| 1 | const std = @import("std"); |
| 2 | const expectEqual = std.testing.expectEqual; |
| 3 | |
| 4 | const Instruction = enum { |
| 5 | add, |
| 6 | mul, |
| 7 | end, |
| 8 | }; |
| 9 | |
| 10 | fn evaluate(initial_stack: []const i32, code: []const Instruction) !i32 { |
| 11 | var buffer: [8]i32 = undefined; |
| 12 | var stack = std.ArrayList(i32).initBuffer(&buffer); |
| 13 | try stack.appendSliceBounded(initial_stack); |
| 14 | var ip: usize = 0; |
| 15 | |
| 16 | return vm: switch (code[ip]) { |
| 17 | // Because all code after `continue` is unreachable, this branch does |
| 18 | // not provide a result. |
| 19 | .add => { |
| 20 | try stack.appendBounded(stack.pop().? + stack.pop().?); |
| 21 | |
| 22 | ip += 1; |
| 23 | continue :vm code[ip]; |
| 24 | }, |
| 25 | .mul => { |
| 26 | try stack.appendBounded(stack.pop().? * stack.pop().?); |
| 27 | |
| 28 | ip += 1; |
| 29 | continue :vm code[ip]; |
| 30 | }, |
| 31 | .end => stack.pop().?, |
| 32 | }; |
| 33 | } |
| 34 | |
| 35 | test "evaluate" { |
| 36 | const result = try evaluate(&.{ 7, 2, -3 }, &.{ .mul, .add, .end }); |
| 37 | try expectEqual(1, result); |
| 38 | } |
| 39 | |
| 40 | // test |