properly document some functions in expressions.c and simplified code

* Practically all calls to teco_expressions_args() must be preceded by teco_expressions_eval().
* In code paths where we know that teco_expressions_args() > 0, it is safe
  to call teco_expressions_pop_num(0) instead of teco_expressions_pop_num_calc().
  This is both easier and faster.
* teco_expressions_pop_num_calc() is for simple applications where you just want to get
  a command argument with default (implied) values.
  Since it includes teco_expressions_eval(), we can avoid superfluous calls.
* -EC...$ turned out to be broken and is fixed now.
  A test case has been added.

1 files changed, 2 insertions, 6 deletions

diff --git a/src/ring.c b/src/ring.c
index 72aab93..d389e52 100644
--- a/src/ring.c
+++ b/src/ring.c
@@ -556,9 +556,7 @@ teco_state_save_file_done(teco_machine_main_t *ctx, const teco_string_t *str, GE
 	 */
 	teco_buffer_t *buffer = teco_ring_current;
 	if (teco_expressions_args() > 0) {
-		teco_int_t id;
-		if (!teco_expressions_pop_num_calc(&id, 0, error))
-			return NULL;
+		teco_int_t id = teco_expressions_pop_num(0);
 		buffer = teco_ring_find(id);
 		if (!buffer) {
 			teco_error_invalidbuf_set(error, id);
@@ -691,9 +689,7 @@ teco_state_ecommand_close(teco_machine_main_t *ctx, GError **error)
 	teco_buffer_t *buffer;
 	gboolean force;
 	if (teco_expressions_args() > 0) {
-		teco_int_t id;
-		if (!teco_expressions_pop_num_calc(&id, 0, error))
-			return;
+		teco_int_t id = teco_expressions_pop_num(0);
 		buffer = teco_ring_find(ABS(id));
 		if (!buffer) {
 			teco_error_invalidbuf_set(error, ABS(id));