Parser – Immediate Commands

As the new Table class was being designed, I realized that the immediate commands were forgotten. These are temporary until the GUI is implemented. Therefore, these will be implemented the simplest way. Back when I developed programs on GW-Basic, there was an add-on to the Basic that supplied some convenience features, specifically being able to use one character commands like L for LIST, E for EDIT, S for save. The temporary immediate commands will be implemented this way. There will be white space allowed in the commands and must be of one of several different forms to be recognized as an immediate command. The one character will be at the beginning of the line, the forms will be:

    LIST:  L  Lxxx  Lxxx-yyy
    EDIT:  E  Exxx
    DELETE:  Dxxx  Dxxx-yyy
    RUN:  R
    RENUM:   Rxxx-yyy  Rxxx-yyy,zz  Rxxx-yyy,nnn,zz
    SAVE:  S  S"fff"
    LOAD:  L"fff"
    NEW:  N
    AUTO:  A  Axxx  A,zz  Axxx,zz
    CONT:  C
    QUIT:  Q

Where xxx is a line number, xxx-yyy is a line number range (where xxx and/or yyy is optional), nnn is a new line number (optional), zz is an increment (optional) and fff is a file name. Note that some of the same letters are used for different commands (RUN/RENUM, LIST/LIST). Which one can be determined by the arguments provided.  There are three new commands that weren't included previously: AUTO (to automatically provided line numbers when entering program lines), CONT (to continue running the program after a break) and QUIT (to exit). If the line entered doesn't match one of these forms exactly, it will be processed by the regular Parser functions (consider the line L100=4, which is an immediate assignment, not a LIST command).

Several of the commands will do a check before they are executed. For RUN, LOAD, NEW and QUIT, if the program is not saved then there will be a prompt asking if the program should be saved first. For SAVE, S by itself will save the program using the current program name (from either a LOAD or the last S"fff" command, otherwise there will be a prompt for a file name).

One last thing, I decided to allow string constants to be terminated by the end of the line, in other words, no closing double-quote. GW-Basic works this way. Also convenient for LOAD and SAVE for just entering L"fff and S"fff. This requires just small change to the get_string() function – just don't return an error token for this condition. For program lines, when one of these unterminated string constants are recreated, the closing double-quote will be there.