[m-dev.] Infix syntax proposal
Douglas Michael Auclair
dauclair at hotmail.com
Wed Aug 14 21:43:24 AEST 2002
I propose the following amendment to the infix syntax -- add a declaration
to the language of the form:
:- infix foo, bar, baz.
This declaration allows the above binary functions (foo, bar, and baz) to be
used in the following way (e.g.):
X foo Y, 3 bar 7, "Quux" baz 42.
It transforms the above into:
X `foo` Y, 3 `bar` 7, "Quuz" `baz` 42.
Working a good deal with the pprint module has made Doc1 `<>` Doc2 both
tedious and alien. I also define quite a few binary functions and would
like them to be on equal footing with the builtins at the source level when
I plan to use them as infix functions.
I have attached a toy program that transforms files with infix declarations
(let's call the file foo.infix) to .m files. It is used thus:
./infix < foo.infix > foo.m
I propose that this infix transformer, if accepted, become part of the
(m)make process, so that the first source transformation resolves infix
calls and is transparent to users of mmake/mmc.
1. Very little to compilation time: running infix over large programs is not
noticeable. There is one more IR that must be passed around either in
memory or as a (temporary) file.
2. No syntactic/semantic _cost_: old modules compile as before, and, even
with an infix declaration, one may still use the back-quote convention or
the prefix style -- a smart infix pass will not disturb these pre-existing
constructs (even the attached "toy" program works well with these
3. New-style infix modules will not compile under the old system without
first being transformed.
4. Increased opportunities for compile-time errors: the user must remember
to declare target binary functions as infix, otherwise the compiler will
report an error at or near the infix call.
1. User-defined and declared infix calls are treated as equals to builtin
binary functions at the source level.
I have used this proposed infix syntax and the transforming program on two
projects so far. The new syntax seems more natural to use and to review
than the back-quote convention.
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