Add LexAndYaccCalculator example

tests/LexAndYaccCalculator/LexAndYaccCalculator.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>lexandyacccalculator_example</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="Syntax.fs" />
+    <FsYacc Include="Parser.fsy">
+      <OtherFlags>--module Parser</OtherFlags>
+    </FsYacc>
+    <FsLex Include="Lexer.fsl">
+      <OtherFlags>--module Lexer --unicode</OtherFlags>
+    </FsLex>
+    <Compile Include="Parser.fsi" />
+    <Compile Include="Parser.fs" />
+    <Compile Include="Lexer.fs" />
+    <Compile Include="Program.fs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="FsLexYacc" Version="10.2.0" />
+  </ItemGroup>
+
+</Project>

tests/LexAndYaccCalculator/Lexer.fsl

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+{
+
+open FSharp.Text.Lexing
+open Parser
+
+type Lexbuf =  LexBuffer<char>
+
+let lexeme (lexbuf : Lexbuf) = Lexbuf.LexemeString lexbuf
+
+let newline (lexbuf: LexBuffer<_>) =
+  lexbuf.StartPos <- lexbuf.StartPos.NextLine
+
+}
+
+// Regular expressions
+let whitespace = [' ' '\t' ]
+let newline = ('\n' | '\r' '\n')
+let separator = '_'
+let letter = '\Lu' | '\Ll' | '\Lt' | '\Lm' | '\Lo' | '\Nl'
+let digit = '\Nd'
+let anystring = anychar*
+let integer = digit ((digit | separator)* digit)?
+let char = '\'' ( [^'\\''\n''\r''\t''\b'] | escape_char) '\''
+
+let ident_char =
+      letter
+    | digit
+    | '_'
+let ident = letter ident_char*
+
+let anychar = [^'\n''\r']
+
+let comment = "/*" anystring "*/"
+
+rule tokenstream = parse
+| whitespace	{ tokenstream lexbuf }
+| newline	{ newline lexbuf; tokenstream lexbuf }
+// Identifiers
+| ident         { ID(lexeme lexbuf) }
+| integer       { INT(int (lexeme lexbuf)) }
+// Operators
+| "+"           { OP_PLUS }
+| "-"           { OP_MINUS }
+| "*"           { OP_TIMES }
+| "/"           { OP_DIVIDE }
+// --------------------------
+| _             { failwith ("ParseError" + LexBuffer<_>.LexemeString lexbuf) }
+| eof           { Parser.EOF }

tests/LexAndYaccCalculator/Parser.fsi

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+// Signature file for parser generated by fsyacc
+module Parser
+type token = 
+  | OP_PLUS
+  | OP_MINUS
+  | OP_TIMES
+  | OP_DIVIDE
+  | LPAREN
+  | RPAREN
+  | EOF
+  | INT of (int)
+  | ID of (string)
+type tokenId = 
+    | TOKEN_OP_PLUS
+    | TOKEN_OP_MINUS
+    | TOKEN_OP_TIMES
+    | TOKEN_OP_DIVIDE
+    | TOKEN_LPAREN
+    | TOKEN_RPAREN
+    | TOKEN_EOF
+    | TOKEN_INT
+    | TOKEN_ID
+    | TOKEN_end_of_input
+    | TOKEN_error
+type nonTerminalId = 
+    | NONTERM__startstart
+    | NONTERM_start
+    | NONTERM_Expr
+/// This function maps tokens to integer indexes
+val tagOfToken: token -> int
+
+/// This function maps integer indexes to symbolic token ids
+val tokenTagToTokenId: int -> tokenId
+
+/// This function maps production indexes returned in syntax errors to strings representing the non terminal that would be produced by that production
+val prodIdxToNonTerminal: int -> nonTerminalId
+
+/// This function gets the name of a token as a string
+val token_to_string: token -> string
+val start : (FSharp.Text.Lexing.LexBuffer<'cty> -> token) -> FSharp.Text.Lexing.LexBuffer<'cty> -> ( Syntax.Expr ) 

tests/LexAndYaccCalculator/Parser.fsy

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+%{
+open Syntax
+%}
+
+%start start
+%token <string> ID
+%token <int> INT
+
+%token LPAREN RPAREN EOF
+
+%token OP_PLUS OP_MINUS OP_TIMES OP_DIVIDE
+
+%left OP_PLUS OP_MINUS
+%left OP_TIMES OP_DIVIDE
+%type < Syntax.Expr > start
+
+
+%%
+
+start: Expr { $1 }
+
+Expr: ID  { Var($1) }
+    | INT { Int($1) }
+    | Expr OP_PLUS Expr   { Add($1,$3) }
+    | Expr OP_MINUS Expr  { Sub($1,$3) }
+    | Expr OP_TIMES Expr  { Mul($1,$3) }
+    | Expr OP_DIVIDE Expr { Div($1,$3) }

tests/LexAndYaccCalculator/Program.fs

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+open System.IO
+open FSharp.Text.Lexing
+open Syntax
+
+let testLexerAndParserFromString text expected =
+    let lexbuf = LexBuffer<char>.FromString text
+
+    let parse = Parser.start Lexer.tokenstream lexbuf
+
+    printfn "parse: result = %A, expected %A" parse expected
+
+testLexerAndParserFromString "1" (Int 1)
+testLexerAndParserFromString "hello" (Var "hello")
+testLexerAndParserFromString "1 + 1" (Add((Int 1),(Int 1)))
+testLexerAndParserFromString "1 - 1" (Sub((Int 1),(Int 1)))
+testLexerAndParserFromString "1 * 1" (Mul((Int 1),(Int 1)))
+testLexerAndParserFromString "1 / 1" (Div((Int 1),(Int 1)))
+testLexerAndParserFromString "1 + 2 + 3" (Add(Add(Int 1, Int 2), Int 3))
+testLexerAndParserFromString "1 + 2 * 3" (Add(Int 1, Mul(Int 2, Int 3)))
+testLexerAndParserFromString "1 * 2 + 3" (Add(Mul(Int 1, Int 2), Int 3))

tests/LexAndYaccCalculator/Syntax.fs

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+module Syntax
+
+type Id = Id of string
+
+type Expr =
+    | Var of string
+    | Int of int
+    | Add of Expr * Expr
+    | Sub of Expr * Expr
+    | Mul of Expr * Expr
+    | Div of Expr * Expr