1:- module(onepointfour_basics_stringy_morph, 2 [ 3 stringy_morph/4 % stringy_morph(StringyA,StringyB,TypeA,TypeB) 4 ,stringy_morph/5 % stringy_morph(StringyA,StringyB,TypeA,TypeB,Tuned) 5 ,stringy_charylist_morph/4 % stringy_charylist_morph(Stringy,Charylist,StringyType,CharylistType) 6 ,stringy_charylist_morph/5 % stringy_charylist_morph(Stringy,Charylist,StringyType,CharylistType,Tuned) 7 ]). 8 9:- use_module(library('onepointfour_basics/checks.pl')). 10:- use_module(library('onepointfour_basics/stringy_and_charylist_type.pl')). 11 12/* MIT License Follows (https://opensource.org/licenses/MIT) 13 14 Copyright 2021 David Tonhofer <ronerycoder@gluino.name> 15 16 Permission is hereby granted, free of charge, to any person obtaining 17 a copy of this software and associated documentation files 18 (the "Software"), to deal in the Software without restriction, 19 including without limitation the rights to use, copy, modify, merge, 20 publish, distribute, sublicense, and/or sell copies of the Software, 21 and to permit persons to whom the Software is furnished to do so, 22 subject to the following conditions: 23 24 The above copyright notice and this permission notice shall be 25 included in all copies or substantial portions of the Software. 26 27 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 28 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 29 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 30 IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 31 CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, 32 TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE 33 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 34*/ 35 36/* pldoc ==================================================================== */

A replacement for atom_string/2

This code is specific to SWI-Prolog, as that Prolog provides the traditional "atom" and the non-traditional "string" as two distinct representations of "sequences of characters".

We introduce the following additional vocabulary:

A stringy term is a term that is either an atom or a string. In SWI-Prolog, the string is a distinct representation of a sequence of characters, distinct from the atom and mean to be used in text processing rather than as basis for identifiers.
A chary term is a term that is either a char (an atom of length 1) or a code (an integer and, more precisely in SWI-Prolog, a Unicode code point).
A charylist is less precise: it is a proper list of either codes or chars. It may or may not contain uninstantiated elements. An empty list is a charylist but we cannot know whether it is supposed to be composed of codes or chars. A list containing only uninstantiated variables is also a charylist and again we don't know what it is supposed to contain, at least not yet.

Homepage for this code

https://github.com/dtonhofer/prolog_code/blob/main/unpacked/onepointfour_basics/README_stringy_morph.md

History

2021-01-19: Reviewed
2021-02-16: Reviewed for packs, updated to pldoc.
2021-02-17: Trashed all the old code for testing "stringyness" and wrote new one based on the "texty type tree"
2021-06-11: Back up on github */

98stringy_morph(StringyA,StringyB,TypeA,TypeB,Tuned) :- 99 check_that([StringyA,StringyB],[hard(passany(nonvar))]), 100 check_that(StringyA, [break(var),tuned(stringy)],Tuned), 101 check_that(StringyB, [break(var),tuned(stringy)],Tuned), 102 check_that(TypeA, [break(var),tuned(stringy_typeid)],Tuned), 103 check_that(TypeB, [break(var),tuned(stringy_typeid)],Tuned), 104 stringy_type(StringyA,AsGivenTypeA), 105 stringy_type(StringyB,AsGivenTypeB), 106 stringy_morph_2_with_increased_determinism(AsGivenTypeA,AsGivenTypeB,StringyA,StringyB,TypeA,TypeB). 107 108% stringy_morph_2(AsGivenTypeA,AsGivenTypeB,StringyA,StringyB,TypeA,TypeB). 109% 110% The case AsGivenTypeA=var,AsGiventypeB=var is precluded by a check in 111% stringy_morph/5 112% 113% Note that even if the types correspond, we must still check whether 114% the text representations correspond. 115 116stringy_morph_2_with_increased_determinism(AsGivenTypeA,AsGivenTypeB,StringyA,StringyB,TypeA,TypeB) :- 117 ( 118 (AsGivenTypeA==var,nonvar(TypeA)); 119 (AsGivenTypeB==var,nonvar(TypeB)) 120 ), 121 !, 122 stringy_morph_2(AsGivenTypeA,AsGivenTypeB,StringyA,StringyB,TypeA,TypeB), % we know there is only 1 solution 123 !. 124stringy_morph_2_with_increased_determinism(AsGivenTypeA,AsGivenTypeB,StringyA,StringyB,TypeA,TypeB) :- 125 stringy_morph_2(AsGivenTypeA,AsGivenTypeB,StringyA,StringyB,TypeA,TypeB). 126 127% stringy_morph_2(AsGivenTypeA,AsGivenTypeB,StringyA,StringyB,TypeA,TypeB). 128% ------------ | nonvar on call | | can be var on call | 129 130stringy_morph_2( string, string , A , B , string, string ) :- A=B. 131stringy_morph_2( string, atom , A , B , string, atom ) :- atom_string(B,A). 132stringy_morph_2( string, var , A , B , string, string ) :- A=B. 133stringy_morph_2( string, var , A , B , string, atom ) :- atom_string(B,A). 134 135stringy_morph_2( atom, string , A , B , atom , string ) :- atom_string(A,B). 136stringy_morph_2( atom, atom , A , B , atom , atom ) :- A=B. 137stringy_morph_2( atom, var , A , B , atom , string ) :- atom_string(A,B). 138stringy_morph_2( atom, var , A , B , atom , atom ) :- A=B. 139 140stringy_morph_2( var, atom , A , B , string, atom ) :- atom_string(B,A). 141stringy_morph_2( var, atom , A , B , atom , atom ) :- A=B. 142stringy_morph_2( var, string , A , B , string, string ) :- A=B. 143stringy_morph_2( var, string , A , B , atom , string ) :- atom_string(A,B).

