Init commit

mexigo/interpreter/codeline.go

@@ -0,0 +1,6 @@
+package interpreter
+
+type Codeline struct {
+	Linenumber int
+	Code string
+}

mexigo/interpreter/debug.go

@@ -0,0 +1,20 @@
+package interpreter
+
+import (
+	"fmt"
+	"log"
+)
+
+func (t *Tape) DebugPrintTape() {
+	log.Printf("Tape is currently %d cells big", len(t.cells))
+	for i, v := range t.cells {
+		fmt.Printf("Cell %d: %d (%c)\n", i, v, v)
+	}
+}
+
+func (s * Stack) DebugPrintStack() {
+	log.Printf("Stack is currently %d entries big", len(s.values))
+	for i, v := range s.values {
+		fmt.Printf("Stack row %d: %d (%c)\n", i, v, v)
+	}
+}

mexigo/interpreter/interpreter.go

@@ -0,0 +1,89 @@
+package interpreter
+
+import (
+	"fmt"
+	"github.com/pkg/errors"
+)
+
+type Interpreter struct {
+	machine Machine
+	program []Codeline
+	programCounter int
+	programPointer int
+}
+
+// Feeds a new mexico machine with given code.
+func Run(commands []Codeline) error {
+	var i Interpreter
+
+	// Set the given code as commands for the interpreter
+	setCmdErr := i.SetCommands(commands)
+	if setCmdErr != nil {
+		return setCmdErr
+	}
+
+	// Let's run this program :)
+	return i.Run()
+}
+
+// Sets the given array as new program for the interpreter
+func (i *Interpreter) SetCommands(commands []Codeline) error {
+	i.program = commands
+	i.programCounter = 0
+	return i.GoToNextCommand()
+}
+
+// Searches for the next command, starting from the current value of the programCounter.
+// This may sound odd, because in most other architectures, this is just programCounter++, and there would be no need
+// for a function like this. However, mexico has a BASIC-style program line numbering, means we need to search for the
+// next line number containing code, because there may be one or more empty lines between the current and the next line.
+// This is exactly what GoToNextCommand() does.
+// If there is no next command, most likely because we reached the end of the program, an error is thrown.
+func (i *Interpreter) GoToNextCommand() error {
+	// Iterate over all lines to find the first which has a greater line number than the current one
+	for index, line := range i.program {
+		if line.Linenumber >= i.programCounter {
+			// Found, set and return
+			i.programCounter = line.Linenumber
+			i.programPointer = index
+			return nil
+		}
+	}
+
+	// No next command found. Throw error.
+	return errors.New(fmt.Sprintf("Found no commands after line %d. Stopping.", i.programCounter))
+}
+
+// Runs the commands, unless an error is encountered, then it doesn't run the commands.
+func (i *Interpreter) Run() error {
+	defer i.machine.Tape.DebugPrintTape()
+	defer i.machine.Stack.DebugPrintStack()
+
+	for {
+		// Get current command
+		cmd := i.program[i.programPointer]
+
+		// Run command in the machine
+		jumpLine, doJump, runErr := i.machine.RunCommand(cmd.Code)
+		if runErr != nil {
+			// Encountered an error during runtime, stop execution
+			return runErr
+		}
+
+		// Check if we should jump anywhere else than to the next code line
+		if doJump {
+			// Yes, do it then.
+			i.programCounter = jumpLine
+		} else {
+			// We are not asked to jump anywhere, move on to the next code line then.
+			i.programCounter++
+		}
+
+		// Skip empty lines if there are any.
+		nextCmdErr := i.GoToNextCommand()
+		if nextCmdErr != nil {
+			// Encountered error finding the next command, throw it
+			return nextCmdErr
+		}
+	}
+}

