Merge pull request #55 from rfhits/main

fix: support minus operator

Author: ohkimur

chapter_4/exercise_4_03/calculator.c

@@ -143,13 +143,19 @@ int getop(char s[])
   if (c == '-')
   {
     int next = getch();
-    if (!isdigit(next) && next != '.')
+    if (next == '\n' || next == ' ' || next == '\t')
     {
-      return next;
+      ungetch(next);
+      return c; // return '-' as operator
+    }
+    else if (!isdigit(next) && next != '.')
+    {
+      return next; // not a number
+    }
+    else // number like "-5", "-.6" etc, next is digit or '.'
+    {
+      s[++i] = c = next;
     }
-
-    s[i] = c;
-    ungetch(c = next);
   }
   else
   {

chapter_4/exercise_4_04/stack.c

@@ -201,13 +201,19 @@ int getop(char s[])
   if (c == '-')
   {
     int next = getch();
-    if (!isdigit(next) && next != '.')
+    if (next == '\n' || next == ' ' || next == '\t')
     {
-      return next;
+      ungetch(next);
+      return c; // return '-' as operator
+    }
+    else if (!isdigit(next) && next != '.')
+    {
+      return next; // not a number
+    }
+    else // number like "-5", "-.6" etc, next is digit or '.'
+    {
+      s[++i] = c = next;
     }
-
-    s[i] = c;
-    ungetch(c = next);
   }
   else
   {

chapter_4/exercise_4_05/math.c

@@ -215,13 +215,19 @@ int getop(char s[])
   if (c == '-')
   {
     int next = getch();
-    if (!isdigit(next) && next != '.')
+    if (next == '\n' || next == ' ' || next == '\t')
     {
-      return next;
+      ungetch(next);
+      return c; // return '-' as operator
+    }
+    else if (!isdigit(next) && next != '.')
+    {
+      return next; // not a number
+    }
+    else // number like "-5", "-.6" etc, next is digit or '.'
+    {
+      s[++i] = c = next;
     }
-
-    s[i] = c;
-    ungetch(c = next);
   }
   else
   {

chapter_4/exercise_4_06/variables.c

@@ -258,13 +258,19 @@ int getop(char s[])
   if (c == '-')
   {
     int next = getch();
-    if (!isdigit(next) && next != '.')
+    if (next == '\n' || next == ' ' || next == '\t')
     {
-      return next;
+      ungetch(next);
+      return c; // return '-' as operator
+    }
+    else if (!isdigit(next) && next != '.')
+    {
+      return next; // not a number
+    }
+    else // number like "-5", "-.6" etc, next is digit or '.'
+    {
+      s[++i] = c = next;
     }
-
-    s[i] = c;
-    ungetch(c = next);
   }
   else
   {

chapter_4/exercise_4_10/calculator.c

@@ -267,14 +267,19 @@ int getop(char s[])
   if (c == '-')
   {
     int next = line[line_i++];
-    if (!isdigit(next) && next != '.')
+    if (next == '\n' || next == ' ' || next == '\t' || next == '\0')
+    {
+      --line_i;
+      return '-';
+    }
+    else if (!isdigit(next) && next != '.') // not a number
     {
       return next;
     }
-
-    s[i] = c;
-    c = next;
-    --line_i;
+    else
+    {
+      s[++i] = c = next;
+    }
   }
   else
   {