1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448
|
\chapter{ML Functions in the Library}\label{entries}\input{entries-intro}\DOC{DELETE\_CONV}
\TYPE {\small\verb%DELETE_CONV : conv -> conv%}\egroup
\SYNOPSIS
Reduce {\small\verb%{x1,...,xn} DELETE x%} by deleting {\small\verb%x%} from {\small\verb%{x1,...,xn}%}.
\DESCRIBE
The function {\small\verb%DELETE_CONV%} is a parameterized conversion for reducing finite
sets of the form {\small\verb%"{t1,...,tn} DELETE t"%}, where {\small\verb%{t1,...,tn}%} is a set of
type {\small\verb%(ty)set%} and {\small\verb%t%} is a term of type {\small\verb%ty%}. The first argument to
{\small\verb%DELETE_CONV%} is expected to be a conversion that decides equality between
values of the base type {\small\verb%ty%}. Given an equation {\small\verb%"e1 = e2"%}, where {\small\verb%e1%} and
{\small\verb%e2%} are terms of type {\small\verb%ty%}, this conversion should return the theorem
{\small\verb%|- (e1 = e2) = T%} or the theorem {\small\verb%|- (e1 = e2) = F%}, as appropriate.
Given such a conversion {\small\verb%conv%}, the function {\small\verb%DELETE_CONV%} returns a
conversion that maps a term of the form {\small\verb%"{t1,...,tn} DELETE t"%} to the
theorem
{\par\samepage\setseps\small
\begin{verbatim}
|- {t1,...,tn} DELETE t = {ti,...,tj}
\end{verbatim}
}
\noindent where {\small\verb%{ti,...,tj}%} is the subset of {\small\verb%{t1,...,tn}%} for which
the supplied equality conversion {\small\verb%conv%} proves
{\par\samepage\setseps\small
\begin{verbatim}
|- (ti = t) = F, ..., |- (tj = t) = F
\end{verbatim}
}
\noindent and for all the elements {\small\verb%tk%} in {\small\verb%{t1,...,tn}%} but not in
{\small\verb%{ti,...,tj}%}, either {\small\verb%conv%} proves {\small\verb%|- (tk = t) = T%} or {\small\verb%tk%} is
alpha-equivalent to {\small\verb%t%}. That is, the reduced set {\small\verb%{ti,...,tj}%} comprises
all those elements of the original set that are provably not equal to the
deleted element {\small\verb%t%}.
\EXAMPLE
In the following example, the conversion {\small\verb%num_EQ_CONV%} is supplied as a
parameter and used to test equality of the deleted value {\small\verb%2%} with the
elements of the set.
{\par\samepage\setseps\small
\begin{verbatim}
#DELETE_CONV num_EQ_CONV "{2,1,SUC 1,3} DELETE 2";;
|- {2,1,SUC 1,3} DELETE 2 = {1,3}
\end{verbatim}
}
\FAILURE
{\small\verb%DELETE_CONV conv%} fails if applied to a term not of the form {\small\verb%"{t1,...,tn}
DELETE t"%}. A call {\small\verb%DELETE_CONV conv "{t1,...,tn} DELETE t"%} fails unless
for each element {\small\verb%ti%} of the set {\small\verb%{t1,...,tn}%}, the term {\small\verb%t%} is either
alpha-equivalent to {\small\verb%ti%} or {\small\verb%conv "ti = t"%} returns {\small\verb%|- (ti = t) = T%} or
{\small\verb%|- (ti = t) = F%}.
\SEEALSO
INSERT_CONV.
\ENDDOC
\DOC{IMAGE\_CONV}
\TYPE {\small\verb%IMAGE_CONV : conv -> conv -> conv%}\egroup
\SYNOPSIS
Compute the image of a function on a finite set.
