Syntactical Checks

With regard to the syntax detailed in the previous section, COBA 2.0 informs users of syntactically malformed input formulas by showing informative error messages.

Consider, as examples, the syntactically malformed input strings q), q+, p^, p', (p, (p&(q), (p+q&), and (+q). The following error messages are generated.

• The illegal literal q) contains a parenthesis.
• The illegal literal q+ has a reserved logical symbol.
• The illegal literal p^ has the reserved symbol ^.
• The illegal literal p' has the reserved symbol '.
• (p has no matching closing parenthesis.
• (p&(q) has one or more unmatched parentheses.
• (p+q&) has no matching right operand for &.
• (+q) has no matching left operand for +.