On Fri, Dec 19, 2014 at 02:05:30PM -0800, Matthew Butterick wrote:
>
> What's the best way to impose systematic number typing on existing untyped
> code, for instance, forcing everything to be a flonum? Does it require
> switching to Typed Racket? Or does mean making explicit calls to
> `exact->in
>
> Here's what I'd do: decide on a smallest fractional point and a longest
> length, and determine how many bits that requires. If 52 bits is enough,
> use flonums. If it's not, write a prototype using bigfloats. If that's too
> slow, try double-doubles or fixed-point numbers.
What's the best wa
That's helpful, thanks.
I was considering either 64-bit flonum millimeters or 64-bit fixnum
nanometers. If there's not a meaningful speed advantage, I'll go with
flonum millimeters, because they're more readable and thinkable.
Points are traditional in typesetting systems, but that's a habit wort
Here are some options for representing lengths.
* Fixed-point numbers; i.e. a fixnum n represents n/2^k (where k = 16
for TeX). These are cheap and easy until you want to multiply or divide
them. Then they get more expensive and bit-shifty. You can forget about
doing anything else quickly. On
Right, I meant "exact" in the Racket sense of "exact rational."
The broader issue I'm thinking about is what kind of units to use in a
typesetting system in order to get the best balance of precision and speed.
For instance, the flexibility of a 64-bit flonum doesn't necessarily buy
you anything
We should probably improve the contracts on `racket/draw` to promise
flonum results for text metrics. The intent is to make metric-derived
calculations have a predictable cost, instead of potentially triggering
expensive exact arithmetic.
When you say that Pango produces "exact" results, do you me
The `get-text-extent` method in racket/draw does not contractually guarantee
either exact or inexact numbers, though in practice I find it produces inexact.
This function, however, calls into the Pango text-layout system. I find that
when I invoke Pango's text measuring directly through the FFI
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