added `P` command as a reverse form of `W`

* All the movement commands have shortcuts for their negative forms:
  `R` instead of `-C`, `B` instead of `-L`.
  Therefore there was always the need for a `-W` shortcut as well.
* `P` is a good choice because it is a file IO command in TECO-11,
  that does not make sense supporting.
  In Video TECO it toggles between display windows (ie. split screens)
  and I do not plan to support multiple windows in SciTECO.
* Added to the cheat sheet.

3 files changed, 38 insertions, 4 deletions

diff --git a/src/core-commands.c b/src/core-commands.c
index f39f6f9..4abf38b 100644
--- a/src/core-commands.c
+++ b/src/core-commands.c
@@ -659,7 +659,8 @@ teco_state_start_input(teco_machine_main_t *ctx, gunichar chr, GError **error)
 		['R']  = {&teco_state_start, teco_state_start_reverse},
 		['L']  = {&teco_state_start, teco_state_start_line},
 		['B']  = {&teco_state_start, teco_state_start_back},
-		['W']  = {&teco_state_start, teco_state_start_word},
+		['W']  = {&teco_state_start, teco_state_start_words},
+		['P']  = {&teco_state_start, teco_state_start_words_back},
 		['V']  = {&teco_state_start, teco_state_start_delete_words},
 		['Y']  = {&teco_state_start, teco_state_start_delete_words_back},
 		['=']  = {&teco_state_start, teco_state_start_print},
diff --git a/src/move-commands.c b/src/move-commands.c
index 8abd8ca..5339f24 100644
--- a/src/move-commands.c
+++ b/src/move-commands.c
@@ -316,7 +316,7 @@ teco_find_words(gsize *pos, teco_int_t n)
 }
 
 /*$ W word
- * [n]W -- Move dot by words
+ * [n]W -- Move dot <n> words forwards
  * -W
  * [n]:W -> Success|Failure
  *
@@ -337,7 +337,7 @@ teco_find_words(gsize *pos, teco_int_t n)
  * If colon-modified it instead returns a condition code.
  */
 void
-teco_state_start_word(teco_machine_main_t *ctx, GError **error)
+teco_state_start_words(teco_machine_main_t *ctx, GError **error)
 {
 	teco_int_t v;
 	if (!teco_expressions_pop_num_calc(&v, teco_num_sign, error))
@@ -360,6 +360,38 @@ teco_state_start_word(teco_machine_main_t *ctx, GError **error)
 		teco_expressions_push(TECO_SUCCESS);
 }
 
+/*$ P
+ * [n]P -- Move dot <n> words backwards
+ * -P
+ * [n]:P -> Success|Failure
+ *
+ * Move dot to the beginning of preceding words.
+ * It is equivalent to \(lq-nW\(rq.
+ */
+void
+teco_state_start_words_back(teco_machine_main_t *ctx, GError **error)
+{
+	teco_int_t v;
+	if (!teco_expressions_pop_num_calc(&v, teco_num_sign, error))
+		return;
+	sptr_t pos = teco_interface_ssm(SCI_GETCURRENTPOS, 0, 0);
+
+	gsize word_pos = pos;
+	if (!teco_find_words(&word_pos, -v)) {
+		if (!teco_machine_main_eval_colon(ctx))
+			teco_error_move_set(error, "P");
+		else
+			teco_expressions_push(TECO_FAILURE);
+		return;
+	}
+
+	if (teco_current_doc_must_undo())
+		undo__teco_interface_ssm(SCI_GOTOPOS, pos, 0);
+	teco_interface_ssm(SCI_GOTOPOS, word_pos, 0);
+	if (teco_machine_main_eval_colon(ctx) > 0)
+		teco_expressions_push(TECO_SUCCESS);
+}
+
 static gboolean
 teco_delete_words(teco_int_t n)
 {
diff --git a/src/move-commands.h b/src/move-commands.h
index 36acec8..9dddc8d 100644
--- a/src/move-commands.h
+++ b/src/move-commands.h
@@ -28,7 +28,8 @@ void teco_state_start_reverse(teco_machine_main_t *ctx, GError **error);
 void teco_state_start_line(teco_machine_main_t *ctx, GError **error);
 void teco_state_start_back(teco_machine_main_t *ctx, GError **error);
 
-void teco_state_start_word(teco_machine_main_t *ctx, GError **error);
+void teco_state_start_words(teco_machine_main_t *ctx, GError **error);
+void teco_state_start_words_back(teco_machine_main_t *ctx, GError **error);
 
 void teco_state_start_delete_words(teco_machine_main_t *ctx, GError **error);
 void teco_state_start_delete_words_back(teco_machine_main_t *ctx, GError **error);