2016-09-12 02:10:59 +00:00
//: For convenience, allow Mu types to be abbreviated.
2016-08-31 22:53:25 +00:00
2016-09-12 01:43:38 +00:00
: ( scenarios transform )
2016-09-12 00:14:48 +00:00
: ( scenario type_abbreviations )
type foo = number
3309
Rip out everything to fix one failing unit test (commit 3290; type
abbreviations).
This commit does several things at once that I couldn't come up with a
clean way to unpack:
A. It moves to a new representation for type trees without changing
the actual definition of the `type_tree` struct.
B. It adds unit tests for our type metadata precomputation, so that
errors there show up early and in a simpler setting rather than dying
when we try to load Mu code.
C. It fixes a bug, guarding against infinite loops when precomputing
metadata for recursive shape-shifting containers. To do this it uses a
dumb way of comparing type_trees, comparing their string
representations instead. That is likely incredibly inefficient.
Perhaps due to C, this commit has made Mu incredibly slow. Running all
tests for the core and the edit/ app now takes 6.5 minutes rather than
3.5 minutes.
== more notes and details
I've been struggling for the past week now to back out of a bad design
decision, a premature optimization from the early days: storing atoms
directly in the 'value' slot of a cons cell rather than creating a
special 'atom' cons cell and storing it on the 'left' slot. In other
words, if a cons cell looks like this:
o
/ | \
left val right
..then the type_tree (a b c) used to look like this (before this
commit):
o
| \
a o
| \
b o
| \
c null
..rather than like this 'classic' approach to s-expressions which never
mixes val and right (which is what we now have):
o
/ \
o o
| / \
a o o
| / \
b o null
|
c
The old approach made several operations more complicated, most recently
the act of replacing a (possibly atom/leaf) sub-tree with another. That
was the final straw that got me to realize the contortions I was going
through to save a few type_tree nodes (cons cells).
Switching to the new approach was hard partly because I've been using
the old approach for so long and type_tree manipulations had pervaded
everything. Another issue I ran into was the realization that my layers
were not cleanly separated. Key parts of early layers (precomputing type
metadata) existed purely for far later ones (shape-shifting types).
Layers I got repeatedly stuck at:
1. the transform for precomputing type sizes (layer 30)
2. type-checks on merge instructions (layer 31)
3. the transform for precomputing address offsets in types (layer 36)
4. replace operations in supporting shape-shifting recipes (layer 55)
After much thrashing I finally noticed that it wasn't the entirety of
these layers that was giving me trouble, but just the type metadata
precomputation, which had bugs that weren't manifesting until 30 layers
later. Or, worse, when loading .mu files before any tests had had a
chance to run. A common failure mode was running into types at run time
that I hadn't precomputed metadata for at transform time.
Digging into these bugs got me to realize that what I had before wasn't
really very good, but a half-assed heuristic approach that did a whole
lot of extra work precomputing metadata for utterly meaningless types
like `((address number) 3)` which just happened to be part of a larger
type like `(array (address number) 3)`.
So, I redid it all. I switched the representation of types (because the
old representation made unit tests difficult to retrofit) and added unit
tests to the metadata precomputation. I also made layer 30 only do the
minimal metadata precomputation it needs for the concepts introduced
until then. In the process, I also made the precomputation more correct
than before, and added hooks in the right place so that I could augment
the logic when I introduced shape-shifting containers.
== lessons learned
There's several levels of hygiene when it comes to layers:
1. Every layer introduces precisely what it needs and in the simplest
way possible. If I was building an app until just that layer, nothing
would seem over-engineered.
2. Some layers are fore-shadowing features in future layers. Sometimes
this is ok. For example, layer 10 foreshadows containers and arrays and
so on without actually supporting them. That is a net win because it
lets me lay out the core of Mu's data structures out in one place. But
if the fore-shadowing gets too complex things get nasty. Not least
because it can be hard to write unit tests for features before you
provide the plumbing to visualize and manipulate them.
3. A layer is introducing features that are tested only in later layers.
4. A layer is introducing features with tests that are invalidated in
later layers. (This I knew from early on to be an obviously horrendous
idea.)
Summary: avoid Level 2 (foreshadowing layers) as much as possible.
Tolerate it indefinitely for small things where the code stays simple
over time, but become strict again when things start to get more
complex.
Level 3 is mostly a net lose, but sometimes it can be expedient (a real
case of the usually grossly over-applied term "technical debt"), and
it's better than the conventional baseline of no layers and no
scenarios. Just clean it up as soon as possible.
Definitely avoid layer 4 at any time.
