com.livecode.char: Add in-place string reverse statement

peter-b · peter-b · commit afc8f426a9d1 · 2017-03-31T11:10:15.000+01:00
Add a new function to reverse an LCB string in-place using the
`reverse tString` statement.
diff --git a/libscript/src/char.lcb b/libscript/src/char.lcb
@@ -559,6 +559,32 @@ begin
     MCCharRepeatForEachChar(iterator, Iterand, container)
 end syntax
 
+--
+
+public foreign handler MCStringExecReverseCharsOf(inout Target as String) \
+		returns nothing binds to "<builtin>"
+
+/**
+Summary:	Reverse a string
+Target:	A string
+
+Example:
+	variable tString
+	put "abcdef" into tString
+	reverse tString
+	expect that tString is "fedcba"
+
+Description:
+Reverses the order of characters in the <Target>.
+
+Tags: Strings
+*/
+syntax ReverseCharsOf is statement
+	"reverse" <Target: Expression>
+begin
+	MCStringExecReverseCharsOf(Target)
+end syntax
+
 ----------------------------------------------------------------
 
 /**
diff --git a/libscript/src/module-char.cpp b/libscript/src/module-char.cpp
@@ -272,6 +272,15 @@ extern "C" MC_DLLEXPORT_DEF bool MCCharRepeatForEachChar(void*& x_iterator, MCSt
     return true;
 }
 
+extern "C" MC_DLLEXPORT_DEF void
+MCStringExecReverseCharsOf(MCStringRef &x_string)
+{
+    MCStringRef t_reversed = nullptr;
+    if (!MCStringCopyReversed(x_string, t_reversed))
+        return;
+    MCValueAssign(x_string, t_reversed);
+}
+
 ////////////////////////////////////////////////////////////////
 
 extern "C" MC_DLLEXPORT_DEF void MCStringEvalCodeOfChar(MCStringRef p_string, uinteger_t& r_code)
diff --git a/tests/lcb/stdlib/char.lcb b/tests/lcb/stdlib/char.lcb
@@ -406,6 +406,37 @@ public handler TestRepeatChar()
 	test "repeatchar (count)" when tCount is 3
 end handler
 
+handler TestReverse_Inplace(in pDesc as String, \
+		in pForward as String, in pReverse as String)
+
+	variable tReversed
+	put pForward into tReversed
+
+	reverse tReversed
+	test diagnostic tReversed
+	test "reverse in-place (" & pDesc & ")" when tReversed is pReverse
+
+	reverse tReversed
+	test diagnostic tReversed
+	test "rereverse in-place (" & pDesc & ")" when tReversed is pForward
+end handler
+
+public handler TestReverse()
+	TestReverse_Inplace("empty", "", "")
+	TestReverse_Inplace("native, odd", "abc", "cba")
+	TestReverse_Inplace("native, even", "abcd", "dcba")
+	TestReverse_Inplace("trivial, odd", \
+			"\u{039a}\u{03b1}\u{03bb}\u{03b7}\u{03bc}\u{03ad}\u{03c1}\u{03b1}!", \
+			"!\u{03b1}\u{03c1}\u{03ad}\u{03bc}\u{03b7}\u{03bb}\u{03b1}\u{039a}")
+	TestReverse_Inplace("trivial, even", \
+			"\u{039a}\u{03b1}\u{03bb}\u{03b7}\u{03bc}\u{03ad}\u{03c1}\u{03b1}", \
+			"\u{03b1}\u{03c1}\u{03ad}\u{03bc}\u{03b7}\u{03bb}\u{03b1}\u{039a}")
+	TestReverse_Inplace("BMP variation selector, 1", "a\u{fe0e}", "a\u{fe0e}")
+	TestReverse_Inplace("BMP variation selector, even", \
+			"\u{2b55}\u{fe0f}\u{25ef}", "\u{25ef}\u{2b55}\u{fe0f}")
+	TestReverse_Inplace("SMP, odd", "a\u{1d11e}c", "c\u{1d11e}a")
+end handler
+
 ----------------------------------------------------------------
 
 handler TestCharWithCode_Negative()
