//An entry method for range generation. Implementation of ranges are not provided by a compiler,
//instead a particular data type implement ranges by providing an instance of Enum class. Functions
//succ, enumFrom and enumFromTo are explicitly invoked by this method.
private void CompileRange(ElaExpression parent, ElaRange range, LabelMap map, Hints hints)
{
AddLinePragma(range);
var snd = AddVariable();
var fst = AddVariable();
//Compile the first element which should always be present.
CompileExpression(range.First, map, Hints.None, range);
PopVar(fst);
//If the second element is missing we will calculate it using 'succ'.
if (range.Second == null)
{
var sv = GetFunction("succ", range);
PushVar(fst);
PushVar(sv);
cw.Emit(Op.Call);
PopVar(snd);
}
else
{
CompileExpression(range.Second, map, Hints.None, range);
PopVar(snd);
}
//If a last element is missing we need to generate an infinite range
//using 'enumFrom' function.
if (range.Last == null)
{
var sv = GetFunction("enumFrom", range);
PushVar(snd);
PushVar(fst);
PushVar(sv);
cw.Emit(Op.Call);
cw.Emit(Op.Call);
}
else
{
//An ordinary strict range.
var sv = GetFunction("enumFromTo", range);
PushVar(snd);
PushVar(fst);
CompileExpression(range.Last, map, Hints.None, range);
PushVar(sv);
cw.Emit(Op.Call);
cw.Emit(Op.Call);
cw.Emit(Op.Call);
}
}
//Finds a function from a Enum class - either enumFrom, enumFromTo or succ.
private ScopeVar GetFunction(string name, ElaRange range)
{
var sv = GetGlobalVariable(name, GetFlags.NoError, range.Line, range.Column);
var args = name == "enumFrom" ? 2 : name == "enumFromTo" ? 3 : 1;
//Do some validation to ensure that a found function at least "looks like"
//a correct one - e.g. is a class member and have a correct number of arguments.
if (!options.IgnoreUndefined && (sv.IsEmpty() || (sv.Flags & ElaVariableFlags.ClassFun) != ElaVariableFlags.ClassFun || args != sv.Data))
{
AddError(
name == "enumFrom" ? ElaCompilerError.FromEnumNotFound :
name == "enumFromTo" ? ElaCompilerError.FromEnumToNotFound :
ElaCompilerError.SuccNotFound,
range);
}
return(sv);
}
//This is an old typeId that was used to optimize small ranges (to generate them in-place).
//It is currently not used, but in future it may be rejuvenated.
private bool TryOptimizeRange(ElaRange range, LabelMap map, Hints hints)
{
if (range.First.Type != ElaNodeType.Primitive ||
(range.Second != null && range.Second.Type != ElaNodeType.Primitive) ||
range.Last.Type != ElaNodeType.Primitive)
{
return(false);
}
var fst = (ElaPrimitive)range.First;
var snd = range.Second != null ? (ElaPrimitive)range.Second : null;
var lst = (ElaPrimitive)range.Last;
if (fst.Value.LiteralType != ElaTypeCode.Integer ||
(snd != null && snd.Value.LiteralType != ElaTypeCode.Integer) ||
lst.Value.LiteralType != ElaTypeCode.Integer)
{
return(false);
}
var fstVal = fst.Value.AsInteger();
var sndVal = snd != null?snd.Value.AsInteger() : fstVal + 1;
var lstVal = lst.Value.AsInteger();
var step = sndVal - fstVal;
if (Math.Abs((fstVal - lstVal) / step) > 20)
{
return(false);
}
cw.Emit(Op.Newlist);
if (snd != null)
{
cw.Emit(Op.PushI4, fstVal);
fstVal = sndVal;
cw.Emit(Op.Cons);
}
for (;;)
{
cw.Emit(Op.PushI4, fstVal);
cw.Emit(Op.Cons);
fstVal += step;
if (step > 0)
{
if (fstVal > lstVal)
{
break;
}
}
else if (fstVal < lstVal)
{
break;
}
}
cw.Emit(Op.Genfin);
return(true);
}