Universal conversion to pointer

[joelreymont]

Assuming I have a recursive grammar that matches this AST

const BoolExprType = enum {
    defined_id,
    binary_expr,
    paren_expr,
    not_expr,
};

const BoolExpr = union(BoolExprType) {
    defined_id: []const u8,
    binary_expr: *BinaryBoolExpr,
    paren_expr: *BoolExpr,
    not_expr: *BoolExpr,
};

const BinaryBoolExpr = struct {
    lhs: BoolExpr,
    op: u8,
    rhs: BoolExpr,
};

Is there a universal conversion function that will return a pointer to whatever the parser returns, assuming parsing success?

[joelreymont]

There's the approach with the conversion function in #51 but I like mecha.unionInit and would hate to create the union by hand like that ticket does.

[Hejsil]

Is there a universal conversion function that will return a pointer to whatever the parser returns.

I assume you mean a function that will take an object and put it on the heap, giving you a pointer to that object. No, such a function does not exists currently

[joelreymont]

Is it possible to write such a function in Zig?

…

On Mon, 28 Oct 2024 at 14:03, Komari Spaghetti ***@***.***> wrote: Is there a universal conversion function that will return a pointer to whatever the parser returns. I assume you mean a function that will take an object and put it on the heap, giving you a pointer to that object. No, such a function does not exists currently — Reply to this email directly, view it on GitHub <#68 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAAESZ7XNJUVCPCVUG2NGMLZ5YKXNAVCNFSM6AAAAABQXH3TPGVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDINBRGM4TINBXG4> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[joelreymont]

This works!

Would it be a good addition to Mecha?

fn toPtr(comptime T: type) fn (std.mem.Allocator, T) anyerror!*T {
    return struct {
        fn toPtr(allocator: std.mem.Allocator, value: T) !*T {
            const result = try allocator.create(T);
            result.* = value;
            return result;
        }
    }.toPtr;
}

test "toPtr" {
    const allocator = testing.allocator;

    const Foo = struct {
        bar: u32,
        baz: u32,
    };

    const conv = toPtr(Foo);
    const value = Foo{ .bar = 10, .baz = 20 };
    const ptr = try conv(allocator, value);
    defer allocator.destroy(ptr);
    try testing.expectEqual(value, ptr.*);
}