git @ Cat's Eye Technologies Fountain / a27bae4
Crude pretty-printing is better than no pretty-printing. Chris Pressey 1 year, 5 months ago
3 changed file(s) with 36 addition(s) and 15 deletion(s). Raw diff Collapse all Expand all
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README.md less more
7676 ### Implementation
7777
7878 * Command-line option to start at a different goal symbol.
79 * Pretty-printer, so that the implementation tests can be more robust.
8079
8180 ### Documentation
8281
109108 "Both" combinator on constraints (which really needs reworking).
110109
111110 Implementation improvements such as better flattening of the AST
112 representing the grammar during its parsing.
111 representing the grammar during its parsing, and pretty-printing
112 fragments of the AST (albeit crudely) when displaying them.
113113
114114 ### 0.3
115115
+13
-11
doc/Tests-for-fountain.md less more
1717 Sequence.
1818
1919 Goal ::= "f" "o" "o";
20 ===> Grammar [("Goal",[],Alt [Seq [Terminal 'f',Terminal 'o',Terminal 'o']])]
20 ===> Goal ::= (("f" "o" "o"));
2121
2222 Multi-character terminals.
2323
2424 Goal ::= "foo" "bar";
25 ===> Grammar [("Goal",[],Alt [Seq [Terminal 'f',Terminal 'o',Terminal 'o',Terminal 'b',Terminal 'a',Terminal 'r']])]
25 ===> Goal ::= (("f" "o" "o" "b" "a" "r"));
2626
2727 Alternation and recursion.
2828
2929 Goal ::= "(" Goal ")" | "0";
30 ===> Grammar [("Goal",[],Alt [Seq [Terminal '(',NonTerminal "Goal" [],Terminal ')'],Seq [Terminal '0']])]
30 ===> Goal ::= (("(" Goal ")") | ("0"));
3131
3232 Repetition.
3333
3434 Goal ::= "(" {"0"} ")";
35 ===> Grammar [("Goal",[],Alt [Seq [Terminal '(',Loop (Alt [Seq [Terminal '0']]) [],Terminal ')']])]
35 ===> Goal ::= (("(" {(("0"))} ")"));
3636
3737 Constraints.
3838
4141 <. b = 0 .> { "b" <. b += 1 .> } <. b = n .>
4242 <. c = 0 .> { "c" <. c += 1 .> } <. c = n .>
4343 ;
44 ===> Grammar [("Goal",[],Alt [Seq [Constraint (UnifyConst (Var "a") 0),Loop (Alt [Seq [Terminal 'a',Constraint (Inc (Var "a") (CInt 1))]]) [],Constraint (UnifyVar (Var "a") (Var "n")),Constraint (UnifyConst (Var "b") 0),Loop (Alt [Seq [Terminal 'b',Constraint (Inc (Var "b") (CInt 1))]]) [],Constraint (UnifyVar (Var "b") (Var "n")),Constraint (UnifyConst (Var "c") 0),Loop (Alt [Seq [Terminal 'c',Constraint (Inc (Var "c") (CInt 1))]]) [],Constraint (UnifyVar (Var "c") (Var "n"))]])]
44 ===> Goal ::= ((<. a = 0 .> {(("a" <. a += 1 .>))} <. a = n .> <. b = 0 .> {(("b" <. b += 1 .>))} <. b = n .> <. c = 0 .> {(("c" <. c += 1 .>))} <. c = n .>));
4545
4646 Parameters and multiple productions.
4747
4848 Goal ::= "Hi" Sp<a> "there" Sp<b> "world" "!";
4949 Sp<n> ::= <. n = 0 .> { " " <. n += 1 .> } <. n > 0 .>;
50 ===> Grammar [("Goal",[],Alt [Seq [Terminal 'H',Terminal 'i',NonTerminal "Sp" [Var "a"],Terminal 't',Terminal 'h',Terminal 'e',Terminal 'r',Terminal 'e',NonTerminal "Sp" [Var "b"],Terminal 'w',Terminal 'o',Terminal 'r',Terminal 'l',Terminal 'd',Terminal '!']]),("Sp",[Var "n"],Alt [Seq [Constraint (UnifyConst (Var "n") 0),Loop (Alt [Seq [Terminal ' ',Constraint (Inc (Var "n") (CInt 1))]]) [],Constraint (GreaterThan (Var "n") (CInt 0))]])]
50 ===> Goal ::= (("H" "i" Sp<a> "t" "h" "e" "r" "e" Sp<b> "w" "o" "r" "l" "d" "!"));
51 ===> Sp<n> ::= ((<. n = 0 .> {((" " <. n += 1 .>))} <. n > 0 .>));
5152
5253 Comments.
5354
6162 //
6263 // There are many ways to place comments.
