Data commit

Task/Empty-string/M2000-Interpreter/empty-string-1.m2000

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+A$=""
+Print A$<>"", A$="", Len(A$)=0

Task/Empty-string/M2000-Interpreter/empty-string-2.m2000

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+Module Checkit {
+      \\
+      \\ Part 1: Make global variable, alter it, make a shadow local or global one, use temporary variable
+      \\
+      Global a$="ok"
+      Module Global What {
+            Print a$
+      }
+      Module Checkit {
+            Print a$="ok"
+            a$<=""
+            Print a$=""
+            a$<="ok2"
+            a$=""
+            Print a$="", a$<>""
+            Global  a$="ok again"
+            Module Inner {
+                  Print a$="ok again"
+            }
+            Inner
+            What   \\ now What use new global a$
+            \\ display list of public variables
+            List
+            \\ we can define locals using Def, but raise error if local exist
+            Try {
+                  Def a$="error"
+            }
+            Def b$
+            Print b$=""
+            For This {
+                  \\ block for temporary definitions
+                  For i=1 to 10 {
+                        Local a$=str$(i)
+                  }
+                  \\ we get 10 more a$
+                  List
+                  Print a$=" 10"
+            }
+            Print a$=""
+            List
+            \\ using current stack
+      }
+      \\ we call always a local module, or a global, but not this module,
+      \\ no recursion for standard call for modules.
+      \\ we have to use Call Checkit to call this module recursive
+      Checkit
+      What  \\ now what use old global a$
+      Print a$<>""  ' true
+      List
+
+      \\
+      \\ Part 2:  Pass an empty string to a variable through stack of values
+      \\
+      Module Checkit2 {
+             \\ read make a local by default
+             Read a$
+             Print a$=""  ' true
+             For This {
+                   Push "Hello"
+                   Read New a$
+                   Print a$="Hello"
+                   List
+            }
+            Print a$=""
+      }
+      Checkit2 ""
+      Print a$<>""  ' true
+      Module Checkit3 {
+            \\ using Set we change to global  space, for the end of line
+             Set Read a$
+             Print a$=""  ' true
+             list
+      }
+      Checkit3 ""
+      Print a$<>"" ' true
+      Module Checkit4 {
+            \\ this make a local if no global exist
+            \\ so if global exist, alter the global one
+             Let a$=Letter$
+             Print a$=""  ' true
+             list
+      }
+      Checkit4 ""
+      Print a$="" ' true
+}
+Checkit