Build Problems Resolved

Mark S. Miller markm@caplet.com
Wed, 01 Sep 1999 12:19:11 -0700


At 09:14 AM 9/1/99 , mzukowski@bco.com wrote:
>What is a quasi-parser?

It is the parser component of a quasi-literal expression or quasi-literal
pattern, as explained by
http://www.erights.org/elang/grammar/quasi-overview.html  Briefly, there are
two forms of quasi-parser, a quasi-expression parser and a quasi-pattern
parser.

* A quasi-expression parser responds to 'valueMaker(String)' with a
ValueMaker derived from parsing the string while taking account of embedded
'${<number>}' holes.  A ValueMaker responds to 'substitute(List)' with an
object like that described by the original string, but with the elements
from the list substituted in for where the $-holes appeared in the description.

* A quasi-pattern parser responds to 'matchMaker(String)' with a MatchMaker
derived from parsing the string while taking account of embedded
'${<number>}' and '@{<number>}' holes.  A MatchMaker responds to
'matchBind(List, Object)' as if by first substituting in the elements of the
list into the $-holes, and then matching the object (the specimen) against
the pattern described by the original string as augmented by the
$-substitution.  If the match fails, 'matchBind' returns null.  If it
succeeds, it returns a list of values extracted by matching the specimen, in
which each extracted value corresponds to an @-hole.

>How is it different from a parser?

1) The input grammar is constrained to recognize $-holes and @-holes, since
the expansion of a quasi-literal will embed these without knowledge of the
syntax of the string that will be parsed.

2) The parser and its output must satisfy the one or both of the above two
protocols.

>In the generated code?

Huh?

> From whence this term quasi-parser, any references?

Originally from the "quasi-quote" of the lambda calculus.  I think Church
came up with quasi-quote well before Lisp.

>What could you accomplish with a quasi-parser that you can't with a parser?

Let me know if the previous answers have not adequately answered this.

>Are you really asking for an E language code generator?

Not in the same breath.  But sure, I'll ask ;)


         Cheers,
         --MarkM