Translator Class – Table/Parser Changes

The new unary operator Neg_Code for Sub_Code needs to be added, which will represent negation, along with it's corresponding table entry. To other two codes also need to be added, Null_Code and EOL_Code.

The Null_Code will be used for two things. One being a very low (lowest) precedence operator that will be pushed onto the operator stack before processing tokens. This will simplify the Translator when it is checking and popping off high precedence operators as it won't need to check if the stack is empty first. The second will be for the new unary_code field that needs to be added to the Table entries to indicate an operator's associated unary operator with Null_Code indicating that there is no unary operator.

The Parser needs to be modified to return a token with an EOL_Code at the end of the line instead of returning a NULL pointer. The reason for this changes is so that this EOL token can be passed into the Translator. The EOL will be treated as an operator and it's precedence will also be very low, but higher than the Null operator. The EOL operator will force the Translator to empty the operator stack of any operators except for the Null operator. Also by using the EOL operator, the Translator can make sure an end of line is allowed. In other words, if the Translator is expecting an operand (as after it has just seen an operator), but sees EOL (an operator), an error will be reported (“operand expected”).