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Fix function pointer syntax, booleans, return multivals

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This commit is contained in:
Jeremy Penner 2023-12-04 19:08:23 -05:00
parent 8e6a04536a
commit eafe21c6db
3 changed files with 58 additions and 34 deletions
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43
README.md
View file

@ -102,13 +102,14 @@ auto-convert `-` to `_` at least.
```
#### Function pointers
Function pointer types are defined with the `->` form, which accepts two arguments - a sequence
of types representing the input parameter types, and a sequence of types representing the return
value. Actually this kind of sucks, I think we should use the same syntax as `def`. I'll probably
change this. But this is how it works right now:
Function pointer types are defined with the `->` form, which a variable number of types as arguments.
Similar to `def`, you can put a `:` in your argument list to delineate between input parameters and
output types. Unlike `def`, if no `:` is present it is assumed that the function does not return a value,
as inference is not possible.
```fennel
(local callback (ttype (-> [[int] int] [int]))) ; compiles to: local callback = { &int, int } -> { int }
(local callback (ttype (-> [int] int : int))) ; compiles to: local callback = { &int, int } -> { int }
(local callback (ttype (-> float))) ; compiles to: local callback = { float } -> {}
```
#### Tuples
@ -135,17 +136,6 @@ it consistently mean "create a quote" everywhere. Not sure.)
### Terra syntax
#### Pointers and arrays
Dereferencing a pointer or accessing an element in an array uses the same syntax as defining a pointer
or array type - the Fennel sequence literal. To take a reference to a value, you can use the `&` form.
```fennel
(def [ptr [int]] (return [ptr])) ; compiles to: terra (ptr : &int) return @ptr end
(def [arr [int 8]] (return [arr 5])) ; compiles to: terra (arr : int[8]) return arr[5] end
(def [nested [[int]]] (return [nested 0 3])) ; compiles to: terra (nested : &&int) return nested[0][3] end
(def [ptr [int] : [int]] (return (& [ptr 1]))) ; compiles to: terra (ptr : &int): &int return &ptr[1] end
```
#### var
```fennel
(var name initial-value) ; compiles to: var name = initial-value
@ -162,6 +152,18 @@ syntax for _not_ initalizing the variable on declaration.
(tset struct (getfield) value) ; compiles to: struct.[getfield()] = value
```
#### Pointers and arrays
Dereferencing a pointer or accessing an element in an array uses the same syntax as defining a pointer
or array type - the Fennel sequence literal. To take a reference to a value, you can use the `&` form.
```fennel
(def [ptr [int]] (return [ptr])) ; compiles to: terra (ptr : &int) return @ptr end
(def [arr [int 8]] (return [arr 5])) ; compiles to: terra (arr : int[8]) return arr[5] end
(def [nested [[int]]] (return [nested 0 3])) ; compiles to: terra (nested : &&int) return nested[0][3] end
(def [nested [[int]]] (return [[nested] 3])) ; compiles to: terra (nested : &&int) return (@nested)[3] end
(def [ptr [int] : [int]] (return (& [ptr 1]))) ; compiles to: terra (ptr : &int): &int return &ptr[1] end
```
#### field access
```fennel
struct.field ; compiles to: struct.field
@ -229,4 +231,13 @@ type.
| `(<< x y)` | `x << y` | arithmetic shift x left by y bits |
| `(>> x y)` | `x >> y` | arithmetic shift x right by y bits |
#### return
Terra functions can return multiple values, or none. Returns must be explicitly
written with the `return` form.
```fennel
(def [: int] (return 5)) ; compiles to: terra (): { int } return 5 end
(def [: float float] (return -1.5 1.5)) ; compiles to: terra (): { float float } return -1.5, 1.5 end
```
#### Fennel escaping

4
go.fnl
View file

@ -16,3 +16,7 @@
(print result result.real result.imag (get-real result))
(set-real result 10)
(print (get-real result)))
(print (unterra
(def [: int bool] (return 5 true))
))

