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Implicit renaming macros
This module contains some macros to make the use of low-level implicit renaming macros easyier. Recall that those macros are implemented as a transformer routine, which is a three-parameter procedure
(lambda (form inject compare?) ...)
which has to be enclosed by an ir-macro-transformer call. The programmer's job is to destructure the macro-code, form. All symbols of the macro-expression not protected by inject are transparently renamed in the background to achieve hygiene. If no symbol is injected, the macro is automatically hygienic.
The job of destructuring the macro-code is tedious and error prone, it can be done by a tool, match from the matchable egg, for example. The other job, compare? literal symbols with those renamed behind the scene, something which is needed to use literals like else and => in the cond macro, remains to be done.
All macros in this module are unhygienic by design. They pollute the local (!) namespace with the symbols compare? and inject. But the macros implemented with those macros can be - and are in most cases - hygienic.
ir-macro-rules[syntax] (ir-macro-rules (sym ...) (pat0 xpr0) (pat1 xpr1) ...)
where each sym ... will break hygiene, hence the list (sym ...) is usually empty. pat0 pat1 ... are patterns describing admissible macro-codes (the macro-name can be replaced by an underscore) and xpr0 xpr1 ... are corresponding expressions which are evaluated to generate the macro expansion.
This macro is similar to and works like syntax-rules by design. That is, the macro-code is compared to pat0 pat1 in sequence and the expression paired to the first matching pattern is executed to generate the macro expansion. Nevertheless, there are two differences. First, the unrenamed symbols (sym ...) to be used in the expressions have nothing to do with literals like else and => in the cond macro (those must be handled by the unhygienic compare? symbol), and second, the patterns are not paired with templates as in syntax-rules, but with expressions which generate those templates (usually in the form of quasiquoted lists which contain the symbols sym ... unquoted). This makes ir-macro-rules much more flexible than syntax-rules: The programmer has the freedom to decide what to do at compile-time and what at runtime. The unhygienic injcet symbol is used if the macro exports new unrenamed (!) symbols.
macro-rules[syntax] (macro-rules (sym ...) (pat0 xpr0) (pat1 xpr1) ...)
Alias of ir-macro-rules.
ir-macro-define[syntax] (ir-macro-define (name . args) . body)
defines a macro with macro-code (name . args) by means of body, which is either a sequence of expressions xpr . xprs which generate a template, or a list of the form (with (sym ...) xpr . xprs). In the latter case the macro is unhygienic and pollutes its local namespace with sym ..., in the former case it is hygienic.
Note, that this macro in its hygienic form has exactly the same syntax as define-macro of Chicken-3 and other Schemes!
macro-define[syntax] (macro-define (name . args) . body)
Alias of ir-macro-define
ir-macro-let[syntax] (ir-macro-let ((code0 . body0) ...) . body)
where code0 ... is the macro-code (name0 . args0) ... of a local macro and body0 ... the corresponding body which generates a template. As in ir-macro-define this must either be a sequence of expressions, xpr0 . xprs0, or a list of the form (with (sym0 ...) xpr0 . xprs0). In the latter case the local macros are unhygienic. These macros are locally defined in parallel and in there scope body is executed.
macro-let[syntax] (macro-let ((code0 body0) ...) . body)
Alias of ir-macro-let
ir-macro-letrec[syntax] (ir-macro-letrec ((code0 body0) ...) . body)
recursive version of ir-macro-let, i.e. the local macros have access to each other.
macro-letrec[syntax] (macro-letrec ((code0 body0) ...) . body)
Alias of ir-macro-letrec
(import ir-macros) (import-for-syntax (only matchable match) (only ir-macros macro-rules ir-macro-rules))
(define-syntax my-or (ir-macro-rules () ((_) #f) ((_ arg . args) `(if ,arg ,arg (my-or ,@args)))))
Copyright (c) 2011, Juergen Lorenz All rights reserved.
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- All macros in this egg made unhygienic by design
- changed syntax of [ir-]macro-rules, thanks to Moritz Heidkamp
- added additional inject argument to all transformers
- initial import