159 lines
4.1 KiB
TeX
Executable File
159 lines
4.1 KiB
TeX
Executable File
\section{Turing}
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\definition{}
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An \textit{esoteric programming langauge} is a programming langauge made for fun. \par
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We'll work with two such languages today: \textit{Turing} and \textit{Befunge}.
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\definition{}
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\textit{Turing} is one of the most famous esoteric langauges, and is extremely minimalist. \par
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It consists only of eight symbols, a data pointer, and an instruction pointer.
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Turing's eight symbols are as follows:
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\begin{itemize}[itemsep=2mm]
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\item \texttt{>} : move the instruction pointer right
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\item \texttt{<} : move the instruction pointer left
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\item \texttt{+} : increment the current memory cell
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\item \texttt{-} : decrement the current memory cell
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\item \texttt{.} : output the value of the current cell as a character
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\item \texttt{,} : consume one character from input and store it at the current cell
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\item \texttt{[} : Jump to the matching \texttt{]} if the current cell is zero. \par
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otherwise, execute the next instruction.
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\item \texttt{]} : Jump back to the matching \texttt{[} if the current cell is not zero. \par
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otherwise, execute the next instruction.
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\item All other characters are ignored.
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\end{itemize}
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\problem{}
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Go to \href{https://langs.betalupi.com/}{\texttt{langs.betalupi.com}} and open the Turing editor. \par
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Clear the pre-set program in the left side of the screen and replace it with the following:
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\begin{center}
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\texttt{>+>++>+++>++++>+++++[[-]<]}
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\end{center}
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\begin{itemize}
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\item What does this program do?
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\item What does the snippet \texttt{[-]} do?
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\item Why is the first cell left as \texttt{0}?
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\end{itemize}
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\vfill
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\pagebreak
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\remark{}
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Run the program \texttt{+[+]}. Notice that the cell's value \textit{wraps}
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from \texttt{127} to \texttt{-128}! \par
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\vspace{2mm}
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Note that \texttt{[+]} has the same effect as \texttt{[-]}.
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\vfill
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\problem{}
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Write a program that moves the value of the current cell three cells to the right.
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\problem{}
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Write a program that \textbf{copies} the value of the current cell into the next cell.
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\begin{solution}
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Use a third \say{scratch} cell.
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\end{solution}
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\problem{}<bfadd>
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Write a program that adds the value of the first cell and the second cell,
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leaving the result in the second cell.
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\problem{}
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Solve \ref{bfadd} again, but multiply the two cells instead of adding.
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\problem{}
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Write a program that computes the square of the current cell.
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\vfill
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\pagebreak
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\definition{}
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Turing uses ASCII to map numbers to characters. \par
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You may use
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\href{https://www.cs.cmu.edu/~pattis/15-1XX/common/handouts/ascii.html}{\texttt{cs.cmu.edu/~pattis/15-1XX/common/handouts/ascii.html}}
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for reference.
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\vspace{5mm}
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\problem{}
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Write a program that prints the letter \texttt{a}.
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\problem{}
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Write a program that prints the alphabet as shown below: \par
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\begin{center}
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\texttt{abcdefghijklmnopqrstuvwxyz}
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\end{center}
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\problem{}
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Modify your program so that it prints the alphabet with alternating case:
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\begin{center}
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\texttt{aBcDeFgHiJkLmNoPqRsTuVwXyZ}
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\end{center}
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\problem{}
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Write a program that repeats the user's input exactly as it is entered.
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\begin{solution}
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\texttt{,[.,]}
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\end{solution}
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\problem{}
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Write a program that repeats the user's input in reverse \par
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\hint{You may use as many memory cells as you need---the editor will add more as you use them.}
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\vfill
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\pagebreak
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\problem{}
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Write a program that prints \say{Hello World}
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\problem{}
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Write a program that finds the first memory cell that is non-zero.
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\problem{}
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Write a program that initializes the tape with the following sequence:
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\begin{center}
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\texttt{3 6 12 24 48 96 192 128 0}
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\end{center}
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\problem{}
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Write a program that decodes run-length encoding.
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That is, it turns input like
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\begin{center}
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\texttt{a3j4k2d5}
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\end{center}
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into the decoded output
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\begin{center}
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\texttt{aaajjjjkkddddd}
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\end{center}
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\vfill
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\problem{Bonus}
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Write a program that prints a Turing program that prints the original program's input.
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\problem{Bonus}
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Write a program that outputs all squares between 0 and 400 %10,000
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\problem{Bonus}
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Write a program that prints the Fibonacci numbers
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\begin{solution}
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\href{https://brainfuck.org/fib\_explained.b}{\texttt{https://brainfuck.org/fib\_explained.b}}
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\end{solution}
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\vfill
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\pagebreak |