Fix the fixes. Note that "." had the same problem as "+" and "-", and

that we can still match non-identical constants if they are both
strings with the same numerical value.

simgear/nasal/string.c

@@ -147,8 +147,7 @@ static int readdec(unsigned char* s, int len, int i, double* v)
 
 // Reads a signed integer out of the string starting at i, stores it
 // in v, and returns the next index to start at.  Zero-length
-// decimal numbers (and length-1 strings like '+') are allowed, and
-// are returned as zero.
+// decimal numbers are allowed, and are returned as zero.
 static int readsigned(unsigned char* s, int len, int i, double* v)
 {
     int i0 = i, i2;
@@ -157,10 +156,12 @@ static int readsigned(unsigned char* s, int len, int i, double* v)
     if(s[i] == '+')      { i++; }
     else if(s[i] == '-') { i++; sgn = -1; }
     i2 = readdec(s, len, i, &val);
-    if(i2 == i)
-        return i0; // don't parse "+" or "-" as zero.
+    if(i0 == i && i2 == i) {
+        *v = 0;
+        return i0; // don't successfully parse bare "+" or "-"
+    }
     *v = sgn*val;
-    return i;
+    return i2;
 }
 
 
@@ -183,6 +184,10 @@ static int tonum(unsigned char* s, int len, double* result)
     int i=0, fraclen=0;
     double sgn=1, val, frac=0, exp=0;
 
+    // Special case, "." is not a number, even though "1." and ".0" are.
+    if(len == 1 && s[0] == '.')
+        return 0;
+
     // Read the integer part
     i = readsigned(s, len, i, &val);
     if(val < 0) { sgn = -1; val = -val; }