\DESCRIBE
The function {\small\verb%IMAGE_CONV%} is a parameterized conversion for computing the image
of a function {\small\verb%f:ty1->ty2%} on a finite set {\small\verb%"{t1,...,tn}"%} of type
{\small\verb%(ty1)set%}. The first argument to {\small\verb%IMAGE_CONV%} is expected to be a conversion
that computes the result of applying the function {\small\verb%f%} to each element of this
set. When applied to a term {\small\verb%"f ti"%}, this conversion should return a theorem
of the form {\small\verb%|- (f ti) = ri%}, where {\small\verb%ri%} is the result of applying the function
{\small\verb%f%} to the element {\small\verb%ti%}. This conversion is used by {\small\verb%IMAGE_CONV%} to compute a
theorem of the form
{\par\samepage\setseps\small
\begin{verbatim}
|- IMAGE f {t1,...,tn} = {r1,...,rn}
\end{verbatim}
}
\noindent The second argument to {\small\verb%IMAGE_CONV%} is used (optionally) to simplify
the resulting image set {\small\verb%{r1,...,rn}%} by removing redundant occurrences of
values. This conversion expected to decide equality of values of the result
type {\small\verb%ty2%}; given an equation {\small\verb%"e1 = e2"%}, where {\small\verb%e1%} and {\small\verb%e2%} are terms of
type {\small\verb%ty2%}, the conversion should return either {\small\verb%|- (e1 = e2) = T%} or
{\small\verb%|- (e1 = e2) = F%}, as appropriate.
Given appropriate conversions {\small\verb%conv1%} and {\small\verb%conv2%}, the function {\small\verb%IMAGE_CONV%}
returns a conversion that maps a term of the form {\small\verb%"IMAGE f {t1,...,tn}"%} to
the theorem
{\par\samepage\setseps\small
\begin{verbatim}
|- IMAGE f {t1,...,tn} = {rj,...,rk}
\end{verbatim}
}
\noindent where {\small\verb%conv1%} proves a theorem of the form {\small\verb%|- (f ti) = ri%} for each
element {\small\verb%ti%} of the set {\small\verb%{t1,...,tn}%}, and where the set {\small\verb%{rj,...,rk}%} is
the smallest subset of {\small\verb%{r1,...,rn}%} such no two elements are
alpha-equivalent and {\small\verb%conv2%} does not map {\small\verb%"rl = rm"%} to the theorem
{\small\verb%|- (rl = rm) = T%} for any pair of values {\small\verb%rl%} and {\small\verb%rm%} in {\small\verb%{rj,...,rk}%}.
That is, {\small\verb%{rj,...,rk}%} is the set obtained by removing multiple occurrences
of values from the set {\small\verb%{r1,...,rn}%}, where the equality conversion {\small\verb%conv2%}
(or alpha-equivalence) is used to determine which pairs of terms in
{\small\verb%{r1,...,rn}%} are equal.
\EXAMPLE
The following is a very simple example in which {\small\verb%REFL%} is used to construct the
result of applying the function {\small\verb%f%} to each element of the set {\small\verb%{1,2,1,4}%},
and {\small\verb%NO_CONV%} is the supplied `equality conversion'.
{\par\samepage\setseps\small
\begin{verbatim}
#IMAGE_CONV REFL NO_CONV "IMAGE (f:num->num) {1,2,1,4}";;
|- IMAGE f{1,2,1,4} = {f 2,f 1,f 4}
\end{verbatim}
}
\noindent The result contains only one occurrence of `{\small\verb%f 1%}', even though
{\small\verb%NO_CONV%} always fails, since {\small\verb%IMAGE_CONV%} simplifies the resulting set by
removing elements that are redundant up to alpha-equivalence.
For the next example, we construct a conversion that maps {\small\verb%SUC n%} for any
numeral {\small\verb%n%} to the numeral standing for the successor of {\small\verb%n%}.