== minor lessons
Avoid unit tests for trivial things, write scenarios in context as much as
possible. But within those margins unit tests are fine. Just introduce them
before any scenarios (commit 3297).
Reorganizing layers can be easy. Just merge layers for starters! Punt on
resplitting them in some new way until you've gotten them to work. This is the
wisdom of Refactoring: small steps.
What made it hard was not wanting to merge *everything* between layer 30
and 55. The eventual insight was realizing I just need to move those two
full-strength transforms and nothing else.
2016-09-10 01:32:52 +00:00
def main [
2016-09-12 00:14:48 +00:00
a : foo < - copy 34
3309
Rip out everything to fix one failing unit test (commit 3290; type
abbreviations).
This commit does several things at once that I couldn't come up with a
clean way to unpack:
A. It moves to a new representation for type trees without changing
the actual definition of the `type_tree` struct.
B. It adds unit tests for our type metadata precomputation, so that
errors there show up early and in a simpler setting rather than dying
when we try to load Mu code.
C. It fixes a bug, guarding against infinite loops when precomputing
metadata for recursive shape-shifting containers. To do this it uses a
dumb way of comparing type_trees, comparing their string
representations instead. That is likely incredibly inefficient.
Perhaps due to C, this commit has made Mu incredibly slow. Running all
tests for the core and the edit/ app now takes 6.5 minutes rather than
3.5 minutes.
== more notes and details
I've been struggling for the past week now to back out of a bad design
decision, a premature optimization from the early days: storing atoms
directly in the 'value' slot of a cons cell rather than creating a
special 'atom' cons cell and storing it on the 'left' slot. In other
words, if a cons cell looks like this:
o
/ | \
left val right
..then the type_tree (a b c) used to look like this (before this
commit):
o
| \
a o
| \
b o
| \
c null
..rather than like this 'classic' approach to s-expressions which never
mixes val and right (which is what we now have):
o
/ \
o o
| / \
a o o
| / \
b o null
|
c
The old approach made several operations more complicated, most recently
the act of replacing a (possibly atom/leaf) sub-tree with another. That
was the final straw that got me to realize the contortions I was going
through to save a few type_tree nodes (cons cells).
Switching to the new approach was hard partly because I've been using
the old approach for so long and type_tree manipulations had pervaded
everything. Another issue I ran into was the realization that my layers
were not cleanly separated. Key parts of early layers (precomputing type
metadata) existed purely for far later ones (shape-shifting types).
Layers I got repeatedly stuck at:
1. the transform for precomputing type sizes (layer 30)
2. type-checks on merge instructions (layer 31)
3. the transform for precomputing address offsets in types (layer 36)
4. replace operations in supporting shape-shifting recipes (layer 55)
After much thrashing I finally noticed that it wasn't the entirety of
these layers that was giving me trouble, but just the type metadata
precomputation, which had bugs that weren't manifesting until 30 layers
later. Or, worse, when loading .mu files before any tests had had a
chance to run. A common failure mode was running into types at run time
that I hadn't precomputed metadata for at transform time.
Digging into these bugs got me to realize that what I had before wasn't
really very good, but a half-assed heuristic approach that did a whole
lot of extra work precomputing metadata for utterly meaningless types
like `((address number) 3)` which just happened to be part of a larger
type like `(array (address number) 3)`.
So, I redid it all. I switched the representation of types (because the
old representation made unit tests difficult to retrofit) and added unit
tests to the metadata precomputation. I also made layer 30 only do the
minimal metadata precomputation it needs for the concepts introduced
until then. In the process, I also made the precomputation more correct
than before, and added hooks in the right place so that I could augment
the logic when I introduced shape-shifting containers.
== lessons learned
There's several levels of hygiene when it comes to layers:
1. Every layer introduces precisely what it needs and in the simplest
way possible. If I was building an app until just that layer, nothing
would seem over-engineered.
2. Some layers are fore-shadowing features in future layers. Sometimes
this is ok. For example, layer 10 foreshadows containers and arrays and
so on without actually supporting them. That is a net win because it
lets me lay out the core of Mu's data structures out in one place. But
if the fore-shadowing gets too complex things get nasty. Not least
because it can be hard to write unit tests for features before you
provide the plumbing to visualize and manipulate them.
3. A layer is introducing features that are tested only in later layers.
4. A layer is introducing features with tests that are invalidated in
later layers. (This I knew from early on to be an obviously horrendous
idea.)
Summary: avoid Level 2 (foreshadowing layers) as much as possible.
Tolerate it indefinitely for small things where the code stays simple
over time, but become strict again when things start to get more
complex.
Level 3 is mostly a net lose, but sometimes it can be expedient (a real
case of the usually grossly over-applied term "technical debt"), and
it's better than the conventional baseline of no layers and no
scenarios. Just clean it up as soon as possible.
