72 lines
No EOL
2 KiB
C++
72 lines
No EOL
2 KiB
C++
#include "spec_helper.h"
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#include "build_tables/first_set.h"
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using std::set;
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using namespace build_tables;
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using namespace rules;
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START_TEST
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describe("computing FIRST sets", []() {
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const Grammar null_grammar("", {{ "something", blank() }});
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describe("for a sequence AB", [&]() {
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it("ignores B when A cannot be blank", [&]() {
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auto rule = seq({ sym("x"), sym("y") });
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AssertThat(first_set(rule, null_grammar), Equals(set<Symbol>({
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Symbol("x"),
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})));
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});
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it("includes FIRST(B) when A can be blank", [&]() {
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auto rule = seq({
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choice({
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sym("x"),
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blank() }),
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sym("y") });
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AssertThat(first_set(rule, null_grammar), Equals(set<Symbol>({
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Symbol("x"),
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Symbol("y")
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})));
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});
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it("includes FIRST(A's right hand side) when A is a non-terminal", [&]() {
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auto rule = choice({
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seq({
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sym("A"),
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sym("x"),
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sym("A") }),
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sym("A") });
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Grammar grammar("A", {
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{ "A", choice({
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seq({
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sym("y"),
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sym("z"),
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sym("y") }),
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sym("y") }) }
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});
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AssertThat(first_set(rule, grammar), Equals(set<Symbol>({
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Symbol("y")
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})));
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});
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it("includes FIRST(B) when A is a non-terminal and its expansion can be blank", [&]() {
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Grammar grammar("A", {{ "A", choice({ sym("x"), blank() }) }});
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auto rule = seq({
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sym("A"),
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sym("y") });
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AssertThat(first_set(rule, grammar), Equals(set<Symbol>({
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Symbol("x"),
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Symbol("y")
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})));
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});
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});
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});
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END_TEST |