Assignment-2/parser.y

%{

#include <string>
#include <iostream>
#include <set>
#include "parser.hpp"

%}

%token INDENT
%token DEDENT
%token NEWLINE
%token AND
%token BREAK
%token DEF
%token ELIF
%token ELSE
%token FOR
%token IF
%token NOT
%token OR
%token RETURN
%token WHILE
%token BOOLEAN
%token FLOAT
%token INTEGER
%token IDENTIFIER
%token ASSIGN
%token PLUS
%token MINUS
%token TIMES
%token DIVIDEDBY
%token EQ
%token NEQ
%token GT
%token GTE
%token LT
%token LTE
%token LPAREN
%token RPAREN
%token COMMA
%token COLON

%define api.value.type { std::string* }
%define api.pure full
%define api.push-pull push
%start program

%{

template <typename T, typename std::enable_if<std::is_convertible<T, const char*>::value, T>::type* = nullptr>
void concat(std::string* s, T vs) {
    s->append(vs);
}

template <typename T, typename std::enable_if<std::is_convertible<T, std::string*>::value, T>::type* = nullptr>
void concat(std::string* s, T vs) {
    s->append(*vs);
    delete vs;
}

template <typename T, typename ... Ts>
void concat(std::string* s, T v, Ts ... vs) {
    concat(s, v);
    concat(s, vs...);
}

template <typename ... Ts>
std::string* concatenate(Ts ... vs) {
    std::string* temp = new std::string();
    concat(temp, vs...);
    return temp;
}

void yyerror(const char* s) {
    std::cout << s << std::endl;
}

std::set<std::string> varset;

%}

%%

program
    : stmts { std::cout << *$1 << std::endl; $$ = $1; }
    ;

stmts
    : stmts stmt { $$ = concatenate($1, $2); }
    | stmt { $$ = $1; }
    ;

stmt
    : expr NEWLINE { $$ = concatenate($1, ";"); }
    | if { $$ = $1; }
    | while { $$ = $1; }
    | BREAK NEWLINE { $$ = new std::string("break;"); }
    ;

expr
    : assign { $$ = $1; }
    | eq { $$ = $1; }
    ;

while
    : WHILE expr COLON NEWLINE block { $$ = concatenate("while(", $2, ")", $5); }
    ;

if
    : IF expr COLON NEWLINE block elses { $$ = concatenate("if(", $2, ")", $5, $6); }
    ;

elses
    : %empty { $$ = new std::string(""); }
    | elif elses { $$ = concatenate($1, $2); }
    | else { $$ = $1; }
    ;

elif
    : ELIF expr COLON NEWLINE block { $$ = concatenate("else if(", $2, ")", $5); }
    ;

else
    : ELSE COLON NEWLINE block { $$ = concatenate("else", $4); }
    ;

block
    : INDENT stmts DEDENT { $$ = concatenate("{", $2, "}"); }
    ;

assign
    : IDENTIFIER ASSIGN expr { varset.insert(*$1); $$ = concatenate($1, "=", $3); }
    ;

eq
    : eq EQ rel { $$ = concatenate($1, "==", $3); }
    | eq NEQ rel { $$ = concatenate($1, "!=", $3); }
    | rel { $$ = $1; }
    ;

rel
    : rel LT sum { $$ = concatenate($1, "<", $3); }
    | rel LTE sum { $$ = concatenate($1, "<=", $3); }
    | rel GT sum { $$ = concatenate($1, ">", $3); }
    | rel GTE sum { $$ = concatenate($1, ">=", $3); }
    | sum { $$ = $1; }
    ;

sum
    : sum PLUS factor { $$ = concatenate($1, "+", $3); }
    | sum MINUS factor { $$ = concatenate($1, "-", $3); }
    | factor { $$ = $1; }
    ;

factor
    : factor TIMES term { $$ = concatenate($1, "*", $3); }
    | factor DIVIDEDBY term { $$ = concatenate($1, "/", $3); }
    | term { $$ = $1; }
    ;

term
    : IDENTIFIER { $$ = $1; }
    | FLOAT { $$ = $1; }
    | INTEGER { $$ = $1; }
    | BOOLEAN { $$ = $1; }
    | LPAREN expr RPAREN { $$ = $2; }
    ;

%%