Definitely avoid layer 4 at any time.
== minor lessons
Avoid unit tests for trivial things, write scenarios in context as much as
possible. But within those margins unit tests are fine. Just introduce them
before any scenarios (commit 3297).
Reorganizing layers can be easy. Just merge layers for starters! Punt on
resplitting them in some new way until you've gotten them to work. This is the
wisdom of Refactoring: small steps.
What made it hard was not wanting to merge *everything* between layer 30
and 55. The eventual insight was realizing I just need to move those two
full-strength transforms and nothing else.
2016-09-10 01:32:52 +00:00
]
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+ transform : product type after expanding abbreviations : " number "
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: ( before " End Globals " )
map < string , type_tree * > Type_abbreviations , Type_abbreviations_snapshot ;
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//:: Defining type abbreviations.
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: ( before " End Command Handlers " )
else if ( command = = " type " ) {
load_type_abbreviations ( in ) ;
}
: ( code )
void load_type_abbreviations ( istream & in ) {
string new_type_name = next_word ( in ) ;
assert ( has_data ( in ) | | ! new_type_name . empty ( ) ) ;
if ( ! has_data ( in ) | | new_type_name . empty ( ) ) {
raise < < " incomplete 'type' statement; must be of the form 'type <new type name> = <type expression>' \n " < < end ( ) ;
return ;
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}
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string arrow = next_word ( in ) ;
assert ( has_data ( in ) | | ! arrow . empty ( ) ) ;
if ( arrow . empty ( ) ) {
raise < < " incomplete 'type' statement 'type " < < new_type_name < < " ' \n " < < end ( ) ;
return ;
}
if ( arrow ! = " = " ) {
raise < < " 'type' statements must be of the form 'type <new type name> = <type expression>' but got 'type " < < new_type_name < < ' ' < < arrow < < " ' \n " < < end ( ) ;
return ;
}
if ( ! has_data ( in ) ) {
raise < < " incomplete 'type' statement 'type " < < new_type_name < < " =' \n " < < end ( ) ;
return ;
}
string old = next_word ( in ) ;
if ( old . empty ( ) ) {
raise < < " incomplete 'type' statement 'type " < < new_type_name < < " =' \n " < < end ( ) ;
raise < < " 'type' statements must be of the form 'type <new type name> = <type expression>' but got 'type " < < new_type_name < < ' ' < < arrow < < " ' \n " < < end ( ) ;
return ;
}
if ( contains_key ( Type_abbreviations , new_type_name ) ) {
raise < < " 'type' conflict: ' " < < new_type_name < < " ' defined as both ' " < < names_to_string_without_quotes ( get ( Type_abbreviations , new_type_name ) ) < < " ' and ' " < < old < < " ' \n " < < end ( ) ;
return ;
}
trace ( 9990 , " type " ) < < " alias " < < new_type_name < < " = " < < old < < end ( ) ;
type_tree * old_type = new_type_tree ( old ) ;
put ( Type_abbreviations , new_type_name , old_type ) ;
}
type_tree * new_type_tree ( const string & x ) {
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string_tree * type_names = starts_with ( x , " ( " ) ? parse_string_tree ( x ) : parse_string_list ( x ) ;
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type_tree * result = new_type_tree ( type_names ) ;
delete type_names ;
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expand_type_abbreviations ( result ) ;
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return result ;
}
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string_tree * parse_string_list ( const string & s ) {
istringstream in ( s ) ;
in > > std : : noskipws ;
return parse_property_list ( in ) ;
}
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: ( scenario type_error1 )
% Hide_errors = true ;
type foo
+ error : incomplete ' type ' statement ' type foo '
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: ( scenario type_error2 )
% Hide_errors = true ;
type foo =
+ error : incomplete ' type ' statement ' type foo = '
: ( scenario type_error3 )
% Hide_errors = true ;
type foo bar baz
+ error : ' type ' statements must be of the form ' type < new type name > = < type expression > ' but got ' type foo bar '
: ( scenario type_conflict_error )
% Hide_errors = true ;
type foo = bar
type foo = baz
+ error : ' type ' conflict : ' foo ' defined as both ' bar ' and ' baz '
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: ( scenario type_abbreviation_for_compound )
type foo = address : number
def main [
1 : foo < - copy null
]
+ transform : product type after expanding abbreviations : ( " address " " number " )
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//: cleaning up type abbreviations between tests and before exiting
: ( before " End save_snapshots " )
Type_abbreviations_snapshot = Type_abbreviations ;
: ( before " End restore_snapshots " )
restore_type_abbreviations ( ) ;
: ( before " End One-time Setup " )
atexit ( clear_type_abbreviations ) ;
: ( code )
void restore_type_abbreviations ( ) {
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for ( map < string , type_tree * > : : iterator p = Type_abbreviations . begin ( ) ; p ! = Type_abbreviations . end ( ) ; + + p ) {
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if ( ! contains_key ( Type_abbreviations_snapshot , p - > first ) )
delete p - > second ;
}
Type_abbreviations . clear ( ) ;
Type_abbreviations = Type_abbreviations_snapshot ;
}
void clear_type_abbreviations ( ) {
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for ( map < string , type_tree * > : : iterator p = Type_abbreviations . begin ( ) ; p ! = Type_abbreviations . end ( ) ; + + p )
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delete p - > second ;
Type_abbreviations . clear ( ) ;
}
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//:: A few default abbreviations.
