// Integer arithmetic interpreter value (avalue)
// definition.
//
// File:        iavalue.cc
// Author:      course
// Version:     2
//
// This file defines the arithmetic interpreter value
// type, or avalue.

#include "lexeme.h"     // Defines lexemes, includes
			// avalue.h.

// `Zero' avalue, which becomes value of empty program.
//
avalue zero_avalue = 0;

// Produce an avalue from a lexeme, which must be a
// LEX_NUMBER or a LEX_SYMBOL.
//
avalue evaluate (lexeme lex)
{
    if (lex->type == LEX_NUMBER) return lex->value;
    else if (lex->type == LEX_SYMBOL)
    {
	if (lex->inited) return lex->value;
	else error ("Undefined symbol: ", lex->pname);
    }
    else assert (false); // We should never execute
			 // this.
}


// Assign to a lexeme.  Returns the value assigned.
//
avalue assign (lexeme lex, avalue v)
{
    assert (lex->type == LEX_SYMBOL);

    lex->value      = v;
    lex->inited     = true;

    return v;
}

// Initialize avalues.
//
void init_avalues (void) {}