6364 "//";
64 ===> Grammar [("Goal",[],Alt [Seq [Terminal 'f',Terminal 'o',Terminal 'o']]),("A",[],Alt [Seq [Terminal 'f',Terminal 'o',Terminal '/',Terminal '/']])]
65 ===> Goal ::= (("f" "o" "o"));
66 ===> A ::= (("f" "o" "/" "/"));
6567
6668 Misplaced semicolon is a syntax error.
6769
7880 Sequence.
7981
8082 Goal ::= "f" "o" "o";
81 ===> Grammar [("Goal",[],Seq [Terminal 'f',Terminal 'o',Terminal 'o'])]
83 ===> Goal ::= ("f" "o" "o");
8284
8385 Alternation and recursion.
8486
8587 Goal ::= "(" Goal ")" | "0";
86 ===> Grammar [("Goal",[],Alt [Seq [Terminal '(',NonTerminal "Goal" [],Terminal ')'],Seq [Terminal '0']])]
88 ===> Goal ::= (("(" Goal ")") | ("0"));
8789
8890 Repetition.
8991
9092 Goal ::= "(" {"0"} ")";
91 ===> Grammar [("Goal",[],Seq [Terminal '(',Loop (Seq [Terminal '0']) [],Terminal ')'])]
93 ===> Goal ::= ("(" {("0")} ")");
9294
9395 Goal ::=
9496 <. a = 0 .> { "a" <. a += 1 .> } <. a = n .>
9597 <. b = 0 .> { "b" <. b += 1 .> } <. b = n .>
9698 <. c = 0 .> { "c" <. c += 1 .> } <. c = n .>
9799 ;
98 ===> Grammar [("Goal",[],Seq [Constraint (UnifyConst (Var "a") 0),Loop (Seq [Terminal 'a',Constraint (Inc (Var "a") (CInt 1))]) [UnifyVar (Var "a") (Var "n"),UnifyConst (Var "b") 0],Loop (Seq [Terminal 'b',Constraint (Inc (Var "b") (CInt 1))]) [UnifyVar (Var "b") (Var "n"),UnifyConst (Var "c") 0],Loop (Seq [Terminal 'c',Constraint (Inc (Var "c") (CInt 1))]) [UnifyVar (Var "c") (Var "n")]])]
100 ===> Goal ::= (<. a = 0 .> {("a" <. a += 1 .>)} {("b" <. b += 1 .>)} {("c" <. c += 1 .>)});
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src/Language/Fountain/Grammar.hs less more
00 module Language.Fountain.Grammar where
1
2 import Data.List (intercalate)
13
24 import Language.Fountain.Constraint
35
1517 | Terminal Char
1618 | NonTerminal NTName [Variable]
1719 | Constraint Constraint
18 deriving (Show, Ord, Eq)
20 deriving (Ord, Eq)
21
22 instance Show Expr where
23 show (Seq exprs) = "(" ++ (intercalate " " (map (show) exprs)) ++ ")"
24 show (Alt exprs) = "(" ++ (intercalate " | " (map (show) exprs)) ++ ")"
25 show (Loop expr _) = "{" ++ (show expr) ++ "}"
26 show (Terminal c) = "\"" ++ [c] ++ "\""
27 show (NonTerminal name vars) = name ++ showVars vars
28 show (Constraint c) = "<. " ++ (show c) ++ " .>"
29
30
31 showVars [] = ""
32 showVars vars = "<" ++ (intercalate ", " (map (show) vars)) ++ ">"
1933
2034
2135 data Grammar = Grammar [(NTName, [Variable], Expr)]
22 deriving (Show, Ord, Eq)
36 deriving (Ord, Eq)
37
38 instance Show Grammar where
39 show (Grammar []) = ""
40 show (Grammar ((name,vars,expr):rest)) = name ++ (showVars vars) ++ " ::= " ++ (show expr) ++ ";\n" ++ (show $ Grammar rest)
41
2342
2443 startSymbol (Grammar ((term, _, _) : _)) = term
2544 startSymbol (Grammar []) = error "No productions in grammar"