Move code into folders for convenience

01/scanner.l

@@ -0,0 +1,33 @@
+%option noyywrap
+
+%{
+#include <iostream>
+%}
+
+%%
+
+[ \n]+ {}
+\+ { std::cout << "PLUS" << std::endl; }
+\* { std::cout << "TIMES" << std::endl; }
+- { std::cout << "MINUS" << std::endl; }
+\/ { std::cout << "DIVIDE" << std::endl; }
+[0-9]+ { std::cout << "NUMBER: " << yytext << std::endl; }
+defn { std::cout << "KEYWORD: defn" << std::endl; }
+data { std::cout << "KEYWORD: data" << std::endl; }
+case { std::cout << "KEYWORD: case" << std::endl; }
+of { std::cout << "KEYWORD: of" << std::endl; }
+\{ { std::cout << "OPEN CURLY" << std::endl; }
+\} { std::cout << "CLOSED CURLY" << std::endl; }
+\( { std::cout << "OPEN PARENTH" << std::endl; }
+\) { std::cout << "CLOSE PARENTH" << std::endl; }
+,  { std::cout << "COMMA" << std::endl; }
+-> { std::cout << "PATTERN ARROW" << std::endl; }
+= { std::cout << "EQUAL" << std::endl; }
+[a-z][a-zA-Z]* { std::cout << "LOWERCASE IDENTIFIER: " << yytext << std::endl; }
+[A-Z][a-zA-Z]* { std::cout << "UPPERCASE IDENTIFIER: " << yytext << std::endl; }
+
+%%
+
+int main() {
+    yylex();
+}

02/ast.hpp

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+#pragma once
+#include <memory>
+#include <vector>
+
+struct ast {
+    virtual ~ast() = default;
+};
+
+using ast_ptr = std::unique_ptr<ast>;
+
+struct pattern {
+    virtual ~pattern() = default;
+};
+
+using pattern_ptr = std::unique_ptr<pattern>;
+
+struct branch {
+    pattern_ptr pat;
+    ast_ptr expr;
+
+    branch(pattern_ptr p, ast_ptr a)
+        : pat(std::move(p)), expr(std::move(a)) {}
+};
+
+using branch_ptr = std::unique_ptr<branch>;
+
+struct definition {
+    virtual ~definition() = default;
+};
+
+using definition_ptr = std::unique_ptr<definition>;
+
+enum binop {
+    PLUS,
+    MINUS,
+    TIMES,
+    DIVIDE
+};
+
+struct ast_int : public ast {
+    int value;
+
+    explicit ast_int(int v)
+        : value(v) {}
+};
+
+struct ast_lid : public ast {
+    std::string id;
+
+    explicit ast_lid(std::string i)
+        : id(std::move(i)) {}
+};
+
+struct ast_uid : public ast {
+    std::string id;
+
+    explicit ast_uid(std::string i)
+        : id(std::move(i)) {}
+};
+
+struct ast_binop : public ast {
+    binop op;  
+    ast_ptr left;
+    ast_ptr right;
+
+    ast_binop(binop o, ast_ptr l, ast_ptr r)
+        : op(o), left(std::move(l)), right(std::move(r)) {}
+};
+
+struct ast_app : public ast {
+    ast_ptr left;
+    ast_ptr right;
+
+    ast_app(ast_ptr l, ast_ptr r)
+        : left(std::move(l)), right(std::move(r)) {}
+};
+
+struct ast_case : public ast {
+    ast_ptr of;
+    std::vector<branch_ptr> branches;
+
+    ast_case(ast_ptr o, std::vector<branch_ptr> b)
+        : of(std::move(o)), branches(std::move(b)) {}
+};
+
+struct pattern_var : public pattern {
+    std::string var;
+
+    pattern_var(std::string v)
+        : var(std::move(v)) {}
+};
+
+struct pattern_constr : public pattern {
+    std::string constr;
+    std::vector<std::string> params;
+
+    pattern_constr(std::string c, std::vector<std::string> p)
+        : constr(std::move(c)), params(std::move(p)) {}
+};
+
+struct definition_defn : public definition {
+    std::string name;
+    std::vector<std::string> params;
+    ast_ptr body;
+
+    definition_defn(std::string n, std::vector<std::string> p, ast_ptr b)
+        : name(std::move(n)), params(std::move(p)), body(std::move(b)) {
+
+    }
+};

02/compile.sh

@@ -0,0 +1,5 @@
+bison -o parser.cpp -d parser.y
+flex -o scanner.cpp scanner.l
+g++ -c -o scanner.o scanner.cpp
+g++ -c -o parser.o parser.cpp
+g++ main.cpp parser.o scanner.o

02/main.cpp

@@ -0,0 +1,14 @@
+#include "ast.hpp"
+#include "parser.hpp"
+
+void yy::parser::error(const std::string& msg) {
+    std::cout << "An error occured: " << std::endl;
+}
+
+extern std::vector<definition_ptr> program;
+
+int main() {
+    yy::parser parser;
+    parser.parse();
+    std::cout << program.size() << std::endl;
+}

