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Category:Fexl: Difference between revisions
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Fexl has no keywords, so whenever you see a symbol in a Fexl program, that symbol always refers to a function.
A symbol may be defined within a Fexl program, or its definition may be left entirely open. The definitions of all open symbols are supplied by a ''context''. A context is a function which supplies definitions for symbols. A context function
A Fexl program may therefore be resolved inside an arbitrary context, giving whatever meanings you like to all its open symbols. This makes it easy to wrap a Fexl program in an enhanced or restricted context. For example, in a web context you probably don't want "delete_file" to be defined at all, at least not in its normal sense. So you would you would resolve the program in a highly restricted context which only provides a handful of highly safe functions, omitting all the dangerous ones.
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