Lambda programming language

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The Lambda Programming Language is a programming language based on lambda calculus and a simplistic von Neumann architecture with a linear memory space. The registers are also memory-mapped and allows for self-modifying code. It provides a small number of instructions

Lambda provides only one type (the integer), which also means that there is no way to actually write a "Hello, world" program (the compiler and the interpreter do not deal with ASCII characters).

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The Lambda language

Lambda has a simple syntax with only four basic rules:

  • All instructions are separated by newlines; tokens are separated by spaces.
  • A ";" character at the end of an operator means that the operator is a GOTO label. The jump can be made by simply calling that operator
  • An instruction with an operator ending with a "!" character returns the address of the operator.
  • Comments can be written after "//" characters

Six basic instructions are provided (the number in parenthesis is the numerical opcode value of the instruction):

  • NOP (0): No operation, updates instruction pointer to next operation.
  • READ (1): Read a value from memory; it interprets the result of the next expression as a memory address, returning the value stored at it.
  • LOAD (2): Loads a value to memory; the expression immediately following is evaluated as the address, and the expression after it is evaluated to the value to be stored.
  • ADD (3): Adds a value to that of a memory address; the expression immediately following is evaluated as the memory address, and the one after it as the value to be added.
  • PRINT (4): Prints the value returned by evaluating the expression following immediately.

There are three memory-mapped registers:

  • The Instruction register, holding the address of the current instruction pointer. It is mapped at the address 32.
  • The Data register, holding the address of the next expression's start on jumps, enabling the machine to perform jumps. It is mapped at the address 34.
  • The Result register, holding the value of the current result while evaluating an expression. It is mapped at the address 36.
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Examples

The following program prints the number 999 and demonstrates the usage of jumps: 

print999
back:
exit
print999:
print 999
back
exit:
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