Scopes

As explained in Definitions, min uses lexical scoping to resolve symbols and sigils. A scope is an execution context (a symbol table really) that:

• is created while a new quotation is being dequoted or a dictionary is created.
• is destroyed after a quotation has been dequoted.
• is attached to a dictionary.

The main, root-level scope in min can be accessed using the global Module symbol and it typically contains all symbols and sigils imported from all the standard library modules. The global symbol pushes a module on the stack that references the global scope:

Accessing the current scope

You can access the current scope using the scope operator, which pushes a module on the stack that references the current scope.

Consider the following program:

In this case:

1. A new variable called innerscope is defined on the global scope.
2. A quotation is dequoted, but its scope is retrieved using the scope operator and bound to innerscope.
3. After the quotation is dequoted, myscope is accessed and its symbols (test in this case) are pushed on the stack using the scope-symbols operator.

Note that scopes can only be accessed if they are bound to a dictionary, hence the global and scope operators push a module on the stack, and a module is nothing but a typed dictionary.

Dequoting a quotation within the context of a specific scope

The with operator can be used to dequote a quotation within a specific scope instead of the current one.

Consider the following program, which leaves 2 on the stack:

In this case, when with is pushed on the stack, it will dequote (4 2 minus). Note that the symbol minus is defined in the dictionary that will be used by with as the current scope, so after with is pushed on the stack, the stack contents are:

At this point, the dequote operator is pushed on the stack and the subtraction is executed leaving 2 on the stack.

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