Translator – Expression Type (New Design)

The new design for the rest of the data type error detection consists of remembering the token of the first operand of each sub-expression within an expression, so that an error can be reported against this token when a data type error is detected. Consider this invalid assignment statement:

Z% = A$ + B$ + C$

Currently this reports an “expected numeric value” at the second + operator. It should report “expected numeric expression” at the A$ token. However, the detection can't occur at the A$ token before the entire expression is processed. Consider this valid assignment statement:

Z% = A$ + B$ > C$

The expression becomes an integer at the > operator, therefore an “expected numeric expression” can't be reported at the A$ token.

Each binary operator token appended to the output is also pushed onto the done stack, replacing it's operands. The token of the first operand of the operator will be attached to the operator when it is pushed to the done stack. If the first operand is another operator, then this operator's first operand is attached (in other words, the operator will inherit the first operand's first operand if there is one).