• Akim Demaille's avatar
    is-valid: make the difference between invalid, and cannot-tell · 8458ab36
    Akim Demaille authored
    Currently to check if an expression is invalid, we compute its
    constant-term and catch errors: indeed `1*` will fail.
    Unfortunately constant-term can also fail because of operators
    it does not support, such as @ and {\}.  We must tell the difference.
    See issue #60.
    * vcsn/algos/constant-term.hh: Report errors for compose too.
    * vcsn/algos/is-valid-expression.hh: Improve error messages.
    * tests/bin/test.py: Improve error messages.
    * tests/python/constant-term.py:
    * tests/python/is-valid.py: Prefer q to r.
    Check more cases.