{\par\samepage\setseps\small
\begin{verbatim}
#let SUC_CONV tm =
let n = int_of_string(fst(dest_const(rand tm))) in
let sucn = mk_const(string_of_int(n+1), ":num") in
SYM (num_CONV sucn);;
SUC_CONV = - : conv
\end{verbatim}
}
\noindent The result is a conversion that inverts {\small\verb%num_CONV%}:
{\par\samepage\setseps\small
\begin{verbatim}
#num_CONV "4";;
|- 4 = SUC 3
#SUC_CONV "SUC 3";;
|- SUC 3 = 4
\end{verbatim}
}
\noindent The conversion {\small\verb%SUC_CONV%} can then be used to compute the image
of the successor function on a finite set:
{\par\samepage\setseps\small
\begin{verbatim}
#IMAGE_CONV SUC_CONV NO_CONV "IMAGE SUC {1,2,1,4}";;
|- IMAGE SUC{1,2,1,4} = {3,2,5}
\end{verbatim}
}
\noindent Note that {\small\verb%2%} (= {\small\verb%SUC 1%}) appears only once in the resulting set.
Fianlly, here is an example of using {\small\verb%IMAGE_CONV%} to compute the image of a
paired addition function on a set of pairs of numbers:
{\par\samepage\setseps\small
\begin{verbatim}
#IMAGE_CONV (PAIRED_BETA_CONV THENC ADD_CONV) num_EQ_CONV
"IMAGE (\(n,m).n+m) {(1,2), (3,4), (0,3), (1,3)}";;
|- IMAGE(\(n,m). n + m){(1,2),(3,4),(0,3),(1,3)} = {7,3,4}
\end{verbatim}
}
\FAILURE
{\small\verb%IMAGE_CONV conv1 conv2%} fails if applied to a term not of the form
{\small\verb%"IMAGE f {t1,...,tn}"%}. An application of {\small\verb%IMAGE_CONV conv1 conv2%} to
a term {\small\verb%"IMAGE f {t1,...,tn}"%} fails unless for all {\small\verb%ti%} in the set
{\small\verb%{t1,...,tn}%}, evaluating {\small\verb%conv1 "f ti"%} returns {\small\verb%|- (f ti) = ri%}
for some {\small\verb%ri%}.
\ENDDOC
\DOC{IN\_CONV}
\TYPE {\small\verb%IN_CONV : conv -> conv%}\egroup
\SYNOPSIS
Decision procedure for membership in finite sets.
\DESCRIBE
The function {\small\verb%IN_CONV%} is a parameterized conversion for proving or disproving
membership assertions of the general form:
{\par\samepage\setseps\small
\begin{verbatim}
"t IN {t1,...,tn}"
\end{verbatim}
}
\noindent where {\small\verb%{t1,...,tn}%} is a set of type {\small\verb%(ty)set%} and {\small\verb%t%} is a value
of the base type {\small\verb%ty%}. The first argument to {\small\verb%IN_CONV%} is expected to be a
conversion that decides equality between values of the base type {\small\verb%ty%}. Given
an equation {\small\verb%"e1 = e2"%}, where {\small\verb%e1%} and {\small\verb%e2%} are terms of type {\small\verb%ty%}, this
conversion should return the theorem {\small\verb%|- (e1 = e2) = T%} or the theorem
{\small\verb%|- (e1 = e2) = F%}, as appropriate.
Given such a conversion, the function {\small\verb%IN_CONV%} returns a conversion that
maps a term of the form {\small\verb%"t IN {t1,...,tn}"%} to the theorem
{\par\samepage\setseps\small
\begin{verbatim}
|- t IN {t1,...,tn} = T
\end{verbatim}
}
\noindent if {\small\verb%t%} is alpha-equivalent to any {\small\verb%ti%}, or if the supplied conversion
proves {\small\verb%|- (t = ti) = T%} for any {\small\verb%ti%}. If the supplied conversion proves
{\small\verb%|- (t = ti) = F%} for every {\small\verb%ti%}, then the result is the theorem
{\par\samepage\setseps\small
\begin{verbatim}
|- t IN {t1,...,tn} = F
\end{verbatim}
}
\noindent In all other cases, {\small\verb%IN_CONV%} will fail.
\EXAMPLE
In the following example, the conversion {\small\verb%num_EQ_CONV%} is supplied as a
parameter and used to test equality of the candidate element {\small\verb%1%} with the
actual elements of the given set.
