sExpression *eval(sExpression *exp, sEnvironment *env){
/* ------------------atom-----------------------*/
/* 1, 10, false, null, "abc" */
if(isSelfEval(exp))
{
return exp;
}
/* a symbol */
else if(isVariable(exp, env))
{
return lookupVariable(toSymb(exp), env);
}
/* ------------------list-----------------------*/
/* (quote blur blur) */
else if(isQuoted(exp))
{
return textOfQuoted(exp);
}
/* (set! name value) */
else if(isAssignment(exp))
{
return evalAssignment(exp, env);
}
/* (define name value) */
else if(isDefinition(exp))
{
return evalDefine(exp, env);
}
/* (define-syntax name ...) */
else if(isDefinitionSyntax(exp))
{
return evalDefineSyntax(exp, env);
}
/* (if blur blur blur) */
else if(isIf(exp))
{
return evalIf(toList(exp), env);
}
/* (lambda (args) (body)) */
else if(isLambdaConst(exp))
{
sList *body;
sList *param = toList( cadr(toList(exp)));
sExpression *temp = cdr(toList( cdr(toList(exp))));
if(isList(temp)){
body = toList(temp);
}else{
body = toList(cons(temp, &sNull));
}
return newLambda(param, body, env);
}
/* (syntax blur blur) syntax rule */
else if(isSymbol(car(toList(exp))) && isSyntaxRule(eval(car(toList(exp)), env)))
{
sExpression *exp2 = evalSyntaxRule(toSyntax(eval(car(toList(exp)), env)), exp);
return eval(exp2, env);
}
/* the other list (x . y) */
else if(isApplication(exp))
{
if(LAZY_EVAL){
sExpression *proexp = actualValue(operator(toList(exp)), env);
if(isLambdaType(proexp) || isPrimitiveProc(proexp)){
sExpression *operand = operands(toList(exp));
return applyLazly(proexp, operand, env);
}
}else{
sExpression *proexp = eval(operator(toList(exp)), env);
if(isLambdaType(proexp) || isPrimitiveProc(proexp)){
sExpression *operand = operands(toList(exp));
sExpression *arguments = listOfValues(operand, env);
return apply(proexp, arguments, env);
}
}
}
return &sError;
}
bool isCompoundStatement() const { return isForKeyword() || isIf(); }
static Statement *statement(void) {
if (isId()) {
Statement *p = NEW(Statement);
p->kind = sAssignment;
p->assignName = getId();
consume();
if (!isEq())
error();
consume();
p->assignValue = expression();
if (isSemi()) {
consume();
}
return p;
} else if (isReturn()) {
Statement *p = NEW(Statement);
p->kind = sReturn;
consume();
p->returnValue = expression();
if (isSemi()) {
consume();
}
return p;
} else if (isLeftBlock()) {
Statement *p = NEW(Statement);
p->kind = sBlock;
consume();
p->block = block();
if (!isRightBlock())
error();
consume();
return p;
} else if (isPrint()) {
Statement *p = NEW(Statement);
p->kind = sPrint;
consume();
p->printValue = expression();
if (isSemi()) {
consume();
}
return p;
} else if (isIf()) {
Statement *p = NEW(Statement);
p->kind = sIf;
consume();
p->ifCondition = expression();
p->ifThen = statement();
if (isElse()) {
consume();
p->ifElse = statement();
} else {
p->ifElse = 0;
}
return p;
} else if (isWhile()) {
Statement *p = NEW(Statement);
p->kind = sWhile;
consume(); /* while */
p->whileCondition = expression();
p->whileBody = statement();
return p;
} else if (isSemi()) {
Statement *p = NEW(Statement);
p->kind = sBlock;
p->block = 0;
consume();
return p;
} else {
return 0;
}
}
