From 550696d492c7389927d3f335bed11aa4decbcae6 Mon Sep 17 00:00:00 2001
From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Fri, 16 Jun 2023 20:47:43 +0200
Subject: shell/math: tweka comments
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
---
shell/math.c | 24 ++++++++----------------
1 file 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);
}
--
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