parse.c

#include "9cc.h"

Node *new_node(NodeKind kind, Node *lhs, Node *rhs)
{
    Node *node = calloc(1, sizeof(Node));
    node->kind = kind;
    node->lhs = lhs;
    node->rhs = rhs;
    return node;
}

Node *new_node_num(int val)
{
    Node *node = calloc(1, sizeof(Node));
    node->kind = ND_NUM;
    node->val = val;
    return node;
}

Node *expr()
{
    Node *node = equality();

    for (;;)
    {
        if (consume("+"))
            node = new_node(ND_ADD, node, equality());
        else if (consume("-"))
            node = new_node(ND_SUB, node, equality());
        else
            return node;
    }
}

Node *equality()
{
    Node *node = relational();

    for (;;)
    {
        if (consume("=="))
            node = new_node(ND_EQ, node, relational());
        else if (consume("!="))
            node = new_node(ND_NE, node, relational());
        else
            return node;
    }
}

Node *relational()
{
    Node *node = add();
    for (;;)
    {
        if (consume("<"))
            node = new_node(ND_LT, node, add());
        else if (consume("<="))
            node = new_node(ND_LE, node, add());
        else if (consume(">"))
            node = new_node(ND_LT, add(), node);
        else if (consume(">="))
            node = new_node(ND_LE, add(), node);
        else
            return node;
    }
}

Node *add()
{
    Node *node = mul();

    for (;;)
    {
        if (consume("+"))
            node = new_node(ND_ADD, node, mul());
        else if (consume("-"))
            node = new_node(ND_SUB, node, mul());
        else
            return node;
    }
}

Node *mul()
{
    Node *node = unary();

    for (;;)
    {
        if (consume("*"))
            node = new_node(ND_MUL, node, unary());
        else if (consume("/"))
            node = new_node(ND_DIV, node, unary());
        else
            return node;
    }
}

Node *primary()
{
    // 次のトークンが"("なら、"(" expr ")"のはず
    if (consume("("))
    {
        Node *node = expr();
        expect(')');
        return node;
    }

    // そうでなければ数値のはず
    return new_node_num(expect_number());
}

Node *unary()
{
    if (consume("+"))
        return primary();
    if (consume("-"))
        return new_node(ND_SUB, new_node_num(0), unary());
    return primary();
}