One random little feature of GNAT that comes in handy for me is its

habit of, when I misspell an identifier, giving me a possible correction

in its compile error message.  Spending some time with the 3.10.0

sources, I have created a "second draft" patch creating this

functionality in my favored language.

Example:

========

# /home/thelema/Projects/ocaml-custom/bin/ocamlc -o coml -I +lablgtk2

lablgtk.cma gtkInit.cmo coml.ml

File "coml.ml", line 61, characters 16-25:

Unbound value is_arcive, possible misspelling of is_archive

Impacts:

========

Efficiency in the case of finding a mistake should be quite good,

although this shouldn't matter too much since the compiler quits pretty

early in compilation when it finds an unbound identifier.

In the case of no unbound identifiers, the cost is an extra try/with

block around the standard lookup.  I haven't made any benchmarks, though.

I expect this code to have little long term maintenance issues - the

major source of code changes was adding a "* string list" to a number of

exceptions to carry the list of possible correct spellings to the point

they get output by the compiler.  These exceptions are still usable as

before with an empty list in this spot.

It's possible the code has created opportunities for uncaught exceptions

in the compiler as I only checked for instances of "Not_found" in a few

files -- those which dealt with the Unbound_* exceptions.  Someone who

knows the internals better might find places the "Found_nearly"

exception that carries possible corrections might escape into.

Dedicated to:

Yaron Minsky and the team at Jane Street

E.