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provide better variable names in write_term_to_chars/3 (#340)

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This commit is contained in:
Mark Thom
2020-04-14 10:39:10 -06:00
parent db5ed345bc
commit 7799ed36f0
3 changed files with 72 additions and 57 deletions
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48
src/prolog/lib/charsio.pl
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@@ -3,6 +3,51 @@
:- use_module(library(iso_ext)).
fabricate_var_name(VarName, N) :-
char_code('A', AC),
LN is N mod 26 + AC,
char_code(LC, LN),
NN is N // 26,
( NN =:= 0 ->
atom_chars(VarName, ['_', LC])
; number_chars(NN, NNChars),
atom_chars(VarName, ['_', LC | NNChars])
).
var_list_contains_name([VarName = _ | VarList], VarName0) :-
( VarName == VarName0 -> true
; var_list_contains_name(VarList, VarName0)
).
var_list_contains_variable([_ = Var | VarList], Var0) :-
( Var == Var0 -> true
; var_list_contains_variable(VarList, Var0)
).
make_new_var_name(V, VarName, N, N1, VarList) :-
fabricate_var_name(VarName0, N),
( var_list_contains_name(VarList, VarName0) ->
N0 is N + 1,
make_new_var_name(V, VarName, N0, N1, VarList)
; VarName = VarName0,
N1 is N + 1
).
extend_var_list(Value, VarList, NewVarList) :-
term_variables(Value, Vars),
extend_var_list_(Vars, 0, VarList, NewVarList).
extend_var_list_([], N, VarList, VarList).
extend_var_list_([V|Vs], N, VarList, NewVarList) :-
( var_list_contains_variable(VarList, V) ->
extend_var_list_(Vs, N, VarList, NewVarList)
; make_new_var_name(V, VarName, N, N1, VarList),
NewVarList = [VarName = V | NewVarList0],
extend_var_list_(Vs, N1, VarList, NewVarList0)
).
read_term_from_chars(Chars, Term) :-
( var(Chars) ->
throw(error(instantiation_error, read_term_from_chars/2))
@@ -36,4 +81,5 @@ write_term_to_chars(Term, Options, Chars) :-
builtins:inst_member_or(Options, quoted(Quoted), quoted(false)),
builtins:inst_member_or(Options, variable_names(VarNames), variable_names([])),
builtins:inst_member_or(Options, max_depth(MaxDepth), max_depth(0)),
'$write_term_to_chars'(Term, IgnoreOps, NumberVars, Quoted, VarNames, MaxDepth, Chars).
extend_var_list(Term, VarNames, NewVarNames),
'$write_term_to_chars'(Term, IgnoreOps, NumberVars, Quoted, NewVarNames, MaxDepth, Chars).