From Newsgroup: comp.lang.lisp

[ Repost from Reddit. r/lisp: https://t.ly/Fldzk ]

Hello everyone.

I am making a Scheme R5RS implementation and it is going pretty well.

I am trying implement macros, and don't really know how to implement them. Scheme has a pretty complex macro system, so for now I am trying to
implement defmacro and then implement define-syntax, syntax-case, etc.

Any tips?

Thanks in advance.
--
- mario
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From Newsgroup: comp.lang.lisp

Mario Rosell <mario@mariorosell.es> writes:

[ Repost from Reddit. r/lisp: https://t.ly/Fldzk ]

Hello everyone.

I am making a Scheme R5RS implementation and it is going pretty well.

I am trying implement macros, and don't really know how to implement them. Scheme has a pretty complex macro system, so for now I am trying to
implement defmacro and then implement define-syntax, syntax-case, etc.

Any tips?

using eval is your friend.


the old emacs way was hard to read.

the emacs lisp info page: "

14.1 A Simple Example of a Macro
================================

Suppose we would like to define a Lisp construct to increment a variable
value, much like the rCy++rCO operator in C. We would like to write rCy(inc x)rCO and have the effect of rCy(setq x (1+ x))rCO. Here's a macro definition that does the job:

(defmacro inc (var)
(list 'setq var (list '1+ var)))

"

you need to ``reevaluate'' the macro twice.

the commmon lisp was uses symbols like @ , . etc..


hope this is helpful.
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From Newsgroup: comp.lang.lisp

On Tue, 16 Jun 2026 21:50:26 -0400, steve g wrote:

the old emacs way was hard to read.

the commmon lisp was uses symbols like @ , . etc..

ThatrCOs the traditional way of doing it, also supported by Emacs
(naturally).
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From Newsgroup: comp.lang.lisp

steve g <Sgonedes1977@gmail.com> writes:

you need to ``reevaluate'' the macro twice.
the commmon lisp was uses symbols like @ , . etc..

That's been built into Emacs Lisp for quite a while too. Before it was
built into the reader, it was available as a loadable macro package so
you'd write something like (` (setq (, var) (1+ (, var))) . Now it's
like CL, `(setq ,var (1+ ,var)) .
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From Newsgroup: comp.lang.lisp

Mario Rosell <mario@mariorosell.es> wrote:

[ Repost from Reddit. r/lisp: https://t.ly/Fldzk ]

Hello everyone.

I am making a Scheme R5RS implementation and it is going pretty well.

I am trying implement macros, and don't really know how to implement them. Scheme has a pretty complex macro system, so for now I am trying to
implement defmacro and then implement define-syntax, syntax-case, etc.

Any tips?

Naive macros are easy: when you see macro definition you handle
it almost as a function, except for that you mark resulting
object as a macro. In evaluator (or in compiler if you have one)
you first check if the form is a macro call (that is head is marked as
a macro), if it is than you execute corresponding macro function applying
it to unevaluated arguments. When macro function returns you
handle result as new source code.

Once you have naive macros you can add niceties like quasiquote
by preprocessing the macro definition. In other words, better
macro can be implemented as macro definition which processes
its argument and then passes it to naive macro.

I am not familiar with details of Scheme macros, but it is quite
likely that they could be implemented in similar way on top of
naive macros.
--
Waldek Hebisch
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From Newsgroup: comp.lang.lisp

Paul Rubin <no.email@nospam.invalid> writes:

steve g <Sgonedes1977@gmail.com> writes:

you need to ``reevaluate'' the macro twice.
the commmon lisp was uses symbols like @ , . etc..

That's been built into Emacs Lisp for quite a while too. Before it was
built into the reader, it was available as a loadable macro package so
you'd write something like (` (setq (, var) (1+ (, var))) . Now it's
like CL, `(setq ,var (1+ ,var)) .

yes, I do remeber this. very compilcated to read; much better now.
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From Newsgroup: comp.lang.lisp

On 2026-06-12, Mario Rosell <mario@mariorosell.es> wrote:

[ Repost from Reddit. r/lisp: https://t.ly/Fldzk ]

Hello everyone.

I am making a Scheme R5RS implementation and it is going pretty well.

I am trying implement macros, and don't really know how to implement them. Scheme has a pretty complex macro system, so for now I am trying to
implement defmacro and then implement define-syntax, syntax-case, etc.

Any tips?

There exists more than one algorithm for hygienic macros.

The "grand daddy" is Kohlbecker's algorithm (1986)

The offshoots:

- Syntactic closures (1988)
- Alan Bawden paper from the proceedings of the 1988 ACM conference on Lisp
and functional programming.
- Chris Hanson 1991 paper, "A Syntactic Closure Macro Facility".

- Modified Kohlbecker's algorithm:
- William Clinger's 1990 paper, "Macros That Work"
- claims to address issues with syntactic closures
- reduces Kohlbecker from quadratic to linear time
--
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal
Mastodon: @Kazinator@mstdn.ca
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From Newsgroup: comp.lang.lisp

There exists more than one algorithm for hygienic macros.

The "grand daddy" is Kohlbecker's algorithm (1986)

The offshoots:

- Syntactic closures (1988)
- Alan Bawden paper from the proceedings of the 1988 ACM conference on Lisp
and functional programming.
- Chris Hanson 1991 paper, "A Syntactic Closure Macro Facility".

- Modified Kohlbecker's algorithm:
- William Clinger's 1990 paper, "Macros That Work"
- claims to address issues with syntactic closures
- reduces Kohlbecker from quadratic to linear time

Might be worth mentioning the "sets of scopes" one used in Racket:

Binding as sets of scopes
Matthew Flatt. POPL 2016.
doi: 10.1145/2837614.2837620


=== Stefan
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