Add Text:reversed()

docs/text.md

@@ -1125,6 +1125,31 @@ replacement text.
 
 ---
 
+## `reversed`
+
+**Description:**  
+Return a text that has the grapheme clusters in reverse order.
+
+**Signature:**  
+```tomo
+func reversed(text: Text -> Text)
+```
+
+**Parameters:**
+
+- `text`: The text to reverse.
+
+**Returns:**  
+A reversed version of the text.
+
+**Example:**  
+```tomo
+>> "Abc":reversed()
+= "cbA"
+```
+
+---
+
 ## `slice`
 
 **Description:**  

environment.c

@@ -415,6 +415,7 @@ env_t *new_compilation_unit(CORD libname)
             {"repeat", "Text$repeat", "func(text:Text, count:Int -> Text)"},
             {"replace", "Text$replace", "func(text:Text, pattern:Pattern, replacement:Text, backref=$/\\/, recursive=yes -> Text)"},
             {"replace_all", "Text$replace_all", "func(text:Text, replacements:{Pattern:Text}, backref=$/\\/, recursive=yes -> Text)"},
+            {"reversed", "Text$reversed", "func(text:Text -> Text)"},
             {"slice", "Text$slice", "func(text:Text, from=1, to=-1 -> Text)"},
             {"split", "Text$split", "func(text:Text, pattern=$Pattern'' -> [Text])"},
             {"starts_with", "Text$starts_with", "func(text,prefix:Text -> Bool)"},

stdlib/text.c

@@ -572,6 +572,47 @@ public Text_t Text$to(Text_t text, Int_t last)
     return Text$slice(text, I_small(1), last);
 }
 
+public Text_t Text$reversed(Text_t text)
+{
+    switch (text.tag) {
+    case TEXT_SHORT_ASCII: {
+        Text_t ret = text;
+        for (int64_t i = 0; i < text.length; i++)
+            ret.short_ascii[text.length-1-i] = text.short_ascii[i];
+        return ret;
+    }
+    case TEXT_ASCII: {
+        Text_t ret = text;
+        ret.ascii = GC_MALLOC_ATOMIC(sizeof(uint8_t[text.length]));
+        for (int64_t i = 0; i < text.length; i++)
+            ((char*)ret.ascii)[text.length-1-i] = text.ascii[i];
+        return ret;
+    }
+    case TEXT_SHORT_GRAPHEMES: {
+        Text_t ret = text;
+        for (int64_t i = 0; i < text.length; i++)
+            ret.short_graphemes[text.length-1-i] = text.short_graphemes[i];
+        return ret;
+    }
+    case TEXT_GRAPHEMES: {
+        Text_t ret = text;
+        ret.graphemes = GC_MALLOC_ATOMIC(sizeof(int32_t[text.length]));
+        for (int64_t i = 0; i < text.length; i++)
+            ((int32_t*)ret.graphemes)[text.length-1-i] = text.graphemes[i];
+        return ret;
+    }
+    case TEXT_SUBTEXT: {
+        Text_t ret = text;
+        int64_t n = num_subtexts(text);
+        ret.subtexts = GC_MALLOC(sizeof(Text_t*[n]));
+        for (int64_t i = 0; i < n; i++)
+            ret.subtexts[n-1-i] = Text$reversed(text.subtexts[i]);
+        return ret;
+    }
+    default: errx(1, "Invalid tag");
+    }
+}
+
 public Text_t Text$cluster(Text_t text, Int_t index_int)
 {
     int64_t index = Int_to_Int64(index_int, false);

stdlib/text.h

@@ -31,6 +31,7 @@ Text_t Text$_concat(int n, Text_t items[n]);
 Text_t Text$slice(Text_t text, Int_t first_int, Int_t last_int);
 Text_t Text$from(Text_t text, Int_t first);
 Text_t Text$to(Text_t text, Int_t last);
+Text_t Text$reversed(Text_t text);
 Text_t Text$cluster(Text_t text, Int_t index_int);
 OptionalText_t Text$from_str(const char *str);
 OptionalText_t Text$from_strn(const char *str, size_t len);

test/text.tm

@@ -292,6 +292,9 @@ func main():
 	>> "abcde":starts_with("cd")
 	= no
 
+	>> ("hello" ++ " " ++ "Amélie"):reversed()
+	= "eilémA olleh" : Text
+
 	do:
 		!! Testing concatenation-stability:
 		>> ab := Text.from_codepoint_names(["LATIN SMALL LETTER E", "COMBINING VERTICAL LINE BELOW"])!