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cex: always show ε/%empty in counterexamples

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On a case such as
    %%
    exp
    : empty "a"
    | "a" empty

    empty
    : %empty

we used to display

    warning: shift/reduce conflict on token "a" [-Wcounterexamples]
    Example: • "a"
    Shift derivation
      exp
      ↳ 2: • "a" empty
                 ↳ 2: ε
    Example: • "a"
    Reduce derivation
      exp
      ↳ 1: empty  "a"
           ↳ 3: •

where the shift derivation shows an item "2: empty → ε", with an
explicit "ε", but the reduce derivation shows "3: empty → •", without
"ε".

For consistency, let's always show ε/%empty in rules with an empty
rhs:

    Reduce derivation
      exp
      ↳ 1: empty    "a"
           ↳ 3: ε •

* src/derivation.c (derivation_width, derivation_print_tree_impl):
Always show ε/%empty in counterexamples.
* tests/diagnostics.at: Check that case.
* tests/conflicts.at, tests/counterexample.at: Adjust.
This commit is contained in:
Akim Demaille
2020-08-31 07:22:17 +02:00
parent 82d913741b
commit 325ec7d324
6 changed files with 141 additions and 66 deletions
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14
src/derivation.c
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@@ -245,6 +245,13 @@ derivation_width (const derivation *deriv)
children_width += empty_width;
else
{
if (gl_list_size (deriv->children) == 1
&& gl_list_get_first (deriv->children) == &d_dot)
{
children_width += empty_width;
children_width += derivation_separator_width;
}
derivation *child;
for (gl_list_iterator_t it = gl_list_iterator (deriv->children);
derivation_list_next (&it, &child);
@@ -310,6 +317,13 @@ derivation_print_tree_impl (const derivation *deriv, FILE *out,
res += fputs_if (depth == 1, out, padding, empty);
else
{
if (gl_list_size (deriv->children) == 1
&& gl_list_get_first (deriv->children) == &d_dot)
{
res += fputs_if (depth == 1, out, padding, empty);
res += fputs_if (depth == 1, out, padding, derivation_separator);
}
bool first = true;
derivation *child;
for (gl_list_iterator_t it = gl_list_iterator (deriv->children);