154stringy_charylist_morph(Stringy,Charylist,StatedStringyType,StatedCharylistType,Tuned) :- 155 check_that(Stringy, [break(var),tuned(stringy)],Tuned), 156 check_that(StatedStringyType, [break(var),tuned(stringy_typeid)],Tuned), 157 check_that(StatedCharylistType, [break(var),tuned(member(char,code,chars,codes))],Tuned), 158 fix(StatedCharylistType,StatedCharylistType2), 159 % Won't fail because Stringy is well-typed after check_that/2 160 stringy_type_with_length(Stringy,ActualStringyType), 161 % May fail as Charylist may be ill-typed 162 (charylist_type(Charylist,ActualCharylistType) 163 -> 164 true 165 ; 166 check_that(Charylist,[fail("Charylist has unrecognized type")],Tuned)), 167 (\+underspecified(ActualStringyType,ActualCharylistType) 168 -> 169 true 170 ; 171 check_that([Stringy,Charylist],[fail("Stringy-Charylist combination underspecifies")],Tuned)), 172 (compatible_cross_combinations(ActualStringyType,ActualCharylistType) 173 -> 174 true 175 ; 176 check_that([ActualStringyType,ActualCharylistType],[fail("Stringy-Charylist type combination incompatible")],Tuned)), 177 % below here it's gettign interesting; the cur is really not needed 178 % fails on bad combination or may generate other solutions on redo 179 enumerate_compatible_stringy_type_with_increased_determinism(ActualStringyType,StatedStringyType), 180 % fails on bad combination or may generate other solutions on redo 181 enumerate_compatible_charylist_type_with_increased_determinism(ActualCharylistType,StatedCharylistType2), 182 % we make the exercise of explicitly calling the correct builtin depending on case 183 ((ActualStringyType==var) 184 -> 185 % morph nonvar "Charylist" to a stringy according to "StringyType" and unify 186 % with "Stringy", possibly yielding two solutions (atoms,strings) 187 morph_from_charylist_with_increased_determinism(StatedCharylistType2,StatedStringyType,Charylist,Stringy) 188 ; 189 % morph nonvar "Stringy" to a charylist according to "StatedCharylistType2" and 190 % unify with "Charylist", possibly yielding two solutions (codes,chars) 191 morph_from_stringy_with_increased_determinism(StatedStringyType,StatedCharylistType2,Stringy,Charylist)). 192 193 194% fix(StatedCharylistType,Fixed) 195% The caller may have passed any of char,chars,code,codes; unify! 196 197fix(X,X) :- var(X),!. 198fix(chars,chars) :- !. 199fix(char,chars) :- !. 200fix(codes,codes) :- !. 201fix(code,codes). 202 203% enumerate_compatible_stringy_type(ActualStringyType,StatedStringyType) 204% 205% This is an implementation of this table, where incompatible 206% combinations have been left out and thus fail 207% 208% ActualStringyType StatedStringyType (may be var) 209% ------------------------------ 210% 'var' Var,'atom','string' StringyType can be bound to 'atom' or 'string' 211% 'atom(L)' Var,'atom' StringyType must be bound to 'atom' 212% 'string(L)' Var,'string' StringyType must be bound to 'string' 213% 214 215enumerate_compatible_stringy_type_with_increased_determinism(A,B) :- 216 assertion(nonvar(A)), 217 nonvar(B), 218 !, 219 enumerate_compatible_stringy_type(A,B), 220 !. 221enumerate_compatible_stringy_type_with_increased_determinism(A,B) :- 222 enumerate_compatible_stringy_type(A,B). 223 224enumerate_compatible_stringy_type(string(_),string). 225enumerate_compatible_stringy_type(atom(_),atom). 226enumerate_compatible_stringy_type(var,atom). 227enumerate_compatible_stringy_type(var,string). 228 229% enumerate_compatible_charylist_type(ActualCharylistType,StatedCharylistType) 230 231enumerate_compatible_charylist_type_with_increased_determinism(A,B) :- 232 assertion(nonvar(A)), 233 nonvar(B), 234 !, 235 enumerate_compatible_charylist_type(A,B), 236 !. 