/* Normally, Flex will call yywrap when reaching an end-of-file. We don't want
   * to deal with files anyway, so let's just disable this. */
  %option noyywrap
  
  /* WARNING:
   * If you think about using the bison-bridge option, note that this assumes
   * that the bison parser is reentrant (pure-parser option).
   *
   * Note also that bison and flex (when not reentrant) communicate with each
   * other by using global variables such as yylval or yylineno, these variables
   * will also be prefixed (here we have poicare_expression_yylval).
   *
   * When using a reentrant parser, these variables become pointers and are
   * not prefixed (this is probably a bug in bison, or at least is a bug in my
   * opinion).
   *
   * Using reentrant parsers and lexer is not useful for us as we neither use
   * multiple inputs, different threads calling the lexer-parser nor do we read
   * nested files.
   */
  
  /* Normally, on each new input file the scanner calls isatty() in an attempt to
   * determine whether the scanner's input source is interactive and thus should
   * be read a character at a time.
   * We obviously do *not* provide isatty(), and we know we're never going to use
   * an interactive input source. */
  %option never-interactive
  
  %{
  /* Flex generate a lexer, a function that outputs tokens.
   * Those tokens (and the optional value that they can be attached) are defined
   * in the Bison grammar. To use those token definitions, we need to include the
   * header generated by Bison.
   * Also, since some tokens can have an "Expression *" value attached, we'll
   * need "Expression" to be defined before including that header.
   * We could use the '%code requires{}' directive to make sure that Expression is
   * well defined in the parser header, but this directive only comes in bison 3,
   * which is not installed by default on MacOS, we thus made the choice to prefer
   * compatibility with MacOS's default version (2.3) instead of using the code
   * requires feature. */
  #include <cmath>
  #include <poincare.h>
  #include "expression_parser.hpp"
  using namespace Poincare;
  
  /* Flex has provision for reading files. We'll never use this, so we're defining
   * YY_INPUT which effectively disables taking input from a file. */
  #define YY_INPUT
  
  /* Flex can print to stdout what token it matches by calling the ECHO function.
   * We don't want that feature : we don't even have printf ! */
  #define ECHO
  
  /* This defines the size of the flex buffer size.
   * By default this buffer is of 16k, but we don't have the luxury to use so much
   * memory on a microcontroller.
   * The choice of 256 Bytes is the size of the input buffer given to flex in the
   * current implementation (the app takes a maximum of 256).
   */
  #undef YY_BUF_SIZE
  #define YY_BUF_SIZE 256
  
  #define fprintf(...) ((void)0)
  #define exit(...) abort()
  
  %}
  
  %%
  
   /* If two patterns can match the same input, flex resolves the ambiguity:
    * - By matching the longest possible string
    * - In a tie, by using the pattern that appears first
    *
    * Also note that yytext is guaranteed to be null-terminated when the token is
    * being built, (i.e. when flex calls our code snippet), but this is achieved
    * by flex temporarily swapping the last character. Afterwards the pointer is
    * still valid but the string isn't null-terminated anymore.
    */
    /* We designed our own extended-ASCII to include requiered symbols in less
     * than 255 glyphs. The file ion/include/ion/charset.h lists all added
     * non-ASCII symbols with their char associated. For example, the char \x89
     * refered to Pi symbols. This artefact leads to the following lexer rules
     * starting with \x. */
  
