feat(stdlib): add new functions in std/text (#373)

* feat(stdlib): add new functions in `std/text`

- `reverse`: reverses the given text.
- `is_prefix`: checks if a string is a prefix of another string.
- `is_suffix`: checks if a string is a suffix of another string.

These addition of `is_prefix` & `is_suffix` complement the existing `contains` function.

* refactor: change `is_prefix` & `is_suffix` function names

is_prefix -> starts_with
is_suffix -> ends_with

src/std/text.ab

@@ -82,3 +82,26 @@ pub fun contains(text: Text, phrase: Text): Bool {
 
   return result == "1"
 }
+
+/// Reverse a text using `rev`
+pub fun reverse(text: Text): Text {
+    return unsafe $echo "{text}" | rev$
+}
+
+/// Check if text starts with a value
+pub fun starts_with(text: Text, prefix: Text): Bool {
+  let result = unsafe $if [[ "{text}" == "{prefix}"* ]]; then
+    echo 1
+  fi$
+
+  return result == "1"
+}
+
+/// Check if text ends with a value
+pub fun ends_with(text: Text, suffix: Text): Bool {
+  let result = unsafe $if [[ "{text}" == *"{suffix}" ]]; then
+    echo 1
+  fi$
+
+  return result == "1"
+}

src/tests/stdlib/ends_with.ab

@@ -0,0 +1,7 @@
+import * from "std/text"
+
+main {
+    if ends_with("hello world", "world") {
+        echo "Succeded"
+    } 
+} 

src/tests/stdlib/reverse.ab

@@ -0,0 +1,8 @@
+import * from "std/text"
+
+// Output
+// dlrow olleh
+
+main {
+    echo reverse("hello world")
+} 

src/tests/stdlib/starts_with.ab

@@ -0,0 +1,7 @@
+import * from "std/text"
+
+main {
+    if starts_with("hello world", "hello") {
+        echo "Succeded"
+    } 
+}