From 1e304032f0e021c6e2ded28bf6adfbd5e692ef75 Mon Sep 17 00:00:00 2001
From: Sameer Rahmani <lxsameer@gnu.org>
Date: Mon, 30 Dec 2019 22:30:09 +0000
Subject: [PATCH] MinusFn has been added

---
 src/main/java/serene/simple/Reader.java    | 20 +++++++--
 src/main/java/serene/simple/RootScope.java |  5 ++-
 src/main/java/serene/simple/SNumber.java   | 50 ++++++++++++++++++++++
 3 files changed, 69 insertions(+), 6 deletions(-)

diff --git a/src/main/java/serene/simple/Reader.java b/src/main/java/serene/simple/Reader.java
index 93ca246..4536469 100644
--- a/src/main/java/serene/simple/Reader.java
+++ b/src/main/java/serene/simple/Reader.java
@@ -31,17 +31,21 @@ import java.util.List;
 public class Reader {
   public static Node readNode(PushbackReader inputStream) throws IOException, IllegalArgumentException, SereneException {
     char c = (char) inputStream.read();
+    char nextChar = (char) inputStream.read();
+
+    inputStream.unread(nextChar);
     inputStream.unread(c);
 
     if (c == '(') {
       return readList(inputStream);
     }
-    else if (Character.isDigit(c)) {
-      return readNumber(inputStream);
-    }
     else if (c == '"') {
       return readString(inputStream);
     }
+    else if (Character.isDigit(c) ||
+             (c == '-' && Character.isDigit(nextChar))) {
+      return readNumber(inputStream);
+    }
     else if (c == ')') {
       throw new IllegalArgumentException("Unmatch paranthesis.");
     }
@@ -51,7 +55,9 @@ public class Reader {
   }
 
   public static ListNode<Node> read(InputStream inputStream) throws IOException, IllegalArgumentException, SereneException {
-    return read(new PushbackReader(new InputStreamReader(inputStream)));
+    // The number two is the buffer size, we need a bigger buffer than
+    // just one byte to be able to read ahead and undo reads
+    return read(new PushbackReader(new InputStreamReader(inputStream), 2));
   }
 
   public static ListNode<Node> read(PushbackReader inputStream) throws IOException, IllegalArgumentException, SereneException {
@@ -126,6 +132,12 @@ public class Reader {
     int ch = inputStream.read();
     String number = "";
 
+    if (Character.isDigit((char) ch) || ch == '-') {
+      number = number + (char) ch;
+    }
+
+    ch = inputStream.read();
+
     while (Character.isDigit((char) ch)) {
       number = number + (char) ch;
       ch = inputStream.read();
diff --git a/src/main/java/serene/simple/RootScope.java b/src/main/java/serene/simple/RootScope.java
index e755265..b5a0332 100644
--- a/src/main/java/serene/simple/RootScope.java
+++ b/src/main/java/serene/simple/RootScope.java
@@ -25,6 +25,7 @@ import java.util.Map;
 import serene.simple.builtin.PrintlnFn;
 import serene.simple.builtin.QuitFn;
 import serene.simple.builtin.PlusFn;
+import serene.simple.builtin.MinusFn;
 import serene.simple.builtin.NewFn;
 
 public class RootScope extends AScope {
@@ -33,13 +34,13 @@ public class RootScope extends AScope {
       put("println", new PrintlnFn());
       put("quit", new QuitFn());
       put("+", new PlusFn());
+      put("-", new MinusFn());
       put("System", System.class);
       put("Boolean", Boolean.class);
       put("String", String.class);
       put("new", new NewFn());
     }};
-  // "+", PlusFn,
-  // "-", MinusFn,
+
   // "*", TimesFn,
   // "/", ObelusFn,
   // "mod", ModFn,
diff --git a/src/main/java/serene/simple/SNumber.java b/src/main/java/serene/simple/SNumber.java
index e699b04..e97b4c3 100644
--- a/src/main/java/serene/simple/SNumber.java
+++ b/src/main/java/serene/simple/SNumber.java
@@ -27,6 +27,9 @@ public class SNumber {
     public IOps add(Object x);
     public IOps add(Double x);
     public IOps add(Long x);
+    public IOps subtract(Object x);
+    public IOps subtract(Double x);
+    public IOps subtract(Long x);
 
     public Object value();
   }
@@ -61,6 +64,25 @@ public class SNumber {
       return y.add(this.v);
     }
 
+    public IOps subtract(Object x) throws SereneException {
+      if (x instanceof Long) {
+        return this.subtract((long) x);
+      }
+      else if (x instanceof Double) {
+        return this.subtract((Double) x);
+      }
+      throw new SereneException("Can't cast anything beside Long and Double");
+    }
+
+    public IOps subtract(Long x) {
+      return new LongNumber(this.v - x);
+    }
+
+    public IOps subtract(Double x) {
+      DoubleNumber y = new DoubleNumber(x);
+      return y.subtract(this.v);
+    }
+
     public Object value() {
       return this.v;
     }
@@ -91,8 +113,36 @@ public class SNumber {
       return new DoubleNumber(this.v + x.doubleValue());
     }
 
+    public IOps subtract(Object x) throws SereneException {
+      if (x instanceof Long) {
+        return this.subtract((long) x);
+      }
+      else if (x instanceof Double) {
+        return this.subtract((Double) x);
+      }
+      throw new SereneException("Can't cast anything beside Long and Double");
+    }
+
+    public IOps subtract(Double x) {
+      return new DoubleNumber(this.v - x);
+    }
+
+    public IOps subtract(Long x) {
+      return new DoubleNumber(this.v - x.doubleValue());
+    }
+
     public Object value() {
       return this.v;
     }
   }
+
+  public static IOps createNumber(Object num) {
+    if (num instanceof Long) {
+      return new SNumber.LongNumber((long) num);
+    }
+    else if (num instanceof Double) {
+      return new SNumber.DoubleNumber((Double) num);
+    }
+    throw new SereneException("Can't cast anything beside Long and Double");
+  }
 }