Fix(parsing): Remove spaces in string before parsing

mapytex/calculus/core/str2.py

@@ -661,7 +661,7 @@ def str2(sink, convert_to_mo=True):
      | > +
      | | > 3
      | | > -4
-    >>> exp = "3-a"
+    >>> exp = "3 - a"
     >>> t = str2tree(exp)
     >>> print(t)
     +
@@ -689,7 +689,7 @@ def str2(sink, convert_to_mo=True):
         else:
             str2_corout = lookforNumbers(operator_corout(missing_times(pparser(sink))))
 
-        for i in expression:
+        for i in expression.replace(" ",""):
             str2_corout.send(i)
         a = str2_corout.throw(STOOOP)