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lang: Add function values and lambdas

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This adds a giant missing piece of the language: proper function values!
It is lovely to now understand why early programming language designers
didn't implement these, but a joy to now reap the benefits of them. In
adding these, many other changes had to be made to get them to "fit"
correctly. This improved the code and fixed a number of bugs.
Unfortunately this touched many areas of the code, and since I was
learning how to do all of this for the first time, I've squashed most of
my work into a single commit. Some more information:

* This adds over 70 new tests to verify the new functionality.

* Functions, global variables, and classes can all be implemented
natively in mcl and built into core packages.

* A new compiler step called "Ordering" was added. It is called by the
SetScope step, and determines statement ordering and shadowing
precedence formally. It helped remove at least one bug and provided the
additional analysis required to properly capture variables when
implementing function generators and closures.

* The type unification code was improved to handle the new cases.

* Light copying of Node's allowed our function graphs to be more optimal
and share common vertices and edges. For example, if two different
closures capture a variable $x, they'll both use the same copy when
running the function, since the compiler can prove if they're identical.

* Some areas still need improvements, but this is ready for mainstream
testing and use!
This commit is contained in:
James Shubin
2019-06-04 21:51:21 -04:00
parent 4f1c463bdd
commit f53376cea1
189 changed files with 7170 additions and 849 deletions
Download Patch File Download Diff File Expand all files Collapse all files

