#4372: Extending quasiquotation support
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Reporter: simonpj | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Template Haskell | Version: 6.12.3
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Comment(by gershomb):
This is all shorthand, you're right. But the syntactic sugar makes a huge
difference here. In quasiquote syntax, the only quotation issue that an
end user has to worry about is the bar followed by close bracket. In
standard splice syntax, the quoted expression is forced to respect all the
rules of haskell. Multiline strings either use the \ syntax are have to be
written with explicit appends. Double quotes need additional escaping,
etc. Furthermore, error messages can't give nearly as nice locality.
With quasiquotes, its possible to write very fluently in an embedded dsl
with almost arbitrary concrete syntax. Template Haskell splices on their
own make doing so very painful.
Most of the libraries using quasiquotation that I now know of would be
extremely painful to use without the shorthand syntax provided by
quasiquotation.
In general, Kathleen's preference is fine -- super lightweight syntax for
the simple case, and extended syntax for the extended case. This causes a
bit more work at the lexing level, and in the parser (but only a few
lines), but subsequent to that there's a single code path which is as
simple as or simpler than what exists now.
In fact, '[$' for introducing an extended quoter and '|' alone for
introducing the quotee, which is what I've now implemented, seems fine to
me as well, unless there is strong sentiment otherwise.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4372#comment:9>
GHC <http://www.haskell.org/ghc/>
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