69 lines
2.0 KiB
Java
69 lines
2.0 KiB
Java
package serene.simple;
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import java.io.EOFException;
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import java.io.IOException;
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import java.io.InputStreamReader;
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import java.io.PushbackReader;
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import java.util.List;
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public class Reader {
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public static Node readNode(PushbackReader inputStream) throws IOException {
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char c = (char) inputStream.read();
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inputStream.unread(c);
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if (c == '(') {
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return readList(inputStream);
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}
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else if (Character.isDigit(c)) {
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return readNumber(inputStream);
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}
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else if (c == ')') {
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throw new IllegalArgumentException("Unmatch paranthesis.")
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}
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else {
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return readSymbol(inputStream);
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}
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}
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public static ListNode read(InputStream inputStream) throws IOException {
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return read(new PushbackReader(new InputStreamReader(inputStream)));
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}
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public static ListNode read(PushbackReader inputStream) throws IOException {
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List<Node> nodes = new ArrayList<Node>();
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skipWhitespaces(inputStream);
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char c = inputStream.read();
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while ((byte) c != -1) {
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inputStream.unread(c);
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nodes.add(readNode(inputStream));
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skipWhitespaces(inputStream);
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c = (char) inputStream.read();
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}
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}
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private static Node readList(PushbackReader inputStream) throws IOException {
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char opening = (char) inputStream.read();
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assert opening == '(' : "Lists must start with a '('";
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List<Node> nodes = new ArrayList<Node>();
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do {
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skipWhitespaces(inputStream);
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char c = (char) inputStream.read();
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if (c == ')') {
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break;
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} else if ((byte) c == -1) {
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throw new EOFException("EOF reached before closing of list");
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} else {
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inputStream.unread(c);
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nodes.add(readNode(inputStream));
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}
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} while(true);
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return SpecialForm(ListNode.list(nodes));
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}
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}
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