Trying to use mutually recursive values don't compile, giving the error:
syntax error: replacing AND with UNDER
Parse failure
----------
Here is a sample to try with:
val rec even (i:int) = if i = 0 then True
else if i > 0 then odd (i -1)
else error <xml>error: negative input</xml>
and val rec odd (i:int) = if i = 0 then False
else if i > 0 then even (i -1)
else error <xml>error: negative input</xml>
(* --- *)
I have found the syntax problem in urweb.grm in the non-terminal
production "valis" used in declarations (decl production) and local
declarations (edecl production).
decl :...
| VAL REC valis
| FUN valis
vali : SYMBOL eargl2 copt EQ eexp
valis : vali ([vali])
| vali AND valis (vali :: valis)
----------
A simple working patch:
valis : vali ([vali])
| vali AND VAL REC valis (vali :: valis)
| vali AND FUN valis (vali :: valis)
But it is recommended to avoid right recursion in LR grammars because of
rightmost derivation [1], so another tested proposal is
valis : vali ([vali])
| valis AND VAL REC vali (valis @ [vali])
| valis AND FUN vali (valis @ [vali])
-------------
[1] Lex-YACC-HOWTO - 6.2 Recursion: 'right is wrong'
(http://tldp.org/HOWTO/Lex-YACC-HOWTO-6.html#ss6.2)
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