Reference: PLT Scheme

1`` | Language Model
2`` | Syntactic Forms
3`` | Datatypes
4`` | Structures
5`` | Classes and Objects
6`` | Units
7`` | Contracts
8`` | Pattern Matching
9`` | Control Flow
10`` | Concurrency
11`` | Macros
12`` | Input and Output
13`` | Reflection and Security
14`` | Operating System
15`` | Memory Management
16`` | Running PLT Scheme
| Bibliography
| Index

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#%top

Version: 4.0.2
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#### 2.5`` Variable References and #%top

id

Refers to a module-level or local binding, when id is not bound as a transformer (see Expansion). At run-time, the reference evaluates to the value in the location associated with the binding.

When the expander encounters an id that is not bound by a module-level or local binding, it converts the expression to (#%top . id) giving #%top the lexical context of the id; typically, that context refers to #%top. See also Expansion Steps.

Examples:
> (define x 10)
> x
10
> (let ([x 5]) x)
5
> ((lambda (x) x) 2)
2

(#%top . id)

Refers to a top-level definition that could bind id, even if id has a local binding in its context. Such references are disallowed anywhere within a module form. See also Expansion Steps for information on how the expander introduces #%top identifiers.

Examples:
> (define x 12)
> (let ([x 5]) (#%top . x))
12

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