41
terra.fnl
View file

@ -59,7 +59,7 @@
result)
:expr (fn [self expr]
(if (and (sym? expr) (not (multi-sym? expr))) (self:env-ref expr)
(= (type expr) :number) (tostring expr)
(or (= (type expr) :number) (= (type expr) :boolean)) (tostring expr)
(= expr nil) :nil
(let [name (safesym :inline-expr)
arglist (sequence)
@ -113,7 +113,7 @@
(where symbol (sym? symbol))
(scope:reference symbol)
(where lit (or (= (type lit) :string) (= (type lit) :number) (= (type lit) :nil)))
(where lit (or (= (type lit) :string) (= (type lit) :number) (= (type lit) :nil) (= (type lit) :boolean)))
(scope:expr lit)
_ (error (.. "Failed to parse expression: " (view form)))))
@ -152,13 +152,29 @@
_ (error (.. "Invalid field name: " (view name)))))
(fn find-ival [tbl pred]
(var ival nil)
(each [i val (ipairs tbl)]
(when (pred val) (set ival i)))
ival)
(fn split-arglist [arglist]
(let [iarg-return-sep (find-ival arglist #(and (sym? $1) (= (tostring $1) ":")))
in (icollect [i arg (ipairs arglist) &until (= i iarg-return-sep)] arg)
out (when (not= iarg-return-sep nil) (icollect [i arg (ipairs arglist)] (when (> i iarg-return-sep) arg)))]
(values in out)))
(fn arglist-type [arglist scope] (.. "{ " (commasep (or arglist []) #(comp.type $1 scope)) " }"))
(tset type-constructors :-> (fn [[in out] scope] (.. (arglist-type in scope) " -> " (arglist-type out scope))))
(tset type-constructors :-> (fn [argtyps scope]
(let [(in out) (split-arglist argtyps)]
(.. (arglist-type in scope) " -> " (arglist-type (or out []) scope)))))
(tset type-constructors :& (fn [[typ] scope] (.. :& (comp.type typ scope))))
(tset type-constructors :$ (fn [typs scope] (.. "tuple(" (commasep typs #(comp.type $1 scope)) ")")))
(fn type-constructors.unquote [[expr] scope] (scope:expr expr))
(fn forms.rawterra [[text] scope] text)
(fn forms.raw-escape [[text] scope] text)
(fn type-constructors.raw-escape [[text] scope] text)
(fn forms.var [defn scope]
(case defn
[name typ initval] (.. "var " (scope:addlocal name) " : " (comp.type typ scope) " = " (comp.expr initval scope))
@ -167,22 +183,15 @@
(fn forms.do [stmts scope]
(scope:with #(block :do stmts :end scope #(comp.expr $1 scope))))
(fn find-ival [tbl pred]
(var ival nil)
(each [i val (ipairs tbl)]
(when (pred val) (set ival i)))
ival)
(fn forms.def [[arglist & stmts] scope]
(scope:with #(let [iarg-return-sep (find-ival arglist #(and (sym? $1) (= (tostring $1) ":")))
argpairs (fcollect [i 1 (length arglist) 2 &until (= i iarg-return-sep)]
{:name (. arglist i) :type (. arglist (+ i 1))})
rettyps (when iarg-return-sep (icollect [i typ (ipairs arglist)] (when (> i iarg-return-sep) typ)))
rettyp (if rettyps (.. ": { " (commasep rettyps #(comp.type $1 scope)) " }") "")
(scope:with #(let [(in out) (split-arglist arglist)
argpairs (fcollect [i 1 (length in) 2] {:name (. in i) :type (. in (+ i 1))})
rettyp (if out (.. ": { " (commasep out #(comp.type $1 scope)) " }") "")
argdefs (commasep argpairs #(.. (scope:addlocal $1.name) " : " (comp.type $1.type scope)))]
(block (.. "terra (" argdefs ")" rettyp) stmts :end scope #(comp.expr $1 scope)))))
(fn forms.return [[expr] scope] (.. "return " (comp.expr expr scope)))
(fn forms.return [vals scope] (.. "return " (commasep vals #(comp.expr $1 scope))))
(fn forms.cast [[typ expr] scope]
(.. "([" (comp.type typ scope)"](" (comp.expr expr scope) "))"))
(fn forms.unquote [[expr] scope] (.. "([" (scope:expr expr) "])"))