feat: sequencing of expressions with newline to same indent (#11)

feat: sequencing of expressions with newline to same indent

  Also revised README to reflect greater emphasis on streams.
  Haskell code generation unsurprisingly required a fairly significant
  rework.

  Resolves #3.

Co-authored-by: Glen Whitney <glen@studioinfinity.org>
Reviewed-on: #11
Co-Authored-By: Glen Whitney <glen@nobody@nowhere.net>
Co-Committed-By: Glen Whitney <glen@nobody@nowhere.net>

README.md

@@ -8,9 +8,12 @@ dimensions.
 
 So I embarked on this project to see if I could produce as comfortable a
 language as possible to work in, given that I inevitably will be doing a
-bunch of coding. The language will be
-organized around (unary) ++f++unctions, (binary) ++o++perators, and
-(nullary) ++str++eams, hence the name "fostr".
+bunch of coding. The language will be centrally organized around the
+concept of "streams" (somewhat in the spirit of
+[streem](https://github.com/matz/streem) and/or
+[Orc](http://orc.csres.utexas.edu/index.shtml)). In fact all higher-type
+entities will be cast in terms of streams, or in slogan form, "++f++unctions
+and (binary) ++o++perators are ++str++eams" (hence the name "fostr").
 
 Other guiding principles:
 
@@ -24,11 +27,9 @@ Other guiding principles:
   the language design from the ground up, it can be kept both effective and
   natural.
 
-* Code uses functions all the time. So needless to say, functions should be
-  first-class entities that are exceptionally easy to create, pass around,
-  etc.
-
-* And true to the name, operators and streams should be just as easy to handle.
+* fostr code uses streams (and their specializations to functions and
+  operators) all the time, so they are first-class entities that are easy
+  to create, pass around, compose, etc.
 
 * Try to keep the constructs available as simple to reason about as possible,
   and practical to use. So side effects are OK, and it should be clear when

metaborg.yaml

@@ -19,6 +19,7 @@ language:
   sdf:
     pretty-print: fostr
     sdf2table: java
+    jsglr-version: layout-sensitive
     placeholder:
       prefix: "$"
   stratego:

syntax/fostr.sdf3

@@ -10,28 +10,34 @@ context-free start-symbols
 
 context-free sorts
 
-  Start Ex
+  Start LineSeq Line Ex
 
 context-free syntax
   
-  Start.TopLevel = prog:Ex {layout(offside prog)}
+  Start.TopLevel   = LineSeq
+
+  LineSeq          = <<ln:Ex>> {layout(offside ln)}
+  LineSeq.Sequence = sq:Ex+    {layout(align-list sq)}
+
+  Ex+         = Ex+ ln:Ex {layout(offside ln)}
 
   Ex.Int      = INT
-  Ex.Stdio    = <stdio>
-  Ex.Sum      = {Ex "+"}+
-  Ex.Receives = [[Ex] << [Ex]] {left}
-  Ex.Enters   = [[Ex] >> [Ex]] {left}
+  Ex.Stream   = <stream>
+  Ex.Sum      = [[Ex] +  [Ex]] {left}
+  Ex.Gets     = [[Ex] << [Ex]] {left}
+  Ex.To       = [[Ex] >> [Ex]] {left}
+
   Ex          = <(<Ex>)> {bracket}
 
 context-free priorities
 
-  Ex.Enters
+  Ex.To
   > Ex.Sum
-  > Ex.Receives,
+  > Ex.Gets,
 
   // prevent cycle: no singletons
-  Ex.Sum <0> .> {Ex "+"}+ = Ex,
+  LineSeq.Sequence <0> .> Ex+       = Ex,
 