126
lang/funcs/simplepoly/simplepoly.go
View File

@@ -27,6 +27,13 @@ import (
"github.com/purpleidea/mgmt/util/errwrap"
)
const (
// DirectInterface specifies whether we should use the direct function
// API or not. If we don't use it, then these simple functions are
// wrapped with the struct below.
DirectInterface = false // XXX: fix any bugs and set to true!
)
// RegisteredFuncs maps a function name to the corresponding static, pure funcs.
var RegisteredFuncs = make(map[string][]*types.FuncValue) // must initialize
@@ -60,10 +67,15 @@ func Register(name string, fns []*types.FuncValue) {
panic(fmt.Sprintf("polyfunc %s has a duplicate implementation: %+v", name, err))
}
_, err := consistentArgs(fns)
if err != nil {
panic(fmt.Sprintf("polyfunc %s has inconsistent arg names: %+v", name, err))
}
RegisteredFuncs[name] = fns // store a copy for ourselves
// register a copy in the main function database
funcs.Register(name, func() interfaces.Func { return &simplePolyFunc{Fns: fns} })
funcs.Register(name, func() interfaces.Func { return &WrappedFunc{Fns: fns} })
}
// ModuleRegister is exactly like Register, except that it registers within a
@@ -72,10 +84,38 @@ func ModuleRegister(module, name string, fns []*types.FuncValue) {
Register(module+funcs.ModuleSep+name, fns)
}
// simplePolyFunc is a scaffolding function struct which fulfills the
// boiler-plate for the function API, but that can run a very simple, static,
// pure, polymorphic function.
type simplePolyFunc struct {
// consistentArgs returns the list of arg names across all the functions or
// errors if one consistent list could not be found.
func consistentArgs(fns []*types.FuncValue) ([]string, error) {
if len(fns) == 0 {
return nil, fmt.Errorf("no functions specified for simple polyfunc")
}
seq := []string{}
for _, x := range fns {
typ := x.Type()
if typ.Kind != types.KindFunc {
return nil, fmt.Errorf("expected %s, got %s", types.KindFunc, typ.Kind)
}
ord := typ.Ord
// check
l := len(seq)
if m := len(ord); m < l {
l = m // min
}
for i := 0; i < l; i++ { // check shorter list
if seq[i] != ord[i] {
return nil, fmt.Errorf("arg name at index %d differs (%s != %s)", i, seq[i], ord[i])
}
}
seq = ord // keep longer version!
}
return seq, nil
}
// WrappedFunc is a scaffolding function struct which fulfills the boiler-plate
// for the function API, but that can run a very simple, static, pure,
// polymorphic function.
type WrappedFunc struct {
Fns []*types.FuncValue // list of possible functions
fn *types.FuncValue // the concrete version of our chosen function
@@ -88,10 +128,22 @@ type simplePolyFunc struct {
closeChan chan struct{}
}
// ArgGen returns the Nth arg name for this function.
func (obj *WrappedFunc) ArgGen(index int) (string, error) {
seq, err := consistentArgs(obj.Fns)
if err != nil {
return "", err
}
if l := len(seq); index >= l {
return "", fmt.Errorf("index %d exceeds arg length of %d", index, l)
}
return seq[index], nil
}
// Polymorphisms returns the list of possible function signatures available for
// this static polymorphic function. It relies on type and value hints to limit
// the number of returned possibilities.
func (obj *simplePolyFunc) Polymorphisms(partialType *types.Type, partialValues []types.Value) ([]*types.Type, error) {
func (obj *WrappedFunc) Polymorphisms(partialType *types.Type, partialValues []types.Value) ([]*types.Type, error) {
if len(obj.Fns) == 0 {
return nil, fmt.Errorf("no matching signatures for simple polyfunc")
}
@@ -101,7 +153,7 @@ func (obj *simplePolyFunc) Polymorphisms(partialType *types.Type, partialValues
for _, f := range obj.Fns {
// TODO: if status is "both", should we skip as too difficult?
_, err := f.T.ComplexCmp(partialType)
// XXX: can an f.T with a variant compare with a partial ?
// can an f.T with a variant compare with a partial ? (yes)
if err != nil {
continue
}
@@ -115,58 +167,28 @@ func (obj *simplePolyFunc) Polymorphisms(partialType *types.Type, partialValues
// specific statically typed version. It is usually run after Unify completes,
// and must be run before Info() and any of the other Func interface methods are
// used.
func (obj *simplePolyFunc) Build(typ *types.Type) error {
func (obj *WrappedFunc) Build(typ *types.Type) error {
// typ is the KindFunc signature we're trying to build...
if typ.Out == nil {
return fmt.Errorf("return type of function must be specified")
}
// find typ in obj.Fns
for ix, f := range obj.Fns {
if f.T.HasVariant() {
continue // match these if no direct matches exist
}
// FIXME: can we replace this by the complex matcher down below?
if f.T.Cmp(typ) == nil {
obj.buildFunction(typ, ix) // found match at this index
return nil
}
index, err := langutil.FnMatch(typ, obj.Fns)
if err != nil {
return err
}
obj.buildFunction(typ, index) // found match at this index
// match concrete type against our list that might contain a variant
var found bool
for ix, f := range obj.Fns {
_, err := typ.ComplexCmp(f.T)
if err != nil {
continue
}
if found { // already found one...
// TODO: we *could* check that the previous duplicate is
// equivalent, but in this case, it is really a bug that
// the function author had by allowing ambiguity in this
return fmt.Errorf("duplicate match found for build type: %+v", typ)
}
found = true
obj.buildFunction(typ, ix) // found match at this index
}
// ensure there's only one match...
if found {
return nil // w00t!
}
return fmt.Errorf("unable to find a compatible function for type: %+v", typ)
return nil
}
// buildFunction builds our concrete static function, from the potentially
// abstract, possibly variant containing list of functions.
func (obj *simplePolyFunc) buildFunction(typ *types.Type, ix int) {
func (obj *WrappedFunc) buildFunction(typ *types.Type, ix int) {
obj.fn = obj.Fns[ix].Copy().(*types.FuncValue)
obj.fn.T = typ.Copy() // overwrites any contained "variant" type
}
// Validate makes sure we've built our struct properly. It is usually unused for
// normal functions that users can use directly.
func (obj *simplePolyFunc) Validate() error {
func (obj *WrappedFunc) Validate() error {
if len(obj.Fns) == 0 {
return fmt.Errorf("missing list of functions")
}
@@ -195,24 +217,28 @@ func (obj *simplePolyFunc) Validate() error {
}
// Info returns some static info about itself.
func (obj *simplePolyFunc) Info() *interfaces.Info {
func (obj *WrappedFunc) Info() *interfaces.Info {
var sig *types.Type
if obj.fn != nil { // don't panic if called speculatively
sig = obj.fn.Type()
}
return &interfaces.Info{
Pure: true,
Memo: false, // TODO: should this be something we specify here?
Sig: obj.fn.Type(),
Sig: sig,
Err: obj.Validate(),
}
}
// Init runs some startup code for this function.
func (obj *simplePolyFunc) Init(init *interfaces.Init) error {
func (obj *WrappedFunc) Init(init *interfaces.Init) error {
obj.init = init
obj.closeChan = make(chan struct{})
return nil
}
// Stream returns the changing values that this func has over time.
func (obj *simplePolyFunc) Stream() error {
func (obj *WrappedFunc) Stream() error {
defer close(obj.init.Output) // the sender closes
for {
select {
@@ -275,7 +301,7 @@ func (obj *simplePolyFunc) Stream() error {
}
// Close runs some shutdown code for this function and turns off the stream.
func (obj *simplePolyFunc) Close() error {
func (obj *WrappedFunc) Close() error {
close(obj.closeChan)
return nil
}