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Re: Constants

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  • midi_boink
    ... a
    Message 1 of 3 , Aug 1, 2003
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      --- In libertybasic@yahoogroups.com, "willieej2002"
      <willieej2002@y...> wrote:
      > Hello everyone. I am making a brand new language and I want it to
      > use constants similar to LB's.
      >
      > Is there some kind of command that will determine if the string is
      a
      > constant or will I have to define every single constant in windows?
      >
      > Help Please?
      >
      > ---
    • Tom Nally
      I think of a constant as a variable which holds a given value, and may never be assigned a new value. (Of course, if that s the case, it s not technically a
      Message 2 of 3 , Aug 2, 2003
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        I think of a "constant" as a variable which holds a given value, and
        may never be assigned a new value. (Of course, if that's the case,
        it's not technically a "variable", because the value will not vary,
        eh?)

        As an example, in your language you may want to establish a constant
        called "pi". Your users will be allowed to use the constant "pi" in
        an equation, but they will not be allowed to assign it a new value.

        How might this be accomplished?

        Well, when your users use your language, I suspose they will be
        writing "programs" or "scripts" with some kind of an editor. As the
        language author, I'm guessing that you will develop some kind of
        a "parser" which reads the script line by line, and word by word.
        When your parser comes upon the word "pi" (or any other constants
        that you've established), I expect that you will provide the user
        with an error message if "pi" is not used according to the
        syntactical rules that you've set.

        In short, I guess creating constants involves two steps: (1)
        assigning each constant a value in the "engine" of your programming
        language, and (2) protecting the constant against illegal use by the
        programmer when the program is parsed and compiled.

        ---Tom Nally, New Orleans






        --- In libertybasic@yahoogroups.com, "willieej2002"
        <willieej2002@y...> wrote:
        > Hello everyone. I am making a brand new language and I want it to
        > use constants similar to LB's.
        >
        > Is there some kind of command that will determine if the string is
        a
        > constant or will I have to define every single constant in windows?
        >
        > Help Please?
        >
        > ---
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