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defano / wyldcard

A clone of Apple's HyperCard and HyperTalk scripting language.
https://github.com/defano/wyldcard/wiki
MIT License
117 stars 12 forks source link

Put command "defaults" to *background* field (rather than "card") - how to change "priority"? Suggestions for ANTLR introduction book? #64

Closed Jimw338 closed 5 years ago

Jimw338 commented 5 years ago

I create a field, and then a button with the following mouseUp script:

on mouseDown ask "Enter a number" put it into field 1 --"output" end mouseDown

This complains that there is no background field. If I change it to card field, it works as I expect. Where in the code or grammar determines what the "default" specifier to use is?

What is recommended as a good "first ANTLR book"?

defano commented 5 years ago

Hi Jim,

The part of the grammar that defines this behavior is here:

fieldPart
    : card field 'id' term
    | background? field 'id' term
    | card field term
    | background? field term 
    | ordinal card field 
    | ordinal background? field
    | fieldPart of cardPart
    ;

... specifically, the background? field term rule. This causes the public Object visitBkgndFieldPart(HyperTalkParser.BkgndFieldPartContext ctx) method in the HyperTalkTreeVisitor class to fire, which, in turn, produces a PartNameExp node in the abstract syntax tree (which specifies a background field, not a card field).

I believe this behavior is consistent with HyperCard. button 1 refers to card button 1, but field 1 refers to background field 1. Go figure.

Unfortunately, I have no recommendations for any Antlr books. What little I know about the tool I learned through experimentation and Googling. :)