def autoIndentBlock(self, block, char = '\n'):
        """Indent block after Enter pressed or trigger character typed
        """
        cursor = QTextCursor(block)
        currentText = block.text()
        spaceAtStartLen = len(currentText) - len(currentText.lstrip())
        currentIndent = currentText[:spaceAtStartLen]
        indent = self._smartIndenter.computeIndent(block, char)
        if indent is not None and indent != currentIndent:
            self._qpart.replaceText(block.position(), spaceAtStartLen, indent)
def test_lens_formula():
    u, v, f = symbols('u, v, f')
    assert lens_formula(focal_length=f, u=u) == f*u/(f + u)
    assert lens_formula(focal_length=f, v=v) == f*v/(f - v)
    assert lens_formula(u=u, v=v) == u*v/(u - v)
    assert lens_formula(u=oo, v=v) == v
    assert lens_formula(u=oo, v=oo) is oo
    assert lens_formula(focal_length=oo, u=u) == u
    assert lens_formula(u=u, v=oo) == -u
    assert lens_formula(focal_length=oo, v=oo) is -oo
    assert lens_formula(focal_length=oo, v=v) == v
    assert lens_formula(focal_length=f, v=oo) == -f
    assert lens_formula(focal_length=oo, u=oo) is oo
    assert lens_formula(focal_length=oo, u=u) == u
    assert lens_formula(focal_length=f, u=oo) == f
    raises(ValueError, lambda: lens_formula(focal_length=f, u=u, v=v))