{\par\samepage\setseps\small
\begin{verbatim}
#IN_CONV num_EQ_CONV "2 IN {0,SUC 1,3}";;
|- 2 IN {0,SUC 1,3} = T
\end{verbatim}
}
\noindent The result is {\small\verb%T%} because {\small\verb%num_EQ_CONV%} is able to prove that {\small\verb%2%} is
equal to {\small\verb%SUC 1%}. An example of a negative result is:
{\par\samepage\setseps\small
\begin{verbatim}
#IN_CONV num_EQ_CONV "1 IN {0,2,3}";;
|- 1 IN {0,2,3} = F
\end{verbatim}
}
\noindent Finally the behaviour of the supplied conversion is irrelevant when
the value to be tested for membership is alpha-equivalent to an actual element:
{\par\samepage\setseps\small
\begin{verbatim}
#IN_CONV NO_CONV "1 IN {3,2,1}";;
|- 1 IN {3,2,1} = T
\end{verbatim}
}
\noindent The conversion {\small\verb%NO_CONV%} always fails, but {\small\verb%IN_CONV%} is nontheless
able in this case to prove the required result.
\FAILURE
{\small\verb%IN_CONV conv%} fails if applied to a term that is not of the form {\small\verb%"t IN
{t1,...,tn}"%}. A call {\small\verb%IN_CONV conv "t IN {t1,...,tn}"%} fails unless the
term {\small\verb%t%} is alpha-equivalent to some {\small\verb%ti%}, or {\small\verb%conv "t = ti"%} returns
{\small\verb%|- (t = ti) = T%} for some {\small\verb%ti%}, or {\small\verb%conv "t = ti"%} returns
{\small\verb%|- (t = ti) = F%} for every {\small\verb%ti%}.
\ENDDOC
\DOC{INSERT\_CONV}
\TYPE {\small\verb%INSERT_CONV : conv -> conv%}\egroup
\SYNOPSIS
Reduce {\small\verb%x INSERT {x1,...,x,...,xn}%} to {\small\verb%{x1,...,x,...,xn}%}.
\DESCRIBE
The function {\small\verb%INSERT_CONV%} is a parameterized conversion for reducing finite
sets of the form {\small\verb%"t INSERT {t1,...,tn}"%}, where {\small\verb%{t1,...,tn}%} is a set of
type {\small\verb%(ty)set%} and {\small\verb%t%} is equal to some element {\small\verb%ti%} of this set. The first
argument to {\small\verb%INSERT_CONV%} is expected to be a conversion that decides equality
between values of the base type {\small\verb%ty%}. Given an equation {\small\verb%"e1 = e2"%}, where
{\small\verb%e1%} and {\small\verb%e2%} are terms of type {\small\verb%ty%}, this conversion should return the theorem
{\small\verb%|- (e1 = e2) = T%} or the theorem {\small\verb%|- (e1 = e2) = F%}, as appropriate.
Given such a conversion, the function {\small\verb%INSERT_CONV%} returns a conversion that
maps a term of the form {\small\verb%"t INSERT {t1,...,tn}"%} to the theorem
{\par\samepage\setseps\small
\begin{verbatim}
|- t INSERT {t1,...,tn} = {t1,...,tn}
\end{verbatim}
}
\noindent if {\small\verb%t%} is alpha-equivalent to any {\small\verb%ti%} in the set {\small\verb%{t1,...,tn}%}, or
if the supplied conversion proves {\small\verb%|- (t = ti) = T%} for any {\small\verb%ti%}.
\EXAMPLE
In the following example, the conversion {\small\verb%num_EQ_CONV%} is supplied as a
parameter and used to test equality of the inserted value {\small\verb%2%} with the
remaining elements of the set.
{\par\samepage\setseps\small
\begin{verbatim}
#INSERT_CONV num_EQ_CONV "2 INSERT {1,SUC 1,3}";;
|- {2,1,SUC 1,3} = {1,SUC 1,3}
\end{verbatim}
}
\noindent In this example, the supplied conversion {\small\verb%num_EQ_CONV%} is able to
prove that {\small\verb%2%} is equal to {\small\verb%SUC 1%} and the set is therefore reduced. Note
that {\small\verb%"2 INSERT {1,SUC 1,3}"%} is just {\small\verb%"{2,1,SUC 1,3}"%}.
