I decide to create another thread about nondet. functions. The Mozart
support logic style of programming and this is very good. But it's luck
of library support this style! Any logic or functional-logic language
has predicate library for some that solves using logic propgramming
principes. For example, parsing text - typycal problem for logic
programming. I decide use 'choise' clause (in compliance with Peter Van
Roy's advice). But I meet with some difficults.
First, there are know comfortable way for unification strings by
pattern. For example, there no such function:
"1+1" = {AppendFull one sign two}
that bind variable one to '1', variable sign two '+' and variable two to
'1'.
Writing this function very easy and it's difficult to understand, why
it's not contained in Mozart libray:
proc {Append L1 L2 L3}
choice
L1 = nil L2 = L3
[] X T1 T3 in
L1 = X|T1 L3 = X|T3
{Append T1 L2 T3}
end
end
proc {AppendFull Lists List}
choice
Lists = nil List = nil
[] Y X|T = Lists in
{Append X Y List}
{AppendFull T Y}
end
end
Second, there is no nondet. functions for character analize. For
example, the functions in module Char is deterministik, e.g. function
isAlpha usable only in one direction:
{Char.isAlpha &a Result,}
but this is don't work:
{Char.isAlpha Ch true}.
Again, the realization of this functions is very easy and it's very
strange, that Mozart having so powerful realization of logic paradigm
luck of the library modules with set of nondeterministik functions.
PS Sorry for poor English, if some phrases don't understandable, I will
try to build them more correct.
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