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const std = @import("std");
const parser = @import("parser.zig");
const EvaluatorError = error{
EvaluationError,
OutOfMemory,
};
pub const Evaluator = struct {
ast: ?*parser.Node,
variables: std.StringHashMap(?i64),
//TODO: CREATE STACK WITH SCOPES AND WE CAN SEARCH UP SCOPES
allocator: std.mem.Allocator,
pub fn init(allocator: std.mem.Allocator) !*Evaluator {
const evaluator = try allocator.create(Evaluator);
evaluator.* = .{
.ast = null,
.variables = std.StringHashMap(?i64).init(allocator),
.allocator = allocator,
};
return evaluator;
}
pub fn deinit(self: *Evaluator) void {
self.variables.deinit();
self.allocator.destroy(self);
}
pub fn evaluate_ast(self: *Evaluator, ast: *parser.Node) !i64 {
errdefer std.debug.print("Error evaluating AST\n", .{});
std.debug.assert(ast.* == parser.Node.PROGRAM);
self.ast = ast;
const main = self.find_function("main") orelse return EvaluatorError.EvaluationError;
return try self.evaluate_function_definition(main);
}
fn evaluate_statement(self: *Evaluator, statement: *parser.Node) EvaluatorError!void {
errdefer std.debug.print("Error evaluating statement\n", .{});
std.debug.assert(statement.* == parser.Node.STATEMENT);
return switch (statement.STATEMENT.statement.*) {
.ASSIGNMENT_STATEMENT => |*assignment_statement| try self.evaluate_assignment_statement(@ptrCast(assignment_statement)),
.PRINT_STATEMENT => |*print_statement| try self.evaluate_print_statement(@ptrCast(print_statement)),
.FUNCTION_CALL_STATEMENT => |*function_call_statement| _ = try self.evaluate_function_call_statement(@ptrCast(function_call_statement)),
else => unreachable,
};
}
fn evaluate_assignment_statement(self: *Evaluator, node: *parser.Node) !void {
errdefer std.debug.print("Error evaluating assignment statement\n", .{});
std.debug.assert(node.* == parser.Node.ASSIGNMENT_STATEMENT);
const assignment_statement = node.ASSIGNMENT_STATEMENT;
//TODO: We should lowercase keys no?
if (assignment_statement.is_declaration) {
try self.variables.put(assignment_statement.name, null);
}
if (!self.variables.contains(assignment_statement.name)) {
std.debug.print("Variable not found: {s}\n", .{assignment_statement.name});
return EvaluatorError.EvaluationError;
}
const val = try self.get_expression_value(assignment_statement.expression);
try self.variables.put(assignment_statement.name, val);
}
fn evaluate_print_statement(self: *Evaluator, print_statement: *parser.Node) !void {
errdefer std.debug.print("Error evaluating print statement\n", .{});
std.debug.assert(print_statement.* == parser.Node.PRINT_STATEMENT);
const print_value = try self.get_expression_value(print_statement.PRINT_STATEMENT.expression);
std.debug.print("PRINT: {d}\n", .{print_value});
}
fn evaluate_function_call_statement(self: *Evaluator, function_call_statement: *parser.Node) !i64 {
errdefer std.debug.print("Error evaluating function call statement\n", .{});
std.debug.assert(function_call_statement.* == parser.Node.FUNCTION_CALL_STATEMENT);
const val = self.variables.get(function_call_statement.FUNCTION_CALL_STATEMENT.name) orelse return EvaluatorError.EvaluationError;
return val.?;
}
fn evaluate_return_statement(self: *Evaluator, return_statement: *parser.Node) !i64 {
errdefer std.debug.print("Error evaluating return statement\n", .{});
std.debug.assert(return_statement.* == parser.Node.RETURN_STATEMENT);
const return_value = try self.get_expression_value(return_statement.RETURN_STATEMENT.expression);
return return_value;
}
fn get_expression_value(self: *Evaluator, node: *parser.Node) !i64 {
errdefer std.debug.print("Error getting statement value\n", .{});
switch (node.*) {
.ADDITIVE_EXPRESSION => |x| {
const lhs = try self.get_expression_value(x.lhs);
const rhs = try self.get_expression_value(x.rhs);
return lhs + rhs;
},
.PRIMARY_EXPRESSION => |x| {
switch (x) {
.NUMBER => |number| return number.value,
.IDENTIFIER => |identifier| {
const val = self.variables.get(identifier.name) orelse {
std.debug.print("Identifier {any} not found\n", .{identifier.name});
return EvaluatorError.EvaluationError;
};
return val.?;
},
else => unreachable,
}
},
.FUNCTION_CALL_STATEMENT => |x| {
const func = self.find_function(x.name) orelse return EvaluatorError.EvaluationError;
return try self.evaluate_function_definition(func);
},
else => unreachable,
}
}
fn evaluate_function_definition(self: *Evaluator, node: *parser.Node) EvaluatorError!i64 {
errdefer std.debug.print("Error evaluating function definition\n", .{});
std.debug.assert(node.* == parser.Node.FUNCTION_DEFINITION);
const function_definition = node.*.FUNCTION_DEFINITION;
var i: usize = 0;
while (i < function_definition.statements.len - 1) {
const stmt = function_definition.statements[i];
try self.evaluate_statement(stmt);
i += 1;
}
const return_stmt = function_definition.statements[i];
return try self.evaluate_return_statement(return_stmt);
}
fn find_function(self: *Evaluator, name: []const u8) ?*parser.Node {
errdefer std.debug.print("Error finding main function\n", .{});
std.debug.assert(self.ast.?.* == parser.Node.PROGRAM);
for (self.ast.?.PROGRAM.statements) |*statement| {
const x = statement.*.STATEMENT.statement;
if (x.* != parser.Node.ASSIGNMENT_STATEMENT) continue;
const y = x.*.ASSIGNMENT_STATEMENT;
if (y.is_declaration and std.mem.eql(u8, y.name, name)) {
return y.expression;
}
}
return null;
}
};
test "simple" {
const ast = &parser.Node{ .PROGRAM = .{ .statements = @constCast(&[_]*parser.Node{ @constCast(&parser.Node{ .STATEMENT = .{ .statement = @constCast(&parser.Node{ .VARIABLE_STATEMENT = .{
.is_declaration = true,
.name = @constCast("i"),
.expression = @constCast(&parser.Node{ .EXPRESSION = .{
.NUMBER = .{ .value = 2 },
} }),
} }) } }), @constCast(&parser.Node{ .STATEMENT = .{ .statement = @constCast(&parser.Node{
.VARIABLE_STATEMENT = .{
.is_declaration = false,
.name = @constCast("i"),
.expression = @constCast(&parser.Node{ .EXPRESSION = .{
.NUMBER = .{ .value = 2 },
} }),
},
}) } }) }) } };
var evaluator = try Evaluator.init(std.testing.allocator);
defer evaluator.deinit();
const evaluation_result = try evaluator.evaluate_ast(@constCast(ast));
try std.testing.expectEqual(0, evaluation_result);
}
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