lmc_fast

Faster Durham LMC interpreter/tester

How to use

1. Create a text file and write your code into it
2. Run main.py
3. Enter the name of the text file
4. Optionally enter the name of a text file containing tests if you want to test your program
5. Press enter to run the program
6. Can type enter to run the program again; this helps test that your program resets properly after halting (not applicable in test mode)

Test format

All tests should be in the following format:
name;input_0,input_1,input_2,input_...,input_n;output;maxCycles
A name, n inputs, a single expected output, and the maximum number of F-E the test should run for before it's assumed the program is stuck. Multiple tests can be placed in the same file as long as they are separated by a newline.

How to generate cases

Just run gentest.py. You can change the TEST_CASES to how many test cases to generate and FILENAME to change the filename to which the tests are saved to. You can add special test cases by adding an entry (a, b, c) into the specials array.

Instruction set

All instructions must be prefixed either with a whitespace or a label: an alias for the mailbox that instruction/data is stored in. You can use _mailboxNumber to reference a specific mailbox.

• ADD <label> Add value at label to value stored in calculator
• SUB <label> Subtract value at label from value stored in calculator. Will set the negative flag if the result underflows
• STO <label> Store the value in the accumulator at label
• LDA <label> Load the value at label into calculator. Resets the negative flag
• BR <label> Jump to label
• BRZ <label> Jump to label only if the value stored in the calculator is 0
• BRP <label> Jump to label only if the negative flag is not set (a value of 0 would still cause a jump, despite 0 not being positive)
• IN Requests input from the user and stores into calculator. Resets the negative flag
• OUT Outputs whatever is in the calculator
• HLT End the program, resetting program counter to 0
• DAT <value> The mailbox of the data instruction is instead used to store value, this value is expected to be at most a 3-digit integer. You can omit the value to leave the mailbox uninitialised (storing 0)

Behaviours

Important

• The value in the calculator is not reset between tests (as in LMC), so if you assume the calculator stores the value 0 when your program starts, but you don't reset it yourself, every subsequent test after the first will be wrong
• After the HLT instruction the program counter is reset to 0, so the next instruction executed will be the first mailbox/instruction
• Negative flag is only reset when a new value is loaded into the calculator through LDA or IN
• You can reference an exact mailbox (to jump to, or store data in) using _mailboxNumber (e.g. BR _2 will jump to the 3rd mailbox)

Mostly esoteric (ignore)

• You can jump to a DAT which will execute the data you specified as if it were an instruction. You can also load an instruction's opcode and operand into the calculator as if it were some regular data
• The HLT instruction ignores its operand, so you could store a 2 digit number in the last 2 digits of the HLT command 0xx
• Any instruction with opcode 9 that isn't proceeded by either 01 (input) or 02 (output) is considered a NO-OP (just skipped)