NEW: Files for testing Prolog parser / demonstrating legal and illegal Prolog syntax.

Author: Guenter Kniesel

PDT Examples/CTeditorTests/atoms-numbers-strings.pl

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+
+/* 
+   Testcases of all syntax variations.
+   Everything that does not require cross-file scoping.
+*/
+
+%============== Facts with all kinds of terms as parameters ==========
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% Integers and decimal numbers:
+a(0).    % integer
+a(1.0).  % decimal number
+a(1,0).  % two arguments!
+
+% 2.15.1.5 Using digit groups in large integers
+% 
+% SWI-Prolog supports splitting long integers into digit groups.
+% Digit groups can be separated with the sequence <underscore>, 
+% <optional white space>. If the <radix> is 10 or lower, they 
+% may also be separated with exactly one space. 
+% http://www.swi-prolog.org/pldoc/man?section=digitgroupsyntax
+% The following all express the integer 1 million:
+
+a(1_000_000).
+a(1 000 000).
+a(1_000_/*more*/000).
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% 2.15.1.4 Syntax for non-decimal numbers
+% Edinburgh syntax:
+%   <radix>'<number>, where <radix> is a number between 2 and 36. 
+% ISO syntax: 
+%   0[bxo]<number>. For example: A is 0b100 \/ 0xf00 is a valid expression.  
+% http://www.swi-prolog.org/pldoc/man?section=nondecsyntax
+
+a(2'1010). % Edinburgh: binary representation of 10
+a(8'12).   % Edinburgh: octal representation of 10
+a(16'A).   % Edinburgh: hexadecimal representation of 10
+
+%a(1'1).    % Edinburgh: Illegal, radix must be above 1
+% <-- Syntax error: Operator expected (is not the most helpful
+% <-- message but at least it is an error message
+%a(37'1).   % Edinburgh: Illegal, radix must be below 37
+% <-- Throws no error at this point but many lines below it will
+% <-- say: Syntax error: String too long (see style_check/1)
+ 
+a(0b1010). % ISO: binary representation of 10
+a(0o12).   % ISO: octal representation of 10
+a(0xA).    % ISO: hexadecimal representation of 10
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% 2.15.1.2 Nested comments
+/* 
+   SWI-Prolog allows for nesting /* ... */ comments like this one 
+*/
+% http://www.swi-prolog.org/pldoc/man?section=nestedcomments
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% 2.15.1.3 Character Escape Syntax
+% Within quoted atoms special characters are represented using escape 
+% sequences. An escape sequence is led in by the backslash (\) character.
+% Character escaping is only available if 
+% current_prolog_flag(character_escapes, true) is active (default). 
+% http://www.swi-prolog.org/pldoc/man?section=charescapes
+
+a('abc-\a\b\c\
+\e\f\n\r\s\t\v-def').
+% The code \xa\3 emits the character 10 (hexadecimal `a') followed by `3'. 
+% Characters specified this way are interpreted as Unicode characters. See also \u.
+a('abc-\xa\3-def'). 
+a('abc-\u1111-def').
+%a('abc-\U11111111-def').  % Legal unicode sign in the Hangul character set
+%a('\U11111111').          % Legal unicode sign in the Hangul character set
+a('\40').
+a('\\').
+a('\"').
+a('\'').
+a('\`').

PDT Examples/CTeditorTests/function_terms.pl

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+
+a(f).
+a(f()).                 % Illegal before SWI-Prolog 7.x
+a(f(1)).
+a(f(_)).
+a(f(X,X,Y,Y,1,2,3,4)).
+a('blub'(1)).
+a(_blub(1)).            % Illegal
+
+a([]).
+a([1,2,3]).
+a([1|[2,3]]).
+a([1|2,3]).             % Illegal
+
+

PDT Examples/CTeditorTests/quotes.pl

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+% Demonstrate the effect of \c:
+
+:- module( quotes_demo,
+         [ a/1
+         ] ).
+
+
+a(atom__(X)) :-
+	X = 'alpha
+		bravo
+		charlie'.
+
+a(atom_c(X)) :-
+    X = 'alpha
+		bravo  \c
+		charlie'.
+
+a(string__(X)) :- 
+	X = "alpha
+		bravo 
+		charlie".
+		
+a(string_c(X)) :- 
+	X = "alpha
+		bravo \c
+		charlie".
+

PDT Examples/CTeditorTests/singletons.pl

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+/*
+2.15.1.9 Singleton variable checking
+
+A singleton variable is a variable that appears only one time in a 
+clause. It can always be replaced by _, the anonymous variable. 
+
+In some cases, however, people prefer to give the variable a name. 
+As mistyping a variable is a common mistake, Prolog systems generally 
+give a warning (controlled by style_check/1) if a variable is used 
+only once. 
+The system can be informed that a variable is meant to appear once by 
+starting it with an underscore, e.g., _Name. 
+Please note that any variable, except plain _, shares with variables 
+of the same name. The term t(_X, _X) is equivalent to t(X, X), which 
+is different from t(_, _). 
+% http://www.swi-prolog.org/pldoc/man?section=singleton
+*/
+test(_).    
+test(_a).	% Singleton variables: [_a]
+test(_12).	% Singleton variables: [_12]
+test(A).	% Singleton variables: [A]
+test(_A).
+test(__a).
+test(_, _).
+test(_a, _a).
+test(__a, __a).	% Singleton-marked variables appearing more than once: [__a]
+test(_A, _A).	% Singleton-marked variables appearing more than once: [_A]
+test(A, A). 
+
+/*
+Semantic singletons
+
+Starting with version 6.5.1, SWI-Prolog has syntactic singletons and 
+semantic singletons. The first are checked by read_clause/3 (and 
+read_term/3 using the option singletons(warning)). 
+
+The latter are generated by the compiler for variables that appear 
+alone in a branch. For example, in the code below the variable X is 
+not a syntactic singleton, but the variable X does not communicate any 
+bindings and replacing X with _ does not change the semantics.
+*/
+
+test :-
+        (   test_1(X)
+        ;   test_2(X)
+        ).