In some cases, 0 results will be represented by a NULL results-array
pointer. Fix the interpreter to detect a single result completion
through a count of 1 instead of a NULL result-array pointer.
Also, remove a bug extra push operation in the JIT-generated code for
`begin0`. (Other features of the JIT-generated code compensated for
the extra push in cases where the bytecode compiler did't optimize
away the `begin0`, so it turns out not to have caused a problem, but
that's a surprising and fragile set of coincidences.)
Closes#2571
order (like it does with the argument and result contracts), but ensuring
that the pre and post conditions come before the arguments (if possible)
closes#2560
so that it collects the pre/post conditions into sorted order with the
arguments (based on the dependencies), but then discards that
information and always evaluates the pre and post conditions after the
argument/result contract checks
improve accuracy of tanh function
using the implementation of https://www.math.utah.edu/~beebe/software/ieee/tanh.pdf
by changing from (/ (- 1 exp2z) (+ 1 exp2z)) to (- 1 (/ 2 (+ 1 exp2z)) the accuracy after rounding is increased (I was comparing with bftanh) and removes the fluctuations around z=18.35
using the polynomial for z ϵ(1.290e-8 to 0.549) seems to increase the accuracy after rounding even further
see comparison: http://pasterack.org/pastes/48436
especially the fact that (< (tanh 18.36)(tanh 18.37)) ;=> #t was tripping me up
the two extra conditions (z . < . 1.29e-8) and (z . < . 0.549) are optional to solve this
- Propagate disappeared uses from any pattern stx, not only those
attached to forms that themselves have a disappearing use.
- Fix for new local-apply-transformer handling of scopes.
This commit fixes an issue with the fix for contracted bindings in
signatures implemented in commit 5fb75e9f82. While the previous fix
worked in simple cases, it introduced a problem: although signatures
that define contracted bindings were able to refer to other bindings
in the signature in the binding contracts, but anyone doing so was
at the mercy of the exporting unit’s definition order. For example,
given a signature
(define-signature a^
[(contracted
[ctc contract?]
[val ctc])])
then a unit exporting the signature would cause a
use-before-initialization error if its definition for val appeared above
its definition for ctc.
This limitation did not exist in the units implementation prior to the
introduction of the sets-of-scopes expander in Racket v6.3 (after which
contracted bindings were broken until the aforementioned fix in Racket
v7.2). However, the fact that they worked at all seems semi-accidental:
instead of properly indirecting references to signature bindings within
binding contracts, the contract expressions were simply placed in a
context in which the existing names were bound. However, this meant that
any export that renamed identifiers could cause problems, which the
implementation strategy taken in this commit handles just fine.
When the result of `syntax-make-delta-introducer` adds scopes,
it needs to carry along any shifts that might be relevant.
The new implementation risks adding lots of redundant shifts. In this
case, it might be worth spending extra effort at shift-transfer time
to check whether the shift is redundant.
Closes#2542