-  // flat: no Sum immediately in Sum:
-  {Ex "+"}+ = Ex <0> .> Ex.Sum,
-  {Ex "+"}+ = {Ex "+"}+ "+" Ex <2> .> Ex.Sum
+  // flat: No LineSeq immediately in LineSeq
+  Ex+ = Ex <0>     .> LineSeq.Sequence,
+  Ex+ = Ex+ Ex <1> .> LineSeq.Sequence

tests/basic.spt

@@ -13,9 +13,9 @@ that writes the sum of the ASCII codes for 'H', 'W', and '!' to standard output:
 **/
 
 /** md */ test emit_sum [[
-stdio << 72 + 87 + 33
-]]/* **/ parse to TopLevel(Receives(Stdio(),
-                                    Sum([Int("72"), Int("87"), Int("33")])))
+stream << 72 + 87 + 33
+]]/* **/ parse to TopLevel(Gets(Stream(),
+                                Sum(Sum(Int("72"), Int("87")), Int("33"))))
 /** writes
 192**/
 
@@ -40,32 +40,27 @@ For example, this snippet generates the following Python:
   start: 'Stdio\s='
 !}
 ```
-(which writes "192" to standard output), or this non-idiomatic, inefficient, but
-working Javascript:
-```javascript
-{! ../tests/emit_sum.js extract:
-  start: '^}'
-!}
-```
-In either case, there's also a preamble defining Stdio that's generated.
-(Haskell code generation is also currently supported.)
+(which writes "192" to standard output); it also generates identical code in
+this simple example for
+Javascript, although it generates a different preamble defining Stdio in each
+case. (Haskell code generation is also currently supported.)
 
 ### Everything has a value
 
 As mentioned in the [Introduction](../README.md), everything in a fostr
 program (including the entire program itself) is an expression and has
-a value. So what's the value of that expression above? Well, `stdio` is our
+a value. So what's the value of that expression above? Well, appropriately
+enough, `stream` is our
 first example of a stream, and for convenience, the value of a stream
-receiving an item is just the stream back again. The `<<` operator is also
-left-associative, so that way we can chain insertions into a stream:
+receiving an item is (usually) just the stream back again. The `<<` operator
+is also left-associative, so that way we can chain insertions into a stream:
 ```fostr
 **/
 
 /** md */ test emit_twice [[
-stdio << 72 + 87 + 33 << 291
+stream << 72 + 87 + 33 << 291
 ]]/* **/ parse to TopLevel(
-  Receives(Receives(Stdio(), Sum([Int("72"), Int("87"), Int("33")])),
-           Int("291")))
+  Gets(Gets(Stream(), Sum(Sum(Int("72"), Int("87")), Int("33"))), Int("291")))
 /** writes
 192291**/
 
@@ -75,14 +70,14 @@ Running this program produces a nice palindromic output: "192291".
 
