Một ngôn ngữ lập trình nhất định được gọi là Turing-Complete nếu có thể chỉ ra rằng nó tương đương với máy tính Turing.
TSQL là Turing Complete vì chúng tôi có thể tạo trình thông dịch BrainFuck trong TSQL.
Trình thông dịch BrainFuck bằng SQL - GitHub
Mã được cung cấp hoạt động trong bộ nhớ và không sửa đổi cơ sở dữ liệu.
-- Brain Fuck interpreter in SQL
DECLARE @Code VARCHAR(MAX) = ', [>,] < [.<]'
DECLARE @Input VARCHAR(MAX) = '!dlroW olleH';
-- Creates a "BrainFuck" DataBase.
-- CREATE DATABASE BrainFuck;
-- Creates the Source code table
DECLARE @CodeTable TABLE (
[Id] INT IDENTITY(1,1) PRIMARY KEY NOT NULL,
[Command] CHAR(1) NOT NULL
);
-- Populate the source code into CodeTable
DECLARE @CodeLen INT = LEN(@Code);
DECLARE @CodePos INT = 0;
DECLARE @CodeChar CHAR(1);
WHILE @CodePos < @CodeLen
BEGIN
SET @CodePos = @CodePos + 1;
SET @CodeChar = SUBSTRING(@Code, @CodePos, 1);
IF @CodeChar IN ('+', '-', '>', '<', ',', '.', '[', ']')
INSERT INTO @CodeTable ([Command]) VALUES (@CodeChar)
END
-- Creates the Input table
DECLARE @InputTable TABLE (
[Id] INT IDENTITY(1,1) PRIMARY KEY NOT NULL,
[Char] CHAR(1) NOT NULL
);
-- Populate the input text into InputTable
DECLARE @InputLen INT = LEN(@Input);
DECLARE @InputPos INT = 0;
WHILE @InputPos < @InputLen
BEGIN
SET @InputPos = @InputPos + 1;
INSERT INTO @InputTable ([Char])
VALUES (SUBSTRING(@Input, @InputPos, 1))
END
-- Creates the Output table
DECLARE @OutputTable TABLE (
[Id] INT IDENTITY(1,1) PRIMARY KEY NOT NULL,
[Char] CHAR(1) NOT NULL
);
-- Creates the Buffer table
DECLARE @BufferTable TABLE (
[Id] INT IDENTITY(1,1) PRIMARY KEY NOT NULL,
[Memory] INT DEFAULT 0 NOT NULL
);
INSERT INTO @BufferTable ([Memory])
VALUES (0);
-- Initialization of temporary variables
DECLARE @CodeLength INT = (SELECT COUNT(*) FROM @CodeTable);
DECLARE @CodeIndex INT = 0;
DECLARE @Pointer INT = 1;
DECLARE @InputIndex INT = 0;
DECLARE @Command CHAR(1);
DECLARE @Depth INT;
-- Main calculation cycle
WHILE @CodeIndex < @CodeLength
BEGIN
-- Read the next command.
SET @CodeIndex = @CodeIndex + 1;
SET @Command = (SELECT [Command] FROM @CodeTable WHERE [Id] = @CodeIndex);
-- Increment the pointer.
IF @Command = '>'
BEGIN
SET @Pointer = @Pointer + 1;
IF (SELECT [Id] FROM @BufferTable WHERE [Id] = @Pointer) IS NULL
INSERT INTO @BufferTable ([Memory]) VALUES (0);
END
-- Decrement the pointer.
ELSE IF @Command = '<'
SET @Pointer = @Pointer - 1;
-- Increment the byte at the pointer.
ELSE IF @Command = '+'
UPDATE @BufferTable SET [Memory] = [Memory] + 1 WHERE [Id] = @Pointer;
-- Decrement the byte at the pointer.
ELSE IF @Command = '-'
UPDATE @BufferTable SET [Memory] = [Memory] - 1 WHERE [Id] = @Pointer;
-- Output the byte at the pointer.
ELSE IF @Command = '.'
INSERT INTO @OutputTable ([Char]) (SELECT CHAR([Memory]) FROM @BufferTable WHERE [Id] = @Pointer);
-- Input a byte and store it in the byte at the pointer.
ELSE IF @Command = ','
BEGIN
SET @InputIndex = @InputIndex + 1;
UPDATE @BufferTable SET [Memory] = COALESCE((SELECT ASCII([Char]) FROM @InputTable WHERE [Id] = @InputIndex), 0) WHERE [Id] = @Pointer;
END
-- Jump forward past the matching ] if the byte at the pointer is zero.
ELSE IF @Command = '[' AND COALESCE((SELECT [Memory] FROM @BufferTable WHERE [Id] = @Pointer), 0) = 0
BEGIN
SET @Depth = 1;
WHILE @Depth > 0
BEGIN
SET @CodeIndex = @CodeIndex + 1;
SET @Command = (SELECT [Command] FROM @CodeTable WHERE [Id] = @CodeIndex);
IF @Command = '[' SET @Depth = @Depth + 1;
ELSE IF @Command = ']' SET @Depth = @Depth - 1;
END
END
-- Jump backwards to the matching [ unless the byte at the pointer is zero.
ELSE IF @Command = ']' AND COALESCE((SELECT [Memory] FROM @BufferTable WHERE [Id] = @Pointer), 0) != 0
BEGIN
SET @Depth = 1;
WHILE @Depth > 0
BEGIN
SET @CodeIndex = @CodeIndex - 1;
SET @Command = (SELECT [Command] FROM @CodeTable WHERE [Id] = @CodeIndex);
IF @Command = ']' SET @Depth = @Depth + 1;
ELSE IF @Command = '[' SET @Depth = @Depth - 1;
END
END
END;
-- Collects and prints the output
DECLARE @Output VARCHAR(MAX);
SELECT @Output = COALESCE(@Output, '') + [Char]
FROM @OutputTable;
PRINT @Output;
Go