Add 'IsAutoGlobal'

lib/global.gd

@@ -79,6 +79,23 @@ DeclareGlobalFunction("ValueGlobal");
 ##
 DeclareGlobalFunction("IsBoundGlobal");
 
+#############################################################################
+##
+#F  IsAutoGlobal( <name> )  . . . . . check if a global is automatic
+##
+##  <ManSection>
+##  <Func Name="IsAutoGlobal" Arg='name'/>
+##
+##  <Description>
+##  IsAutoGlobal ( <A>name</A> ) returns true if there is a global variable
+##  named <A>name</A>, declared using 
+##  <Ref Func="DeclareAutoreadableVariables"/>, which has not yet been
+##  accessed. This means reading this variable's value will cause code
+##  to be executed.
+##  </Description>
+##  </ManSection>
+##
+DeclareGlobalFunction("IsAutoGlobal");
 
 #############################################################################
 ##

lib/global.gi

@@ -97,6 +97,21 @@ InstallGlobalFunction( IsBoundGlobal,
 end);
 
 
+#############################################################################
+##
+#M  IsAutoGlobal ( <name> )  . . . .  check if a global is automatic
+## 
+
+
+InstallGlobalFunction( IsAutoGlobal, 
+        function (name)
+    local isauto;
+    CheckGlobalName( name );
+    isauto := IS_AUTO_GVAR(name);
+    Info( InfoGlobal, 3, 
+          "IsAutoGlobal: called for ", name, " returned ", isauto);
+    return isauto;
+end);
 
 #############################################################################
 ##

src/gvars.c

@@ -1085,6 +1085,21 @@ Obj FuncISB_GVAR (
 #endif
 }
 
+/****************************************************************************
+**
+*F  FuncIS_AUTO_GVAR( <self>, <gvar> ) . . check if a global variable is auto
+*/
+
+Obj FuncIS_AUTO_GVAR (
+    Obj                 self,
+    Obj                 gvar )
+{
+    // check the argument
+    RequireStringRep("IS_AUTO_GVAR", gvar);
+    Obj expr = ExprGVar(GVarName( CONST_CSTR_STRING(gvar) ) );
+    return (expr && !IS_INTOBJ(expr)) ? True : False;
+}
+
 
 /****************************************************************************
 **
@@ -1493,6 +1508,7 @@ static StructGVarFunc GVarFuncs[] = {
     GVAR_FUNC(IDENTS_GVAR, 0, ""),
     GVAR_FUNC(IDENTS_BOUND_GVARS, 0, ""),
     GVAR_FUNC(ISB_GVAR, 1, "gvar"),
+    GVAR_FUNC(IS_AUTO_GVAR, 1, "gvar"),
     GVAR_FUNC(ASS_GVAR, 2, "gvar, value"),
     GVAR_FUNC(VAL_GVAR, 1, "gvar"),
     GVAR_FUNC(UNB_GVAR, 1, "gvar"),

tst/testinstall/auto.tst

@@ -0,0 +1,33 @@
+gap> IsAutoGlobal("testglobalvar");
+false
+gap> g := function(x) Print("Checkg\n"); end;;
+gap> f := function(x) Print("Checkf\n"); testglobalvar := 3; end;;
+Syntax warning: Unbound global variable in stream:1
+f := function(x) Print("Checkf\n"); testglobalvar := 3; end;;
+                                                  ^^
+gap> AUTO(g, 1, "testglobalvar");
+gap> IsAutoGlobal("testglobalvar");
+true
+gap> testglobalvar;
+Checkg
+Error, Variable: automatic variable 'testglobalvar' must get a value by functi\
+on call
+gap> AUTO(f, 1, "testglobalvar");
+gap> IsAutoGlobal("testglobalvar");
+true
+gap> testglobalvar;
+Checkf
+3
+gap> IsAutoGlobal("testglobalvar");
+false
+gap> testglobalvar;
+3
+gap> Unbind(testglobalvar);
+gap> IsAutoGlobal("testglobalvar");
+false
+#@if IsHPCGAP
+gap> threadlocalvar := "test";;
+gap> MakeThreadLocal("threadlocalvar");;
+gap> IsAutoGlobal("threadlocalvar");
+false
+#@fi