parser Class Reference

#include <parse.hpp>

List of all members.

Public Member Functions
	parser (std::istream &input)
bool	get_expr (double &result)
Private Member Functions
std::string	charify (char c)
bool	get_number (double &result)
bool	get_primary (double &result)
bool	get_mult_expr (double &result)
Private Attributes
std::istream &	input_
std::ctype< char > const &	ctype_

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Detailed Description

Parser class template.

Definition at line 17 of file parse.hpp.

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Constructor & Destructor Documentation

parser::parser

(

std::istream &

input

)

Constructor. Save the input stream.

Parameters:

input

The input stream

Definition at line 5 of file parse.cpp.

: input_(input),
  ctype_(std::use_facet<std::ctype<char> >(input.getloc()))
{}

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Member Function Documentation

bool parser::get_expr

(

double &

result

)

Read one expression and store the result in result.

Parameters:

result

Where to store the result of the expression.

Returns:

true to continue or false to end the loop

Exceptions:

parse_error

for various syntax and other errors

Definition at line 109 of file parse.cpp.

References get_mult_expr(), and input_.

Referenced by get_primary(), and parse_loop().

{
  if (not get_mult_expr(result))
    return false;
  char c;
  while (input_ >> c) {
    if (c != '+' and c != '-') {
      input_.unget();
      return true;
    } else {
      double right;
      if (not get_mult_expr(right))
        throw parse_error("syntax error: unterminated expression. Expected a multiplicative-exprssion after " + c);
      if (c == '+')
        result += right;
      else
        result -= right;
    }
  }
  return true;
}

std::string parser::charify

(

char

c

)

[private]

Convert a characer to a readable form.

Parameters:

c

The character

Returns:

A C++-style character literal that ensures c is readable.

Definition at line 10 of file parse.cpp.

References ctype_.

Referenced by get_number(), and get_primary().

{
  if (c == '\a') return "\'\\a\'";
  if (c == '\b') return "\'\\b\'";
  if (c == '\f') return "\'\\f\'";
  if (c == '\n') return "\'\\n\'";
  if (c == '\r') return "\'\\r\'";
  if (c == '\t') return "\'\\t\'";
  if (c == '\v') return "\'\\v\'";
  if (c == '\'') return "\'\\'\'";
  if (c == '\\') return "\'\\\\\'";

  if (ctype_.is(ctype_.print, c))
    return std::string("\'") + c + '\'';
  else {
    std::ostringstream stream;
    stream << "'\\x" << std::hex;
    stream.fill('0');
    stream.width(2);
    stream << (std::char_traits<char>::to_int_type(c) & 0xFF) << '\'';
    return stream.str();
  }
}

bool parser::get_number

(

double &

result

)

[private]

Parse a number.

Parameters:

result

Store the number here

Returns:

true to continue parsing or false to stop (end of file or error)

Definition at line 37 of file parse.cpp.

References charify(), and input_.

Referenced by get_primary().

{
  std::string token;
  char c;
  if (not input_.get(c))
    return false;
  if (c == '+' or c == '-') {
    token += c;
    if (not input_.get(c))
      throw parse_error("unterminated number: expected a digit after the sign");
  }
  if (c < '0' or c > '9') {
    input_.unget();
    throw parse_error("syntax error: expected digit, got " + charify(c));
  }
  while (c >= '0' and c <= '9') {
    token += c;
    if (not input_.get(c)) {
      std::istringstream tmp(token);
      // If the value overflows, return false.
      return (tmp >> result);
    }
  }
  if (c == '.') {
    token += c;
    if (not input_.get(c))
      throw parse_error("unterminated number: expected digit after the decimal point");
    if (c < '0' or c > '9') {
      input_.unget();
      throw parse_error("syntax error: expected digit after decimal point, got " + charify(c));
    }
    while (c >= '0' and c <= '9') {
      token += c;
      if (not input_.get(c)) {
        std::istringstream tmp(token);
        // If the value overflows or is otherwise invalid, return false.
        return (tmp >> result);
      }
    }
  }
  if (c == 'e' or c == 'E') {
    token += c;
    if (not input_.get(c))
      throw parse_error("unterminated number: expected digit in the exponent");
    if (c == '-' or c == '+') {
      token += c;
      if (not input_.get(c))
        throw parse_error("unterminated number: expected digit after sign in the exponent");
    }
    if (c < '0' or c > '9') {
      input_.unget();
      throw parse_error("syntax error: expected digit in the exponent, got " + charify(c));
    }
    while (c >= '0' and c <= '9') {
      token += c;
      if (not input_.get(c)) {
        std::istringstream tmp(token);
        // If the value overflows or is otherwise invalid, return false.
        return (tmp >> result);
      }
    }
  }
  input_.unget();

  std::istringstream tmp(token);
  // If the value overflows or is otherwise invalid, return false.
  return (tmp >> result);
}

bool parser::get_primary

(

double &

result

)

[private]

Parse a primary expression. A primary is a parenthesized expression or a numeric literal.

Parameters:

result

Store the number here

Returns:

true to continue parsing or false to stop (end of file or error)

Definition at line 161 of file parse.cpp.

References charify(), get_expr(), get_number(), and input_.

Referenced by get_mult_expr().

{
  char c;
  if (not (input_ >> c))
    // Can't read one character, so must be end-of-file
    return false;
  else if (c == '(') {
    if (not get_expr(result))
      return false;
    if (not (input_ >> c))
      throw parse_error("syntax error: EOF when expecting ')'");
    else if (c != ')')
      throw parse_error("syntax error: expected ')', but got " + charify(c));
    else
      return true;
  } else {
    input_.unget();
    return get_number(result);
  }
}

bool parser::get_mult_expr

(

double &

result

)

[private]

Parse a multiplicative expression.

Parameters:

result

Store the number here

Returns:

true to continue parsing or false to stop (end of file or error)

Definition at line 134 of file parse.cpp.

References get_primary(), and input_.

Referenced by get_expr().

{
  if (not get_primary(result))
    return false;
  char c;
  while (input_ >> c) {
    if (c != '*' and c != '/') {
      input_.unget();
      return true;
    } else {
      double right;
      if (not get_primary(right))
        throw parse_error("syntax error: unterminated expression. Expected a primary after " + c);
      if (c == '*')
        result *= right;
      else if (right == 0.0)
        throw parse_error("division by zero");
      else
        result /= right;
    }
  }
  return true;
}

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Member Data Documentation

std::istream& parser::input_ [private]

Definition at line 55 of file parse.hpp.

Referenced by get_expr(), get_mult_expr(), get_number(), and get_primary().

std::ctype<char> const& parser::ctype_ [private]

Definition at line 56 of file parse.hpp.

Referenced by charify().

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The documentation for this class was generated from the following files:

• parse.hpp
• parse.cpp

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