As a static scope language, Jaskell supports dynamic scope with a few functions.
- define is the fundamental function that enables dynamic scope.
With define, one can place a java.util.Map or a tuple as the scope and all the members in the map or tuple are automatically visible to the following expression. For example:Though straight-forward, the above example isn't normally very useful. We could always use:Yet, define and its variants are more useful when the scope is dynamically determined. For example, the tuple or map can be provided by user at runtime. - with is a function derived from define. It is used to make visible all public methods and fields of an object to the following expression.
For example:is equivalent to the following java code:If you are familiar with the Basic language, this is essentially the "with" statement that allows us to invoke methods without explicitly writing down the object again and again. - do is another function derived from define. It is to mimic the monadic do notation where higher-order monadic combinators can be combined in an intuitive syntax. For example:
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