# NOT RUN {
# A predicate is provided to distinguish formulas from the
# colon-equals operator:
is_definition(quote(a := b))
is_definition(a ~ b)
# is_formulaish() tests for both definitions and formulas:
is_formulaish(a ~ b)
is_formulaish(quote(a := b))
# }
Run the code above in your browser using DataLab