mexigo/interpreter/machine.go

@@ -0,0 +1,160 @@
+package interpreter
+
+import (
+	"fmt"
+	"github.com/pkg/errors"
+	"os"
+	"strconv"
+	"strings"
+)
+
+type Machine struct {
+	Stack Stack
+	Tape Tape
+}
+
+// Runs the given command.
+// Returns the next line (comparable to the 'Program Counter') to be executed, but just if doJump is true.
+// May also return an error. It's advised to stop the execution of further commands if this command throws an error.
+func (m *Machine) RunCommand(cmd string) (jumpLine int, doJump bool, execErr error) {
+	// Let's check which command we are told to run.
+	if cmd == "left" {
+		// Moves the tape head one cell to the left
+		m.Tape.MoveLeft()
+	} else if cmd == "right" {
+		// Moves the tape head one cell to the right
+		m.Tape.MoveRight()
+	} else if cmd == "pusht" {
+		// Reads the current cell value and pushes it on top of the stack
+		m.Stack.Push(m.Tape.Get())
+	} else if strings.HasPrefix(cmd, "push ") {
+		// Pushes the value n to the stack
+
+		// Cut "push " away and trim
+		strVal := strings.Trim(cmd[5:], " ")
+
+		// Convert to integer
+		intVal, atoiErr := strconv.Atoi(strVal)
+		if atoiErr != nil {
+			// Conversion failed.
+			execErr = errors.New(fmt.Sprintf("Tried to push non-integer value '%s' to the stack. %s", strVal, atoiErr.Error()))
+			return
+		} else {
+			// Conversion successful, push constant
+			m.Stack.Push(intVal)
+		}
+	} else if cmd == "pop" {
+		// Pops top stack value to the current cell
+		m.Tape.Set(m.Stack.Pop())
+	} else if cmd == "dup" {
+		// Duplicates the topmost stack value
+		val := m.Stack.Pop()
+		m.Stack.Push(val)
+		m.Stack.Push(val)
+	} else if cmd == "del" {
+		// Deletes the topmost stack value, ignoring its value
+		m.Stack.Pop()
+	} else if cmd == "eq" {
+		// Checks if stack[0] == stack[1]. Pushes 1 to the stack if equal, 0 otherwise
+		stack0 := m.Stack.Pop()
+		stack1 := m.Stack.Pop()
+
+		if stack0 == stack1 {
+			m.Stack.Push(1)
+		} else {
+			m.Stack.Push(0)
+		}
+	} else if cmd == "not" {
+		// Inverses stack[0]
+		stack0 := m.Stack.Pop()
+
+		if stack0 == 0 {
+			m.Stack.Push(1)
+		} else if stack0 == 1 {
+			m.Stack.Push(0)
+		} else {
+			// Not a binary number, not going to inverse it.
+			execErr = errors.New(fmt.Sprintf("Tried to inverse non-binary integer value '%d'", stack0))
+			return
+		}
+	} else if cmd == "gt" {
+		// Checks if stack[0] > stack[1]. Pushes 1 to the stack if greater, 0 otherwise
+		stack0 := m.Stack.Pop()
+		stack1 := m.Stack.Pop()
+
+		if stack0 > stack1 {
+			m.Stack.Push(1)
+		} else {
+			m.Stack.Push(0)
+		}
+	} else if cmd == "lt" {
+		// Checks if stack[0] < stack[1]. Pushes 1 to the stack if greater, 0 otherwise
+		stack0 := m.Stack.Pop()
+		stack1 := m.Stack.Pop()
+
+		if stack0 < stack1 {
+			m.Stack.Push(1)
+		} else {
+			m.Stack.Push(0)
+		}
+	} else if cmd == "add" {
+		// Calculates stack[0] + stack[1], and pushes the result to the stack
+		m.Stack.Push(m.Stack.Pop() + m.Stack.Pop())
+	} else if cmd == "sub" {
+		// Calculates stack[0] - stack[1], and pushes the result to the stack
+		m.Stack.Push(m.Stack.Pop() - m.Stack.Pop())
+	} else if cmd == "mult" {
+		// Calculates stack[0] * stack[1], and pushes the result to the stack
+		m.Stack.Push(m.Stack.Pop() * m.Stack.Pop())
+	} else if cmd == "div" {
+		// Calculates stack[0] / stack[1], and pushes the result to the stack
+		m.Stack.Push(m.Stack.Pop() / m.Stack.Pop())
+	} else if cmd == "mod" {
+		// Calculates stack[0] % stack[1], and pushes the result to the stack
+		m.Stack.Push(m.Stack.Pop() % m.Stack.Pop())
+	} else if cmd == "read" {
+		// Reads a character from the user, and pushes its char value to the stack
+		var readChar []byte
+
+		// Read character(s)
+		numChars, readErr := os.Stdin.Read(readChar)
+		if readErr != nil {
+			// Failed to read from stdin.
+			execErr = errors.New(fmt.Sprintf("Failed to read character from stdin: %s", readErr.Error()))
+			return
+		}
+
+		if numChars < 1 || readChar == nil {
+			// Didn't even read a single character.
+			execErr = errors.New("Failed to read character from stdin.")
+			return
+		}
+
+		// Push character to stack
+		m.Stack.Push(int(readChar[0]))
+
+		// Check if user typed more than asked for
+		if numChars > 1 {
+			// Ugh, what a spammer
+			execErr = errors.New("Read more than one character - ignoring all but the first character.")
+			return
+		}
+	} else if cmd == "print" {
+		// Prints stack[0] as a character
+		val := m.Stack.Pop()
+		fmt.Printf("%q (%d)\n", rune(val), val)
+	} else if cmd == "jmp" {
+		// Jumps to the line number specified by stack[0]
+		jumpLine = m.Stack.Pop()
+		doJump = true
+	} else if cmd == "jmpc" {
+		// Jumps to the line number specified by stack[0], if stack[1] is not 0.
+		jumpLine = m.Stack.Pop()
+		doJump = m.Stack.Pop() != 0
+	} else {
+		// ... no such command.
+		execErr = errors.New(fmt.Sprintf("Command not found: %s", cmd))
+	}
+
+	return
+}

