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const std = @import("std");
const expectEqual = std.testing.expectEqual;
const Instruction = enum {
add,
mul,
end,
};
fn evaluate(initial_stack: []const i32, code: []const Instruction) !i32 {
var buffer: [8]i32 = undefined;
var stack = std.ArrayList(i32).initBuffer(&buffer);
try stack.appendSliceBounded(initial_stack);
var ip: usize = 0;
return vm: switch (code[ip]) {
// Because all code after `continue` is unreachable, this branch does
// not provide a result.
.add => {
try stack.appendBounded(stack.pop().? + stack.pop().?);
ip += 1;
continue :vm code[ip];
},
.mul => {
try stack.appendBounded(stack.pop().? * stack.pop().?);
ip += 1;
continue :vm code[ip];
},
.end => stack.pop().?,
};
}
test "evaluate" {
const result = try evaluate(&.{ 7, 2, -3 }, &.{ .mul, .add, .end });
try expectEqual(1, result);
}
// test
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