#header <<
#include <stdlib.h>

typedef double Attrib;
>>

<<
main()
{
    ANTLR(statement(), stdin);
}

int
zzd_attr(Attrib *attr)
{
    if (attr != NULL ) {
        free(attr);
        attr = NULL;
    }
}

int
zzcr_attr(Attrib *attr, int token, char *text)
{
    char c;

    switch (token) {
    case Number:
        *attr = atof(text); break;
    case Symbol:
        *attr = text[0] - 'a'; break;
    }
}

static double vbltable[26];

double
gensym(char c, double num) {
    vbltable[c] = num;
    return num;
}

double
lookup(char c) {
    return vbltable[c];
}

>>

#token "[\t\ \r]" <<zzskip();>> /* Ignore White */
#token Number "([0-9]+|([0-9]*\.[0-9]+){[eE]{[\+\-]}[0-9]+})"
#token Symbol "[a-z]"

statement
    : (expressions)* "@"
        <<printf("bye.\n");>>
;

expressions
    : Symbol "=" expr <<$expressions = gensym($1.1, $3);>> "\n" <<printf("%g\n", lookup($1));>>
    | expr "\n" <<printf("%g\n", $1);>>
    | "\n" /* empty line */
;

expr
    : mexpr <<$expr = $1;>>
    ( "\+" mexpr <<$expr += $2;>> |
      "\-" mexpr <<$expr -= $2;>> )*
;

mexpr
    : unary <<$mexpr = $1;>>
    ( "\*" unary <<$mexpr *= $2;>> |
      "\/" unary <<$mexpr /= $2;>> )*
;

unary
    : prim <<$unary = $1;>>
    | "\-" prim <<$unary = -$2;>>
;

prim
    : "\(" expr "\)" <<$prim = $2;>>
    | Number <<$prim = $1;>>
    | Symbol <<$prim = lookup($1);>>
;