Parser – Immediate Commands (Implementation)

Immediate Commands will be parsed in the separate function get_command(), which will be called only for the first token on the line (when the column is zero). The entire command will be parsed including the command's arguments, and the entire command will be put into a single token. If the line does not contain a valid command, the Parser will proceed to the other functions from the beginning of the line. The commands are one of the forms:

    Blank        Command has no arguments
    Line         Command has a line number
    Range  Command has a line number range
    Line-Incr  Command has a line number and an increment
    Range-Incr  Command has a line number range, a start line and an increment
    String  Command has a string argument

There will be an field in the Table for each of the immediate commands that will contain flags to which forms each command supports. The first thing get_command() will do is search the Table for the letter command to see if it is a valid command. If it is, then get_command() will proceed to parse the rest of the line looking for one of the above forms for the arguments. The separate function scan_command() will be called to actually scan and parse the arguments . This will make it easy to return immediately when the command is fully parsed or an error is found. After the arguments are parsed and the command syntax is good, the table will be search again for the command letter and the form of the arguments found to see if it is a valid command syntax.