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v/examples/brainvuck.v

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import os
fn main() {
if os.args.len < 2 {
eprintln('you need to supply a brainfuck program as a string argument')
exit(1) // exit with non-zero exit code if there is no program to run
}
program := os.args[1] // our program is fed in as a string
mut memory := []u8{len: 256} // we have 256 bytes of memory
mut address := u8(0) // as well as an 8-bit address register
mut stack := []int{} // our stack does not need a maximum length
mut program_counter := 0 // program counter
// interpreter starts here
for program_counter < program.len {
// we look at what the current character our program counter is seeing
match program[program_counter] {
`>` {
address++ // increment the address
}
`<` {
address-- // decrement the address
}
`+` {
memory[address]++ // increment the value at the address
}
`-` {
memory[address]-- // decrement the value at the address
}
`.` {
print(memory[address].ascii_str()) // print the value at the address
}
`,` {
input := os.input_opt('') or { '' } // read value and account for errors
memory[address] = input[0] // this is so we can ignore newlines
// because strings are 0-terminated, it also gives us a default value for free!
}
`[` {
stack << program_counter // add loop start address to the call stack
}
`]` {
if memory[address] != 0 {
// set the program counter to the last loop start
// so it jumps back and loops again
program_counter = stack[stack.len - 1]
} else {
// otherwise remove the address from the stack and continue
stack.pop()
}
}
else {
// the interpreter should ignore characters that are not part of the language
}
}
// increment the program counter to go to the next instruction
program_counter++
// back to line 20!
}
// print the state of the interpreter at the end
println('Address: $address')
println('Memory: $memory')
}