Taro writes:
Since the way this would work is that each TYPE would have a string-to-TYPE-value converter, you would just do (inside the compiler)
TYPE.stringconverter = STRINGCONVERTER
and if the compiler encountered a literal with an undefined .stringconverter, it would generate an error to the effect of
Use of TYPE stringconverter 'STRINGCONVERTER' before definition. [...provided that TYPE.stringconverter is set]
If I understand your intent correctly, as things stand this would ordinarily be a runtime NameError,
That is exactly my intent. A more explicit error message than "NameError: name 'myTypeLexer' not defined" would be nice, although if you give the function a reasonably explicit name it should be clear enough. However, a real problem with this idea is that I don't know if the compiler knows how to call the functions it has just compiled! Also, as syntax in general this kind of order dependence would be considered unPythonic, I suspect.
and extra code would need to be added to the compiler to keep track of that: from decimal import Decimal with replacingsyntax float as float x = 1.01 # SyntaxError here??? def Decimal():....
No, it would be a NameError, the name of the implicitly called converter is not defined in scope. The syntax is correct.
For this, the "solution" to keep precision would be along the lines of:
## mycollections.py class MyListFloatHelper(float): def __init__(self, value): self._strvalue = value
class MyList(list): def __init__(self, inlist): for elem in inlist: try: elem = Decimal(elem._strvalue) except AttributeError: pass self.append(elem)
## main.py from mycollections import MyListFloatHelper with readsyntax float from mycollections import MyList with readsyntax list def foo(): myfloat = 1.000000000000000000000000000001 mydlist = [1.0000000000000000000000000001] mydecimal = mydlist[0] print myfloat,"/", mydecimal #==> 1.0 / Decimal("1.0000000000000000000000000001") print type(myfloat), "/", type(mydecimal) #==> <class 'mycollections.MyListFloatHelper'> / <class 'decimal.Decimal'>
You've missed the point. I want myfloat to be a Python builtin float for some reason. Only in the context of a dlist do I want that read syntax to be parsed as a Decimal. You can just require that literal read syntax replacements be global, I guess, but you need to say something about whether this is going to be possible in the proposal.