02/parser.y

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+%{
+#include <string>
+#include <iostream>
+#include "ast.hpp"
+#include "parser.hpp"
+
+std::vector<definition_ptr> program;
+extern yy::parser::symbol_type yylex();
+
+%}
+
+%token PLUS
+%token TIMES
+%token MINUS
+%token DIVIDE
+%token <int> INT
+%token DEFN
+%token DATA
+%token CASE
+%token OF
+%token OCURLY
+%token CCURLY
+%token OPAREN
+%token CPAREN
+%token COMMA
+%token ARROW
+%token EQUAL
+%token <std::string> LID
+%token <std::string> UID
+
+%language "c++"
+%define api.value.type variant
+%define api.token.constructor
+
+%type <std::vector<std::string>> lowercaseParams
+%type <std::vector<definition_ptr>> program definitions
+%type <std::vector<branch_ptr>> branches
+%type <ast_ptr> aAdd aMul case app appBase
+%type <definition_ptr> definition
+%type <branch_ptr> branch
+%type <pattern_ptr> pattern
+
+%start program
+
+%%
+
+program
+    : definitions { program = std::move($1); }
+    ;
+
+definitions
+    : definitions definition { $$ = std::move($1); $$.push_back(std::move($2)); }
+    | definition { $$ = std::vector<definition_ptr>(); $$.push_back(std::move($1)); }
+    ;
+
+definition
+    : DEFN LID lowercaseParams EQUAL OCURLY aAdd CCURLY
+        { $$ = definition_ptr(
+            new definition_defn(std::move($2), std::move($3), std::move($6))); }
+    ;
+
+lowercaseParams
+    : %empty { $$ = std::vector<std::string>(); }
+    | lowercaseParams LID { $$ = std::move($1); $$.push_back(std::move($2)); }
+    ;
+
+aAdd
+    : aAdd PLUS aMul { $$ = ast_ptr(new ast_binop(PLUS, std::move($1), std::move($3))); }
+    | aAdd MINUS aMul { $$ = ast_ptr(new ast_binop(MINUS, std::move($1), std::move($3))); }
+    | aMul { $$ = std::move($1); }
+    ;
+
+aMul
+    : aMul TIMES app { $$ = ast_ptr(new ast_binop(TIMES, std::move($1), std::move($3))); }
+    | aMul DIVIDE app { $$ = ast_ptr(new ast_binop(DIVIDE, std::move($1), std::move($3))); }
+    | app { $$ = std::move($1); }
+    ;
+
+app
+    : app appBase { $$ = ast_ptr(new ast_app(std::move($1), std::move($2))); }
+    | appBase { $$ = std::move($1); }
+    ;
+
+appBase
+    : INT { $$ = ast_ptr(new ast_int($1)); }
+    | LID { $$ = ast_ptr(new ast_lid(std::move($1))); }
+    | UID { $$ = ast_ptr(new ast_uid(std::move($1))); }
+    | OPAREN aAdd CPAREN { $$ = std::move($2); }
+    | case { $$ = std::move($1); }
+    ;
+
+case
+    : CASE aAdd OF OCURLY branches CCURLY 
+        { $$ = ast_ptr(new ast_case(std::move($2), std::move($5))); }
+    ;
+
+branches
+    : branches COMMA branch { $$ = std::move($1); $1.push_back(std::move($3)); }
+    | branch { $$ = std::vector<branch_ptr>(); $$.push_back(std::move($1));}
+    ;
+
+branch
+    : pattern ARROW OCURLY aAdd CCURLY
+        { $$ = branch_ptr(new branch(std::move($1), std::move($4))); }
+    ;
+
+pattern
+    : LID { $$ = pattern_ptr(new pattern_var(std::move($1))); }
+    | UID lowercaseParams
+        { $$ = pattern_ptr(new pattern_constr(std::move($1), std::move($2))); }
+    ;

02/scanner.l

@@ -0,0 +1,34 @@
+%option noyywrap
+
+%{
+#include <iostream>
+#include "ast.hpp"
+#include "parser.hpp"
+
+#define YY_DECL yy::parser::symbol_type yylex()
+
+%}
+
+%%
+
+[ \n]+ {}
+\+ { return yy::parser::make_PLUS(); }
+\* { return yy::parser::make_TIMES(); }
+- { return yy::parser::make_MINUS(); }
+\/ { return yy::parser::make_DIVIDE(); }
+[0-9]+ { return yy::parser::make_INT(atoi(yytext)); }
+defn { return yy::parser::make_DEFN(); }
+data { return yy::parser::make_DATA(); }
+case { return yy::parser::make_CASE(); }
+of { return yy::parser::make_OF(); }
+\{ { return yy::parser::make_OCURLY(); }
+\} { return yy::parser::make_CCURLY(); }
+\( { return yy::parser::make_OPAREN(); }
+\) { return yy::parser::make_CPAREN(); }
+,  { return yy::parser::make_COMMA(); }
+-> { return yy::parser::make_ARROW(); }
+= { return yy::parser::make_EQUAL(); }
+[a-z][a-zA-Z]* { return yy::parser::make_LID(std::string(yytext)); }
+[A-Z][a-zA-Z]* { return yy::parser::make_UID(std::string(yytext)); }
+
+%%