A call to {\small\verb%INSERT_CONV%} fails when the value being inserted is provably not
equal to any of the remaining elements:
{\par\samepage\setseps\small
\begin{verbatim}
#INSERT_CONV num_EQ_CONV "1 INSERT {2,3}";;
evaluation failed INSERT_CONV
\end{verbatim}
}
\noindent But this failure can, if desired, be caught using {\small\verb%TRY_CONV%}.
The behaviour of the supplied conversion is irrelevant when the inserted value
is alpha-equivalent to one of the remaining elements:
{\par\samepage\setseps\small
\begin{verbatim}
#INSERT_CONV NO_CONV "(y:*) INSERT {x,y,z}";;
|- {y,x,y,z} = {x,y,z}
\end{verbatim}
}
\noindent The conversion {\small\verb%NO_CONV%} always fails, but {\small\verb%INSERT_CONV%} is
nontheless able in this case to prove the required result.
Note that {\small\verb%DEPTH_CONV(INSERT_CONV conv)%} can be used to remove duplicate
elements from a finite set, but the following conversion is faster:
{\par\samepage\setseps\small
\begin{verbatim}
#letrec REDUCE_CONV conv tm =
(SUB_CONV (REDUCE_CONV conv) THENC (TRY_CONV (INSERT_CONV conv))) tm;;
REDUCE_CONV = - : (conv -> conv)
#REDUCE_CONV num_EQ_CONV "{1,2,1,3,2,4,3,5,6}";;
|- {1,2,1,3,2,4,3,5,6} = {1,2,4,3,5,6}
\end{verbatim}
}
\FAILURE
{\small\verb%INSERT_CONV conv%} fails if applied to a term not of the form
{\small\verb%"t INSERT {t1,...,tn}"%}. A call {\small\verb%INSERT_CONV conv "t INSERT {t1,...,tn}"%}
fails unless {\small\verb%t%} is alpha-equivalent to some {\small\verb%ti%}, or {\small\verb%conv "t = ti"%} returns
{\small\verb%|- (t = ti) = T%} for some {\small\verb%ti%}.
\SEEALSO
DELETE_CONV.
\ENDDOC
\DOC{SET\_INDUCT\_TAC}
\TYPE {\small\verb%SET_INDUCT_TAC : tactic%}\egroup
\SYNOPSIS
Tactic for induction on finite sets.
\DESCRIBE
{\small\verb%SET_INDUCT_TAC%} is an induction tacic for proving properties of finite
sets. When applied to a goal of the form
{\par\samepage\setseps\small
\begin{verbatim}
!s:(*)set. P[s]
\end{verbatim}
}
\noindent {\small\verb%SET_INDUCT_TAC%} reduces this goal to proving that the property
{\small\verb%\s.P[s]%} holds of the empty set and is preserved by insertion of an element
into an arbitrary finite set. Since every finite set can be built up from the
empty set {\small\verb%"{}"%} by repeated insertion of values, these subgoals imply that
the property {\small\verb%\s.P[s]%} holds of all finite sets.
The tactic specification of {\small\verb%SET_INDUCT_TAC%} is:
{\par\samepage\setseps\small
\begin{verbatim}
A ?- !s.P
================================================== SET_INDUCT_TAC
A |- P[{}/s]
A u {P[s'/s], ~e IN s'} ?- P[e INSERT s'/s]
\end{verbatim}
}
\noindent where {\small\verb%e%} is a variable chosen so as not to appear free in the
assumptions {\small\verb%A%}, and {\small\verb%s'%} is a primed variant of {\small\verb%s%} that does not appear free
in {\small\verb%A%} (usually, {\small\verb%s'%} is just {\small\verb%s%}).
\FAILURE
{\small\verb%SET_INDUCT_TAC (A,g)%} fails unless {\small\verb%g%} has the form {\small\verb%!s.P%}, where the variable
{\small\verb%s%} has type {\small\verb%(ty)set%} for some type {\small\verb%ty%}.
