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Repository for the Check esoteric programming language.

Using the interpreter

Run the interpreter as:

path/to/python3 path/to/src/ path/to/code.chk [initial stack values]

The Language

Check is a combination of a 1-D and 2-D language. Stack manipulation is done in 1-D, but control flow is done in 2-D.

Check operates on a stack. There are two data types that can be manipulated:

  • Unsigned Integer
  • Array

With two-dimensional semantics, control can be going in any of four directions: up, right, down, and left. The instructions ^>v< redirect the instruction pointer in their respective directions, and # switches back to one-dimensional mode.

With one-dimensional semantics, control always proceeds forwards. When it reaches the end of the line, it proceeds to the next. It has the following instructions:

  • > pushes 0 to the stack.
  • 0-9 multiply the number on the stack by 10 and then add the value of their respective digits.
  • + adds two numbers or concatenates two arrays.
  • - subtracts two numbers.
  • _ negates a number or reverses an array.
  • * multiplies two numbers or repeats an array a certain number of times.
  • $ divides a number by 2.
  • % preforms modulo on two numbers.
  • o On an integer, it outputs its character code. On an array, it flattens it and outputs it as a list of character codes. Output is without a trailing newline.
  • ) increments an integer.
  • ( decrements an integer.
  • p prints an integer or array, the way Python 3 would. Output is without a trailing newline. It does not pop the value on the stack.
  • < outputs a newline (equivalent to >10o).
  • ! preforms boolean NOT. If the integer is 0 or the array is empty, it pushes 1. Otherwise, it pushes 0.
  • [ pushes an empty array.
  • ] wraps an element in an array.
  • # switches to 2-D mode, initially pointing to the left.
  • ? switches to 2-D mode if the top stack value is 0. It does not delete the stack value.
  • " starts a string literal. The code points of each character in the string literal are collected in an array. \ is used as an escape character.
  • : duplicates the top stack element.
  • \ swaps the top two stack elements.
  • @ rotates the top three stack elements.
  • ; pops n and rotates the top n stack items. \ and @ can be seen as special cases with >2; and >3; respectively.
  • ' is like ;, but it rotates in the other direction.
  • d deletes the top stack item.
  • . makes the entire stack into an array.
  • & unpacks all array values onto the stack.
  • , gets a range [0,n) on an integer and gets the length of an array.
  • = gets the element of an array at an integer index.
  • r pops a value and stores it in the register.
  • R pushes the value from the register onto the stack.
  • ` prints everything in the stack for debugging.

Attempting to execute an invalid instruction in either mode will error. If the interpreter ever prints a stack trace, there was a bug.

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