func pushExpression(expression *parser.Node, table *SymbolTable) string {
if expression == nil {
panic("argument must not be nil")
}
if expression.Name != "expression" {
panic(fmt.Sprintf("argument must be `expression`, but actual: %v", expression.ToXML()))
}
leftTerm, _ := expression.Find(&parser.Node{Name: "term"})
result := compileTerm(leftTerm, table)
if len(expression.Children) > 1 {
operator := expression.Children[1]
expression.Children = expression.Children[2:]
result += pushExpression(expression, table)
result += compileOperator(operator.Value)
}
return result
}
func pushStatements(statements *parser.Node, table *SymbolTable) string {
result := ""
for _, statement := range statements.Children {
switch statement.Name {
case "letStatement":
identifier, _ := statement.Find(&parser.Node{Name: "identifier"})
symbol := table.Get(identifier.Value)
if symbol == nil {
panic(fmt.Sprintf("variable `%v` is not defined: %v\n%v", identifier.Value, table.String(), statements.ToXML()))
}
bracket, _ := statement.Find(&parser.Node{Name: "symbol", Value: "["})
if bracket != nil {
expressions := statement.FindAll(&parser.Node{Name: "expression"})
result += pushExpression(expressions[0], table)
result += pushSymbol(symbol)
result += "add\n"
result += pushExpression(expressions[1], table)
result += "pop temp 0\n"
result += "pop pointer 1\n"
result += "push temp 0\n"
result += "pop that 0\n"
} else {
expression, _ := statement.Find(&parser.Node{Name: "expression"})
result += pushExpression(expression, table)
result += popSymbol(symbol)
}
case "doStatement":
subroutineCall := &parser.Node{Name: "subroutineCall", Children: statement.Children[1 : len(statement.Children)-1]}
result += compileSubroutineCall(subroutineCall, table)
result += "pop temp 0\n"
case "returnStatement":
expression, _ := statement.Find(&parser.Node{Name: "expression"})
if expression != nil {
result += pushExpression(expression, table)
} else {
result += "push constant 0\n"
}
result += "return\n"
case "ifStatement":
ifExpression, _ := statement.Find(&parser.Node{Name: "expression"})
ifStatementsList := statement.FindAll(&parser.Node{Name: "statements"})
trueLabel := uniqueLabel("IF_TRUE")
falseLabel := uniqueLabel("IF_FALSE")
endLabel := uniqueLabel("IF_END")
if len(ifStatementsList) > 1 {
ifStatements, elseStatements := ifStatementsList[0], ifStatementsList[1]
result += pushExpression(ifExpression, table)
result += "if-goto " + trueLabel + "\n"
result += "goto " + falseLabel + "\n"
result += "label " + trueLabel + "\n"
result += pushStatements(ifStatements, table)
result += "goto " + endLabel + "\n"
result += "label " + falseLabel + "\n"
result += pushStatements(elseStatements, table)
result += "label " + endLabel + "\n"
} else {
ifStatements := ifStatementsList[0]
result += pushExpression(ifExpression, table)
result += "if-goto " + trueLabel + "\n"
result += "goto " + falseLabel + "\n"
result += "label " + trueLabel + "\n"
result += pushStatements(ifStatements, table)
result += "label " + falseLabel + "\n"
}
case "whileStatement":
expLabel := uniqueLabel("WHILE_EXP")
endLabel := uniqueLabel("WHILE_END")
result += "label " + expLabel + "\n"
whileExpression, _ := statement.Find(&parser.Node{Name: "expression"})
result += pushExpression(whileExpression, table)
result += "not\n"
result += "if-goto " + endLabel + "\n"
whileBody, _ := statement.Find(&parser.Node{Name: "statements"})
result += pushStatements(whileBody, table)
result += "goto " + expLabel + "\n"
result += "label " + endLabel + "\n"
}
}
return result
}