Should we stop evaluating now? */
+                                /* We just now evaluated EXPR before "?".
+                                 * Should we disable evaluation now?
+                                 */
                                 if (math_state->evaluation_disabled & TOP_BIT_ULL)
                                         goto err; /* >63 levels of ?: nesting not supported */
                                 math_state->evaluation_disabled <<= 1;
@@ -915,6 +906,7 @@ dbg("    numstack:%d val:%lld '%s'", (int)(numstackptr - numstack), numstackptr[
                         insert_op = 0xff;
                         dbg("inserting %02x", op);
                         if (op == TOK_CONDITIONAL_SEP) {
+                                /* The next token is ":". Toggle "do not evaluate" bit */
                                 math_state->evaluation_disabled ^= 1;
                                 dbg("':' entered: evaluation_disabled=%llx (negated)", EVAL_DISABLED);
                         }