  [0-9]+ { poincare_expression_yylval.string.address = yytext; poincare_expression_yylval.string.length = yyleng; return DIGITS; }
  [A-Zxn] { poincare_expression_yylval.character = yytext[0]; return SYMBOL; }
  M[0-9] { poincare_expression_yylval.character = Symbol::matrixSymbol(yytext[1]); return SYMBOL; }
  u\(n\) { poincare_expression_yylval.character = Symbol::SpecialSymbols::un; return SYMBOL; }
  u\(n\+1\) { poincare_expression_yylval.character = Symbol::SpecialSymbols::un1; return SYMBOL; }
  v\(n\) { poincare_expression_yylval.character = Symbol::SpecialSymbols::vn; return SYMBOL; }
  v\(n\+1\) { poincare_expression_yylval.character = Symbol::SpecialSymbols::vn1; return SYMBOL; }
  acos { poincare_expression_yylval.expression = new ArcCosine(); return FUNCTION; }
  acosh { poincare_expression_yylval.expression = new HyperbolicArcCosine(); return FUNCTION; }
  abs { poincare_expression_yylval.expression = new AbsoluteValue(); return FUNCTION; }
  ans { poincare_expression_yylval.character = Symbol::SpecialSymbols::Ans; return SYMBOL; }
  arg { poincare_expression_yylval.expression = new ComplexArgument(); return FUNCTION; }
  asin { poincare_expression_yylval.expression = new ArcSine(); return FUNCTION; }
  asinh { poincare_expression_yylval.expression = new HyperbolicArcSine(); return FUNCTION; }
  atan { poincare_expression_yylval.expression = new ArcTangent(); return FUNCTION; }
  atanh { poincare_expression_yylval.expression = new HyperbolicArcTangent(); return FUNCTION; }
  binomial { poincare_expression_yylval.expression = new BinomialCoefficient(); return FUNCTION; }
  ceil { poincare_expression_yylval.expression = new Ceiling(); return FUNCTION; }
  confidence { poincare_expression_yylval.expression = new ConfidenceInterval(); return FUNCTION; }
  diff { poincare_expression_yylval.expression = new Derivative(); return FUNCTION; }
  dim { poincare_expression_yylval.expression = new MatrixDimension(); return FUNCTION; }
  det { poincare_expression_yylval.expression = new Determinant(); return FUNCTION; }
  conj { poincare_expression_yylval.expression = new Conjugate(); return FUNCTION; }
  cos { poincare_expression_yylval.expression = new Cosine(); return FUNCTION; }
  cosh { poincare_expression_yylval.expression = new HyperbolicCosine(); return FUNCTION; }
  factor { poincare_expression_yylval.expression = new Factor(); return FUNCTION; }
  floor { poincare_expression_yylval.expression = new Floor(); return FUNCTION; }
  frac { poincare_expression_yylval.expression = new FracPart(); return FUNCTION; }
  gcd { poincare_expression_yylval.expression = new GreatCommonDivisor(); return FUNCTION; }
  im { poincare_expression_yylval.expression = new ImaginaryPart(); return FUNCTION; }
  int { poincare_expression_yylval.expression = new Integral(); return FUNCTION; }
  inverse { poincare_expression_yylval.expression = new MatrixInverse(); return FUNCTION; }
  lcm { poincare_expression_yylval.expression = new LeastCommonMultiple(); return FUNCTION; }
  ln { poincare_expression_yylval.expression = new NaperianLogarithm(); return FUNCTION; }
  log { poincare_expression_yylval.expression = new Logarithm(); return FUNCTION; }
  permute { poincare_expression_yylval.expression = new PermuteCoefficient(); return FUNCTION; }
  prediction95 { poincare_expression_yylval.expression = new PredictionInterval(); return FUNCTION; }
  prediction { poincare_expression_yylval.expression = new ConfidenceInterval(); return FUNCTION; }
  product { poincare_expression_yylval.expression = new Product(); return FUNCTION; }
  quo { poincare_expression_yylval.expression = new DivisionQuotient(); return FUNCTION; }
  random { poincare_expression_yylval.expression = new Random(); return FUNCTION; }
  randint { poincare_expression_yylval.expression = new Randint(); return FUNCTION; }
  re { poincare_expression_yylval.expression = new RealPart(); return FUNCTION; }
  rem { poincare_expression_yylval.expression = new DivisionRemainder(); return FUNCTION; }
  root { poincare_expression_yylval.expression = new NthRoot(); return FUNCTION; }
  round { poincare_expression_yylval.expression = new Round(); return FUNCTION; }
  sin { poincare_expression_yylval.expression = new Sine(); return FUNCTION; }
  sinh { poincare_expression_yylval.expression = new HyperbolicSine(); return FUNCTION; }
  sum { poincare_expression_yylval.expression = new Sum(); return FUNCTION; }
  tan { poincare_expression_yylval.expression = new Tangent(); return FUNCTION; }
  tanh { poincare_expression_yylval.expression = new HyperbolicTangent(); return FUNCTION; }
  trace { poincare_expression_yylval.expression = new MatrixTrace(); return FUNCTION; }
  transpose { poincare_expression_yylval.expression = new MatrixTranspose(); return FUNCTION; }
  undef { poincare_expression_yylval.expression = new Undefined(); return UNDEFINED; }
  inf { poincare_expression_yylval.expression = new Undefined(); return UNDEFINED; }
  \x89 { poincare_expression_yylval.character = yytext[0]; return SYMBOL; }
  \x8c { return EE; }
  \x90 { poincare_expression_yylval.expression = new SquareRoot(); return FUNCTION; }
  \x8b { poincare_expression_yylval.character = yytext[0]; return SYMBOL; }
  \x8e { poincare_expression_yylval.character = yytext[0]; return SYMBOL; }
  \x8f { return STO; }
  \+ { return PLUS; }
  \- { return MINUS; }
  \x93 { return MULTIPLY; }
  \* { return MULTIPLY; }
  \/ { return DIVIDE; }
  \^ { return POW; }
  \! { return BANG; }
  \( { return LEFT_PARENTHESIS; }
  \) { return RIGHT_PARENTHESIS; }
  \{ { return LEFT_BRACE; }
  \} { return RIGHT_BRACE; }
  \[ { return LEFT_BRACKET; }
  \] { return RIGHT_BRACKET; }
  \, { return COMMA; }
  \. { return DOT; }
  [ ]+ /* Ignore whitespaces */
  . { return UNDEFINED_SYMBOL; }
  
  %%