/* Program extracts from Chapter 13 of
uint16_t expr_evaluate(struct expr* e, uint16_t(*labelreplace)(bstring label), void(*errexit)(int code, void* data))
{
uint16_t t;
switch (e->type)
{
case EXPR_NUMBER:
return (uint16_t)(intptr_t)e->data;
case EXPR_LABEL:
if (labelreplace == NULL)
{
errexit(EXPR_EXIT_LABEL_NOT_FOUND, (bstring)e->data);
return 0;
}
else
return labelreplace((bstring)e->data);
case EXPR_EXPR:
switch (e->op)
{
case EXPR_OP_ADD:
return recursive_evaluate(e->a) + recursive_evaluate(e->b);
case EXPR_OP_SUBTRACT:
return recursive_evaluate(e->a) - recursive_evaluate(e->b);
case EXPR_OP_MULTIPLY:
return recursive_evaluate(e->a) * recursive_evaluate(e->b);
case EXPR_OP_DIVIDE:
t = recursive_evaluate(e->b);
if (t == 0)
errexit(EXPR_EXIT_DIVIDE_BY_ZERO, expr_representation(e->b));
return recursive_evaluate(e->a) / t;
case EXPR_OP_MODULUS:
t = recursive_evaluate(e->b);
if (t == 0)
errexit(EXPR_EXIT_DIVIDE_BY_ZERO, expr_representation(e->b));
return recursive_evaluate(e->a) % t;
case EXPR_OP_EQUALS:
return recursive_evaluate(e->a) == recursive_evaluate(e->b);
case EXPR_OP_NOT_EQUALS:
return recursive_evaluate(e->a) != recursive_evaluate(e->b);
case EXPR_OP_LESS_THAN:
return recursive_evaluate(e->a) < recursive_evaluate(e->b);
case EXPR_OP_LESS_EQUALS:
return recursive_evaluate(e->a) <= recursive_evaluate(e->b);
case EXPR_OP_GREATER_THAN:
return recursive_evaluate(e->a) > recursive_evaluate(e->b);
case EXPR_OP_GREATER_EQUALS:
return recursive_evaluate(e->a) >= recursive_evaluate(e->b);
case EXPR_OP_AND:
return recursive_evaluate(e->a) & recursive_evaluate(e->b);
case EXPR_OP_BOR:
return recursive_evaluate(e->a) | recursive_evaluate(e->b);
case EXPR_OP_XOR:
return recursive_evaluate(e->a) ^ recursive_evaluate(e->b);
default:
return 0;
}
default:
return 0;
}
}
