First commit

exercises/ch04/ex4_1.lua

@@ -0,0 +1,12 @@
+local str1 = "<![CDATA[\n  Hello World\n]]>"
+
+print(str1)
+
+print("\n------------------------------\n")
+
+local str2 = [=[
+<![CDATA[
+  Hello World
+]]>]=]
+
+print(str2)

exercises/ch04/ex4_3.lua

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+local function insert(str, i, o)
+    local first_half = str:sub(1, i - 1)
+    local latter_half = str:sub(i, -1)
+    return first_half .. o .. latter_half
+end
+
+local function tests()
+    local res = insert("hello world", 1, "start: ")
+    print(('insert("hello world", 1, "start: ") --> %s'):format(res))
+
+    res = insert("hello world", 7, "small ")
+    print(('insert("hello world", 7, "small ")  --> %s'):format(res))
+
+    res = insert("hello world", 12, "!")
+    print(('insert("hello world", 12, "!")      --> %s'):format(res))
+end
+
+tests()

exercises/ch04/ex4_4.lua

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+local function insert(str, i, o)
+    i = utf8.offset(str, i)
+    local first_half = str:sub(1, i - 1)
+    local latter_half = str:sub(i, -1)
+    return first_half .. o .. latter_half
+end
+
+local function tests()
+    local res = insert("ação", 5, "!")
+    print(('insert("ação", 5, "!") --> %s'):format(res))
+end
+
+tests()

exercises/ch04/ex4_5.lua

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+local function remove(str, start, length)
+    local start_part = str:sub(1, start - 1)
+    local end_part = str:sub(start + length, -1)
+    return start_part .. end_part
+end
+
+print(remove("hello world", 7, 4))

exercises/ch04/ex4_6.lua

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+local function remove(str, start, length)
+    local slice_start = utf8.offset(str, start - 1)
+    local slice_end = utf8.offset(str, start + length)
+    local start_part = str:sub(1, slice_start)
+    local end_part = str:sub(slice_end)
+    return start_part .. end_part
+end
+
+print(remove("ação", 2, 2))

exercises/ch04/ex4_7.lua

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+local function ispali(str)
+    str = str:lower()
+    return str == str:reverse()
+end
+
+print(ispali("step on no pets"))
+print(ispali("banana"))

exercises/ch04/ex4_8.lua

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+local function remove(str, start, _end)
+    local start_part = str:sub(1, start - 1)
+    local end_part = str:sub(_end + 1, -1)
+    return start_part .. end_part
+end
+
+local function remove_patterns(str, pattern)
+    while true do
+        local rem_start, rem_end, _ = str:find(pattern)
+        if rem_start == nil then
+            break
+        end
+        str = remove(str, rem_start, rem_end)
+    end
+
+    return str
+end
+
+local function ispali(str)
+    str = str:lower()
+
+    -- format
+    str = remove_patterns(str, "%s")
+    str = remove_patterns(str, "%p")
+
+    return str == str:reverse()
+end
+
+local function test(str)
+    print(("%s: %q"):format(str, ispali(str)))
+end
+
+test("step on no pets")
+test("banana")
+
+print()
+
+test("Step. On no   pets!")
+test("Banana??")