Add version of replace method with limit.

Also rename parameters in original version.

SwiftShell/String.swift

@@ -12,9 +12,18 @@
 import Foundation
 
 extension String {
-	
-	public func replace (replaceOldString: String, _ withString: String) -> String {
-		return self.stringByReplacingOccurrencesOfString(replaceOldString, withString: withString)
+
+	public func replace (oldString: String, _ newString: String) -> String {
+		return self.stringByReplacingOccurrencesOfString(oldString, withString: newString)
+	}
+
+	/** Replace the first `limit` occurrences of oldString with newString. */
+	public func replace (oldString: String, _ newString: String, limit: Int) -> String {
+		let ranges = self.findAll(oldString) |> take(limit)
+		return ranges.count == 0
+			? self
+			: self.stringByReplacingOccurrencesOfString(oldString, withString: newString,
+				range: ranges.first!.startIndex ..< ranges.last!.endIndex)
 	}
 
 	public func split (sep: String) -> [String] {

SwiftShellTests/String_Tests.swift

@@ -34,4 +34,30 @@ class String_Tests: XCTestCase {
 		XCTAssertEqual(ranges("a ").count, 2)
 	}
 
+
+	func testReplaceStringwithstring () {
+		let text = "a b c aa bb cc ab bc ca"
+
+		XCTAssertEqual( text.replace("a", "x"), "x b c xx bb cc xb bc cx")
+		XCTAssertEqual( text.replace("b ", "x"), "a xc aa bxcc axbc ca")
+	}
+
+	func testReplaceOnlySomeStringsWithString () {
+		let text = "a b c aa bb cc ab bc ca"
+
+		XCTAssertEqual( text.replace("a", "x", limit: 0), "a b c aa bb cc ab bc ca")
+		XCTAssertEqual( text.replace("a", "x", limit: 2), "x b c xa bb cc ab bc ca")
+		XCTAssertEqual( text.replace("a", "x", limit: 4), "x b c xx bb cc xb bc ca")
+		XCTAssertEqual( text.replace("a", "x", limit: 5), "x b c xx bb cc xb bc cx")
+		XCTAssertEqual( text.replace("a", "x", limit: 6), "x b c xx bb cc xb bc cx")
+
+		XCTAssertEqual( text.replace("a", "[xy]", limit: 4), "[xy] b c [xy][xy] bb cc [xy]b bc ca")
+		XCTAssertEqual( text.replace("a", "[xy]", limit: 5), "[xy] b c [xy][xy] bb cc [xy]b bc c[xy]")
+		XCTAssertEqual( text.replace("a", "[xy]", limit: 6), "[xy] b c [xy][xy] bb cc [xy]b bc c[xy]")
+
+		XCTAssertEqual( text.replace("a ", "x", limit: 0), "a b c aa bb cc ab bc ca")
+		XCTAssertEqual( text.replace("a ", "x", limit: 1), "xb c aa bb cc ab bc ca")
+		XCTAssertEqual( text.replace("a ", "x", limit: 2), "xb c axbb cc ab bc ca")
+		XCTAssertEqual( text.replace("a ", "x", limit: 3), "xb c axbb cc ab bc ca")
+	}
 }