: ( before " End Mu Types Initialization " )
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put ( Type_abbreviations , " & " , new_type_tree ( " address " ) ) ;
put ( Type_abbreviations , " @ " , new_type_tree ( " array " ) ) ;
put ( Type_abbreviations , " num " , new_type_tree ( " number " ) ) ;
put ( Type_abbreviations , " bool " , new_type_tree ( " boolean " ) ) ;
put ( Type_abbreviations , " char " , new_type_tree ( " character " ) ) ;
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: ( scenario use_type_abbreviations_when_declaring_type_abbreviations )
type foo = & : num
def main [
1 : foo < - copy null
]
+ transform : product type after expanding abbreviations : ( " address " " number " )
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//:: Expand type aliases before running.
//: We'll do this in a transform so that we don't need to define abbreviations
//: before we use them.
: ( scenario abbreviations_for_address_and_array )
def main [
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f 1 : & : num # abbreviation for ' address : number '
f 2 : @ : num # abbreviation for ' array : number '
f 3 : & : @ : num # combining ' & ' and ' @ '
f 4 : & : & : @ : & : @ : num # . . any number of times
f { 5 : ( array ( & num ) 3 ) } # support for dilated reagents and more complex parse trees
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]
def f [
]
+ transform : - - - expand type abbreviations in recipe ' main '
+ transform : ingredient type after expanding abbreviations : ( " address " " number " )
+ transform : ingredient type after expanding abbreviations : ( " array " " number " )
+ transform : ingredient type after expanding abbreviations : ( " address " " array " " number " )
+ transform : ingredient type after expanding abbreviations : ( " address " " address " " array " " address " " array " " number " )
+ transform : ingredient type after expanding abbreviations : ( " array " ( " address " " number " ) " 3 " )
: ( before " Transform.push_back(update_instruction_operations) " )
Transform . push_back ( expand_type_abbreviations ) ; // idempotent
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// Begin Type Modifying Transforms
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// End Type Modifying Transforms
: ( code )
void expand_type_abbreviations ( const recipe_ordinal r ) {
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expand_type_abbreviations ( get ( Recipe , r ) ) ;
}
void expand_type_abbreviations ( const recipe & caller ) {
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trace ( 9991 , " transform " ) < < " --- expand type abbreviations in recipe ' " < < caller . name < < " ' " < < end ( ) ;
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for ( int i = 0 ; i < SIZE ( caller . steps ) ; + + i ) {
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const instruction & inst = caller . steps . at ( i ) ;
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trace ( 9991 , " transform " ) < < " instruction ' " < < to_original_string ( inst ) < < end ( ) ;
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for ( long int i = 0 ; i < SIZE ( inst . ingredients ) ; + + i ) {
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expand_type_abbreviations ( inst . ingredients . at ( i ) . type ) ;
trace ( 9992 , " transform " ) < < " ingredient type after expanding abbreviations: " < < names_to_string ( inst . ingredients . at ( i ) . type ) < < end ( ) ;
}
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for ( long int i = 0 ; i < SIZE ( inst . products ) ; + + i ) {
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expand_type_abbreviations ( inst . products . at ( i ) . type ) ;
trace ( 9992 , " transform " ) < < " product type after expanding abbreviations: " < < names_to_string ( inst . products . at ( i ) . type ) < < end ( ) ;
}
}
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// End Expand Type Abbreviations(caller)
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}
void expand_type_abbreviations ( type_tree * type ) {
if ( ! type ) return ;
if ( ! type - > atom ) {
expand_type_abbreviations ( type - > left ) ;
expand_type_abbreviations ( type - > right ) ;
return ;
}
if ( contains_key ( Type_abbreviations , type - > name ) )
* type = type_tree ( * get ( Type_abbreviations , type - > name ) ) ;
}