mexigo/interpreter/stack.go

@@ -0,0 +1,27 @@
+package interpreter
+
+import "log"
+
+type Stack struct {
+	values []int
+}
+
+// Pushes the given value to the stack
+func (s *Stack) Push(val int) {
+	s.values = append(s.values, val)
+}
+
+// Pops the top element from the stack and return its value
+func (s *Stack) Pop() int {
+	// Check if the stack contains at least one element
+	if len(s.values) > 0 {
+		// There's at least one element, pop it: get value and delete element
+		val := s.values[len(s.values)-1]
+		s.values = s.values[:len(s.values)-1]
+		return val
+	}
+
+	// Stack is empty, but we should pop... Damn.
+	log.Panic("Tried to pop value from empty stack.")
+	return 0
+}

mexigo/interpreter/tape.go

@@ -0,0 +1,51 @@
+package interpreter
+
+type Tape struct {
+	head uint
+	cells []int
+}
+
+// Sets the head to point to the specified position
+func (t *Tape) SetHead(pos uint) {
+	t.GrowUpTo(pos)
+	t.head = pos
+}
+
+// Resizes the tape to the given size.
+// If the cell array is already bigger than the specified size, nothing happens.
+// If the cell array is smaller than the specified size, it's resized to the given size and filled with the value 0.
+func (t *Tape) GrowUpTo(size uint) {
+	if uint(len(t.cells)) > size {
+		// Tape is already bigger. Do nothing.
+		return
+	}
+
+	// Append as many zeroes as required.
+	for uint(len(t.cells)) <= size {
+		t.cells = append(t.cells, 0)
+	}
+}
+
+// Moves the tape head left
+func (t *Tape) MoveLeft() {
+	if t.head > 0 {
+		t.SetHead(t.head - 1)
+	}
+}
+
+// Moves the tape head left
+func (t *Tape) MoveRight() {
+	t.SetHead(t.head + 1)
+}
+
+// Returns the current cell value
+func (t *Tape) Get() int {
+	t.GrowUpTo(t.head)
+	return t.cells[t.head]
+}
+
+// Sets the current cell to the new value
+func (t *Tape) Set(newVal int) {
+	t.GrowUpTo(t.head)
+	t.cells[t.head] = newVal
+}