On Tue, 2020-05-19 at 15:21 +0100, Tim Murphy wrote: > A question would be do we want to use GMP or are 64 bit ints enough? > I'm inclined to say ints are ok of they are wide.
Straight 64bit integer arithmetic is fine IMO. I'm definitely not interested in adding another library dependency. > So for me an add function that took signed numbers would be enough if > it came with < > = since we already have "or" and "and". e.g. > X:=$(add $(X),-1) gives you decrement. > > If one is minimal then there is less chance of creating a carbuncle. No, I don't like this. Perhaps addition is sufficient for your use- case but others may need multiplication or division and I certainly don't want to start adding 10 different explicit funtions like "add", "mult", etc. I prefer a single mathematical expression function. These are the things that need to be decided from what I can tell: Name: I'm using expr here just for convenience. Is there a better name? Whitespace: do we have to put whitespace around every operator, like expr(1), or is the function smart enough to understand $(expr 1+1+4)? Grouping: do we try to implement expression grouping with () (e.g., $(expr (1 + 1) * 4) or is it good enough to just say people need to nest expr functions: $(expr $(expr 1 + 1) * 4)? Precedence: do we try to implement standard mathematical precedence (multiplication/division before addition/subtraction) or do we just evaluate left to right and require explicit grouping? It would definitely be a source of ongoing user confusion to not follow normal precedence rules, but supporting it would make the implementation more complex. Increment/decrement: do we try to implement += / -= and/or ++ --? It would be something like the symbol on the left would be interpreted as a variable name, so $(expr foo += 5) would add 5 to the variable foo (and expand to the new value of $(foo)). If we support ++/-- do we support both pre- and post- operators? This isn't needed in places where you can just say "foo = $(expr $(foo) + 5)", but allowing assignment within an expression could be very helpful. It could be done anyway with: $(eval foo := $(expr $(foo) + 5))$(foo) ... is it worthwhile to add syntactic sugar for this? If we support increment/decrement do we go farther and support variable interpolation a la shell $((...)), where a symbol is assumed to be the value of the variable (that is, $(expr foo + 10) is equivalent to $(expr $(foo) + 10)? I wouldn't bother implementing this by itself but it becomes a question if increment/decrement needs it anyway.
