Re: about syntax trees

On Mar 19, 8:40 pm, chinlu chinawa <chinluchin...@yahoo.co.uk> wrote:
> Hello,
>
> I'm relatively new to parsing. I've managed to code a
> recursive-descent ll(1) parser in c (thus, a
> stack/table based one). My question is about syntax
> trees.
>
> If I trace each accepting operation with a printf,
> this is what I get for the expression: a+b*c
>
> accept on: a
> accept on: +
> accept on: b
> accept on: *
> accept on: c
>
> However I can see ast's being more like this all over
> the place:
>
> +
> /|\
> b | a
> *
> c
>
> But I cannot think of a way you get exactly this, any
> pointers or advises? thanks so much.


You could use something like this:


struct node {
    int tag;
    char* value;
    struct node* left;
    struct node* right;
}


struct node a = { ID, "a", NULL,NULL };
struct node b = { ID, "b", NULL,NULL };
struct node b = { ID, "c", NULL,NULL };
struct node op2 = { BINOP, "*", &b, &c };
struct node op1 = { BINOP, "+", &a, &op2 };


Resulting in a list like this:
    (+ a (* b c))

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