#include <cctype>
#include <iostream>
#include "scan.h"
using namespace std;
const char *Scanner::m_codenames[] = {
"tok_id", "tok_lit", "tok_left", "tok_right", "tok_splat",
"tok_slash", "tok_plus", "tok_minus", "tok_asst", "tok_semi",
"tok_EOF" };
/* Read and return the next token. This also updates the current token to
whatever was read. */
const Scanner::Token & Scanner::next_tok()
{
// The text of the token.
string retext;
// The >> will skip leading blanks.
char inch;
if(!(m_in >> inch))
return m_curr = Token(tok_EOF, "$EOF");
// Let's see what we got.
switch(inch)
{
// A _real_ language would have ranges for this.
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
/* A constant. */
do {
retext += inch;
m_in.get(inch);
} while(isdigit(inch));
m_in.unget();
return m_curr = Token(tok_lit, retext);
// Gak! Identifier.
case 'a': case 'b': case 'c': case 'd': case 'e': case 'f':
case 'g': case 'h': case 'i': case 'j': case 'k': case 'l':
case 'm': case 'n': case 'o': case 'p': case 'q': case 'r':
case 's': case 't': case 'u': case 'v': case 'w': case 'x':
case 'y': case 'z':
case 'A': case 'B': case 'C': case 'D': case 'E': case 'F':
case 'G': case 'H': case 'I': case 'J': case 'K': case 'L':
case 'M': case 'N': case 'O': case 'P': case 'Q': case 'R':
case 'S': case 'T': case 'U': case 'V': case 'W': case 'X':
case 'Y': case 'Z':
/* A constant. */
do {
retext += inch;
m_in.get(inch);
} while(isalpha(inch) || isdigit(inch));
m_in.unget();
return m_curr = Token(tok_id, retext);
case '(':
return m_curr = Token(tok_left, "(");
case ')':
return m_curr = Token(tok_right, ")");
case '*':
return m_curr = Token(tok_splat, "*");
case '/':
return m_curr = Token(tok_slash, "/");
case '+':
return m_curr = Token(tok_plus, "+");
case '-':
return m_curr = Token(tok_minus, "-");
case ';':
return m_curr = Token(tok_semi, "-");
case ':':
m_in.get(inch);
if(inch == '=')
return m_curr = Token(tok_asst, ":=");
else
throw BadInputCharacter(inch);
default:
throw BadInputCharacter(inch);
}
}