Keszeg 4 Language Documentation

Keszeg 4 is a simple interpreted language supporting variables, arrays, functions, references, and basic I/O and arithmetic operations.

---

Function Declarations

Functions are declared using FUN and ended with EF.
Parameters are declared after the function name, using @ for value parameters and & for reference parameters, followed by the name and type.

Reference parameter example:

FUN SWAP & A INT & B INT
        @ TEMP INT
        TEMP = A
        A = B
        B = TEMP
    EF

Value parameter example:

FUN ADD @ X INT @ Y INT
        @ RESULT INT
        RESULT = X + Y
        print $ RESULT
    EF

---

Variables

Variables are declared with @ name TYPE. Supported types: INT, FLOAT, BYTE, IARRAY, FARRAY, STRING.

@ X INT
    @ ARR IARRAY

---

References

Reference parameters allow passing variables by reference to functions. Use & name TYPE in the function declaration. When calling, pass the variable name.

FUN INCREMENT & X INT
        X += 1
    EF

    CALL INCREMENT X

---

Instructions

Assignment

• X = 5 - Assigns 5 to X.
• X = Y - Assigns value of Y to X.

Arithmetic

• X = Y + Z - Adds Y and Z, stores in X.
• X = Y - Z
• X = Y * Z
• X = Y / Z
• X = Y % Z
• X += Y, X -= Y, X *= Y, X /= Y, X %= Y

Arrays

• ARR : 2 <- 10 - Sets ARR[2] to 10.
• X <- ARR : 2 - Loads ARR[2] into X.
• X sizeof ARR - Stores size of ARR in X.
• free ARR - Clears array contents.

String Operations

• cat stringvar const Hello - Appends "Hello" to stringvar.
• cat stringvar string othervar - Appends contents of othervar to stringvar.

Input/Output

• print $ X - Prints X numerically.
• print ascii X - Prints X as ASCII character.
• print string STR - Prints string variable.
• print const Hello - Prints "Hello".
• println ... - Same as print, but adds newline.
• input $ X - Reads numeric input into X.
• input ascii X - Reads a character into X.
• input string STR - Reads a line into string variable.
• clear - Clears the screen.
• print serial X - [Mulloway] Sends contents of X string to serial COM1 output
• input serial X [Y] - [Mulloway] Reads Y bytes to X string from serial COM1 port. If Y is not present, it reads all currently available bytes.
• print usb STR - [Mulloway] Sends string STR to USB serial output.
• input usb X [Y] - [Mulloway] Reads Y bytes from USB serial to X string. Blocks until data is available. If Y is not present, it reads all currently available bytes.

File Operations

• save iarray ARR path - Saves integer array to file.
• load iarray ARR path - Loads integer array from file.
• save string STR path - Saves string to file.
• load string STR path - Loads string from file.

Control Flow

• if X = Y ... end
• while X < Y ... end

Function Calls

• call FUNC X Y - Calls FUNC with arguments X and Y.
• X <- call FUNC Y Z - Calls FUNC with Y, Z, stores return value in X.

Return

• return X - Returns value X from function.

Random

• random X 10 - Sets X to random integer in [0, 10).

Sleep

• sleep 1000 - Pauses execution for 1000 milliseconds.

Exec

• exec const ls -l - Executes a command based on the interpreter's environment.
• exec string STR - Executes command from string variable.

---

Syntax Notes

Comments

Any text after a # character on a line is treated as a comment and ignored by the interpreter.

Escaped Characters

In string constants, you can use escape sequences:

• \n for newline
• \t for tab
• \s for space
• \h for #
• \c for ,
• Uppercase versions like \N, \T, etc. are also supported.

Multiple Instructions per Line

You can write multiple instructions on a single line by separating them with a comma ,.

---

Notes

• All variable, function, type and instruction names are case-insensitive.
• Execution always starts from the main function.