A Prolog-to-Python translator using list comprehensions

prolog_translator.jison

/* lexical grammar */
%lex
%%

\s+                   /* skip whitespace */
[0-9]+("."[0-9]+)?\b  return 'NUMBER'
\"([^\\\"]|\\.)*\" return 'STRING_LITERAL'
"forall"              return 'forall'
"copy_term"           return 'copy_term'
"if"                  return "if"
"is"                  return "is"
","                   return ','
";"                   return ';'
"--->"                return '--->'
"==>"                 return '==>'
"<=>"                 return '<=>'
"@"                   return '@'
"-->"                 return '-->'
"->"                  return '->'
":-"                  return ':-'
"."                   return '.'
":"                   return ':'
">="                  return '>='
">"                   return '>'
"=<"                  return '=<'
"<"                   return '<'
"=="                  return '=='
"="                   return '='
"*="                  return '*='
"*"                   return '*'
"\\="                 return '\\='
"/"                   return '/'
"-="                  return '-='
"--"                  return '--'
"-"                   return '-'
"++"                  return '++'
"+="                  return '+='
"+"                   return '+'
"^"                   return '^'
"{"                   return '{'
"}"                   return '}'
"|"                   return '|'
"["                   return '['
"]"                   return ']'
"("                   return '('
")"                   return ')'
[a-zA-Z_][a-zA-Z0-9_]* return 'IDENTIFIER'
<<EOF>>               return 'EOF'
.                     return 'INVALID'

/lex

/* operator associations and precedence */

%left '->'
%left ';'
%left ','
%left '<' '=<' '>' '>=' '=' '==' '\\=' 'is'
%left '+' '-'
%left '*' '/'
%left UMINUS

%start expressions

%% /* language grammar */

expressions: top_level_statements EOF {return $1};

top_level_statements: top_level_statement "." top_level_statements {$$ = $1+"\n"+$3;} | top_level_statement "." {$$ =
 $1;};
 
top_level_statement
    : IDENTIFIER "(" exprs ")" ":-" predicate_ {$$ = "def "+$1+"():\n    return [[" + $3.join()+"] for "+$6+"]"}
    | IDENTIFIER ":-" e {$$ = ["def " + $1 + "():",$3]};

predicate_: logic_and_ "," "(" e ")" {$$ = $1 +" if "+$3} | logic_and_;

logic_and_: function_call | logic_and_ "," function_call {$$ = $1 + " for " + $3};

e
    :
    e '->' e
        {$$ = ["(not("+$1+") or ("+$3+"))"]}
    |e ';' e
        {$$ = $1+ " or " +$3;}
    |e ',' e
        {$$ = $1+" and "+$3;}
    |e '=' e
        {$$ = $1+" == "+$3;}
    |e 'is' e
        {$$ = $1+"=="+$3;}
    |e '\\=' e
        {$$ = $1+"!="+$3;}
    |e '==' e
        {$$ = $1+"=="+$3;}
    |e '=<' e
        {$$ = $1+"<="+$3;}
    |e '<' e
        {$$ = $1+$2+$3;}
    | e '>=' e
        {$$ = $1+$2+$3;}
    |e '>' e
        {$$ = $1+$2+$3;}
    | e '+' e
        {$$ = $1+$2+$3;}
    | e '-' e
        {$$ = $1+$2+$3;}
    | e '*' e
        {$$ = $1+$2+$3;}
    | e '/' e
        {$$ = $1+$2+$3;}
    | '-' e %prec UMINUS
        {$$ = ["-",$2];}
    | not_expr
    ;

not_expr: "\+" parentheses_expr {$$ = "(not "+$2+")";} | parentheses_expr {$$ = $1;};

parameter: IDENTIFIER {$$ = $1;};
parameters: parameter "," parameters {$$ = $1+","+$3;} | parameter {$$ =
 $1;} | {$$ = ""};

function_call:
    IDENTIFIER "(" ")" {$$ = [$1+"()"];} | IDENTIFIER "(" exprs ")" {
		if($1 === "member"){
			$$ = $3.join(" in ");
		}
		else{
			$$ = ["["+$3.join(",")+"] in "+$1+"()"];
		}
	};

forall_statement: "forall" "(" e "," e ")" {$$ = ["forall",$3,$5];};

parentheses_expr:
    forall_statement
    | function_call
    | '(' e ')' {$$ = "("+$2+")";}
    | "[" "]" {$$ = "[]";}
    | "[" exprs "]" {$$ = "["+$2.join(",")+"]";}
    | "[" parentheses_expr "|" exprs "]" {$$ = "[" + $2 + "] + "+$4.join(",");}
    | NUMBER
        {$$ = yytext;}
    | IDENTIFIER
        {$$ = yytext;}
    | STRING_LITERAL
        {$$ = yytext;};

exprs: exprs "," parentheses_expr {$$ = $1.concat([$3]);} | parentheses_expr {$$ = [$1];};