237enumerate_compatible_charylist_type_with_increased_determinism(A,B) :- 238 enumerate_compatible_charylist_type(A,B). 239 240enumerate_compatible_charylist_type(chars(_),chars). 241enumerate_compatible_charylist_type(codes(_),codes). 242enumerate_compatible_charylist_type(chars_vars(_,_),chars). 243enumerate_compatible_charylist_type(codes_vars(_,_),codes). 244enumerate_compatible_charylist_type(empty,chars). 245enumerate_compatible_charylist_type(empty,codes). 246enumerate_compatible_charylist_type(vars(_),chars). 247enumerate_compatible_charylist_type(vars(_),codes). 248enumerate_compatible_charylist_type(var,chars). 249enumerate_compatible_charylist_type(var,codes). 250 251% underspecified(ActualStringyType,ActualCharysType) 252% 253% List the type combinations which leave too much leeway for a meaningful answer. 254 255underspecified(var,var). 256underspecified(var,vars(_)). 257underspecified(var,chars_vars(_,_)). 258underspecified(var,codes_vars(_,_)). 259 260% compatible_cross_combinations(ActualStringyType,ActualCharysType) 261% 262% List the type combinations for which Stringy<->Charys morph makes sense. 263 264compatible_cross_combinations(string(L),chars(L)). 265compatible_cross_combinations(string(L),codes(L)). 266compatible_cross_combinations(atom(L),chars(L)). 267compatible_cross_combinations(atom(L),codes(L)). 268compatible_cross_combinations(string(L),chars_vars(C,V)) :- L =:= C+V. 269compatible_cross_combinations(string(L),codes_vars(C,V)) :- L =:= C+V. 270compatible_cross_combinations(atom(L),chars_vars(C,V)) :- L =:= C+V. 271compatible_cross_combinations(atom(L),codes_vars(C,V)) :- L =:= C+V. 272compatible_cross_combinations(string(0),empty). 273compatible_cross_combinations(atom(0),empty). 274compatible_cross_combinations(string(L),vars(L)). 275compatible_cross_combinations(atom(L),vars(L)). 276compatible_cross_combinations(string(_),var). 277compatible_cross_combinations(atom(_),var). 278 279compatible_cross_combinations(var,chars(_)). 280compatible_cross_combinations(var,codes(_)). 281compatible_cross_combinations(var,empty). 282 283% morph_from_stringy(StringyType,CharylistType,StringyIn,CharylistOut) 284% More complex than need to get determinism on the first two arguments 285 286morph_from_stringy_with_increased_determinism(A,B,C,D) :- 287 assertion(nonvar(A)), 288 nonvar(B), 289 !, 290 morph_from_stringy(A,B,C,D), 291 !. 292morph_from_stringy_with_increased_determinism(A,B,C,D) :- 293 morph_from_stringy(A,B,C,D). 294 295morph_from_stringy(string , chars , StringyIn , CharylistOut) :- string_chars(StringyIn,CharylistOut). 296morph_from_stringy(string , codes , StringyIn , CharylistOut) :- string_codes(StringyIn,CharylistOut). 297morph_from_stringy(atom , chars , StringyIn , CharylistOut) :- atom_chars(StringyIn,CharylistOut). 298morph_from_stringy(atom , codes , StringyIn , CharylistOut) :- atom_codes(StringyIn,CharylistOut). 299 300% morph_from_charylist(CharylistType,StringyType,CharylistIn,StringyOut) 301 302morph_from_charylist_with_increased_determinism(A,B,C,D) :- 303 assertion(nonvar(A)), 304 nonvar(B), 305 !, 306 morph_from_charylist(A,B,C,D), 307 !. 308morph_from_charylist_with_increased_determinism(A,B,C,D) :- 309 morph_from_charylist(A,B,C,D). 310 311morph_from_charylist(chars , string , CharylistIn, StringyOut) :- string_chars(StringyOut,CharylistIn). 312morph_from_charylist(chars , atom , CharylistIn, StringyOut) :- atom_chars(StringyOut,CharylistIn). 313morph_from_charylist(codes , string , CharylistIn, StringyOut) :- string_codes(StringyOut,CharylistIn). 314morph_from_charylist(codes , atom , CharylistIn, StringyOut) :- atom_codes(StringyOut,CharylistIn). 315morph_from_charylist(empty , string , [], ""). 316morph_from_charylist(empty , atom , [], '')