\ENDDOC
\DOC{UNION\_CONV}
\TYPE {\small\verb%UNION_CONV : conv -> conv%}\egroup
\SYNOPSIS
Reduce {\small\verb%{t1,...,tn} UNION s%} to {\small\verb%t1 INSERT (... (tn INSERT s))%}.
\DESCRIBE
The function {\small\verb%UNION_CONV%} is a parameterized conversion for reducing sets of
the form {\small\verb%"{t1,...,tn} UNION s"%}, where {\small\verb%{t1,...,tn}%} and {\small\verb%s%} are sets of
type {\small\verb%(ty)set%}. The first argument to {\small\verb%UNION_CONV%} is expected to be a
conversion that decides equality between values of the base type {\small\verb%ty%}. Given
an equation {\small\verb%"e1 = e2"%}, where {\small\verb%e1%} and {\small\verb%e2%} are terms of type {\small\verb%ty%}, this
conversion should return the theorem {\small\verb%|- (e1 = e2) = T%} or the theorem
{\small\verb%|- (e1 = e2) = F%}, as appropriate.
Given such a conversion, the function {\small\verb%UNION_CONV%} returns a conversion that
maps a term of the form {\small\verb%"{t1,...,tn} UNION s"%} to the theorem
{\par\samepage\setseps\small
\begin{verbatim}
|- t UNION {t1,...,tn} = ti INSERT ... (tj INSERT s)
\end{verbatim}
}
\noindent where {\small\verb%{ti,...,tj}%} is the set of all terms {\small\verb%t%} that occur as
elements of {\small\verb%{t1,...,tn}%} for which the conversion {\small\verb%IN_CONV conv%} fails to
prove that {\small\verb%|- (t IN s) = T%} (that is, either by proving {\small\verb%|- (t IN s) = F%}
instead, or by failing outright).
\EXAMPLE
In the following example, {\small\verb%num_EQ_CONV%} is supplied as a parameter to
{\small\verb%UNION_CONV%} and used to test for membership of each element of the first
finite set {\small\verb%{1,2,3}%} of the union in the second finite set {\small\verb%{SUC 0,3,4}%}.
{\par\samepage\setseps\small
\begin{verbatim}
#UNION_CONV num_EQ_CONV "{1,2,3} UNION {SUC 0,3,4}";;
|- {1,2,3} UNION {SUC 0,3,4} = {2,SUC 0,3,4}
\end{verbatim}
}
\noindent The result is {\small\verb%{2,SUC 0,3,4}%}, rather than {\small\verb%{1,2,SUC 0,3,4}%},
because {\small\verb%UNION_CONV%} is able by means of a call to
{\par\samepage\setseps\small
\begin{verbatim}
IN_CONV num_EQ_CONV "1 IN {SUC 0,3,4}"
\end{verbatim}
}
\noindent to prove that {\small\verb%1%} is already an element of the set {\small\verb%{SUC 0,3,4}%}.
The conversion supplied to {\small\verb%UNION_CONV%} need not actually prove equality of
elements, if simplification of the resulting set is not desired. For example:
{\par\samepage\setseps\small
\begin{verbatim}
#UNION_CONV NO_CONV "{1,2,3} UNION {SUC 0,3,4}";;
|- {1,2,3} UNION {SUC 0,3,4} = {1,2,SUC 0,3,4}
\end{verbatim}
}
\noindent In this case, the resulting set is just left unsimplified. Moreover,
the second set argument to {\small\verb%UNION%} need not be a finite set:
{\par\samepage\setseps\small
\begin{verbatim}
#UNION_CONV NO_CONV "{1,2,3} UNION s";;
|- {1,2,3} UNION s = 1 INSERT (2 INSERT (3 INSERT s))
\end{verbatim}
}
\noindent And, of course, in this case the conversion argument to {\small\verb%UNION_CONV%}
is irrelevant.
\FAILURE
{\small\verb%UNION_CONV conv%} fails if applied to a term not of the form
{\small\verb%"{t1,...,tn} UNION s"%}.
\SEEALSO
IN_CONV.
\ENDDOC
|