 And because sometimes you want to emphasize the value and propagate that
 instead of the stream, you can also write these expressions "the other way"
-with `>>`; both forms return the first argument:
+with `>>`; both forms return the first argument, so the following writes "824":
 ```fostr
 **/
 
 /** md */ test enters_twice [[
-(7 + 8 >> stdio + 9) >> stdio
+(7 + 8 >> stream + 9) >> stream
 ]]/* **/ parse to TopLevel(
-  Enters(Sum([Int("7"), Enters(Int("8"), Stdio()), Int("9")]), Stdio()))
+  To(Sum(Sum(Int("7"), To(Int("8"), Stream())), Int("9")), Stream()))
 /** writes
 824**/
 
@@ -97,12 +92,12 @@ lines are indented from the start of the initial line:
 **/
 
 /** md */ test receive_enter_break [[
-stdio <<
+stream <<
   7
-  + 8 >> stdio
+  + 8 >> stream
   + 9
 ]]/* **/ parse to TopLevel(
-  Receives(Stdio(), Sum([Int("7"), Enters(Int("8"), Stdio()), Int("9")])))
+  Gets(Stream(), Sum(Sum(Int("7"), To(Int("8"), Stream())), Int("9"))))
 /** writes
 824**/
 
@@ -113,19 +108,56 @@ stdio <<
 **/
 
 /** md */ test enter_receive_bad_break [[
-(7 + 8 >> stdio + 9)
->> (stdio << 9 + 2)
+(7 + 8 >> stream + 9)
+>> (stream << 9 + 2)
 ]] /* **/ parse fails
 
 /* Extra tests not in the tour */
 test enter_receive [[
-(7 + 8 >> stdio + 9) >> (stdio << 9 + 2)
+(7 + 8 >> stream + 9) >> (stream << 9 + 2)
 ]]/* **/ parse to TopLevel(
-  Enters(Sum([Int("7"),Enters(Int("8"),Stdio()),Int("9")]),
-         Receives(Stdio(),Sum([Int("9"),Int("2")]))))
+  To(Sum(Sum(Int("7"),To(Int("8"),Stream())),Int("9")),
+     Gets(Stream(),Sum(Int("9"),Int("2")))))
 /** writes
 81124**/
 
+/** md
+```
+
+Of course, fostr programs are not limited to one line; expressions on successive
+lines are evaluated in sequence. For example, the program
+```fostr
+**/
+
+/** md */ test emit_thrice [[
+  stream << 72 + 87
+  stream << 88
+    + 96
+  99 + 12 >>
+          stream
+]] /* **/ parse to TopLevel( Sequence(
+    [ Gets(Stream(), Sum(Int("72"), Int("87")))
+    , Gets(Stream(), Sum(Int("88"), Int("96")))
+    , Sum(Int("99"), To(Int("12"), Stream()))]))
+/** writes
+15918412**/
+
+/** md
+```
+
+will write 15918412. fostr enforces that successive expressions in sequence
+must line up at the left, i.e., the following will not parse:
+
+```fostr
+**/
+
+/** md */ test emit_thrice_bad_alignment [[
+  stream << 72 + 87
+stream << 88
+    + 96
+  99 + 12 >> stream
+]] /* **/ parse fails
+
 /** md
 ```
 **/

tests/emit_sum.fos

@@ -1 +1 @@
-stdio << 72 + 87 + 33
+stream << 72 + 87 + 33

tests/emit_thrice.fos

@@ -0,0 +1,5 @@
+  stream << 72 + 87
+  stream << 88
+    + 96
+  99 + 12 >>
+    stream

trans/haskell.str

@@ -17,33 +17,32 @@ rules
   hs: TopLevel((c,p)) -> $[import System.IO
   data IOStream = StdIO
 
-  stdio :: IO IOStream
-  stdio = return StdIO
-
-  receives :: Show b => IO a -> b -> IO a
-  receives s d = do
-    temp <- s
+  gets :: Show b => a -> b -> IO a
+  gets s d = do
     putStr(show d)
-    return temp
+    return s
 
   main = do
     [p]return [c]]
 
-  hs: Stdio() -> ("stdio", "")
+  hs: Stream() -> ("StdIO", "")
   hs: Int(x) -> (x, "")
-  hs: Sum((c,p)) -> ($[sum [c]], p)
-  hs: Receives((c, p), (d, s)) -> ($[[c] `receives` [d]], <conc-strings>(p,s))
-  hs: Enters((c, p), (d, s)) -> <hsenter>(c,d,<conc-strings>(p,s),<newname>"fos")
+  hs: Sum( (c, p), (d, q)) -> ($[([c] + [d])], <conc-strings>(p,q))
+  hs: Gets((c, p), (d, q)) -> <hsget>(c,d,<conc-strings>(p,q),<newname>"fosgt")
 
-  hsenter: (x, s, p, v) -> (v, <concat-strings>[$[[p]let [v] = [x]], "\n",
-                               $[[s] `receives` [v]], "\n"])
+  hsget: (s, x, p, v) -> (v, <concat-strings>[p, $[[v] <- [s] `gets` [x]],
+                                              "\n"])
 
-  hslist: x -> (<map(Fst); join(|", "); brack>x, <map(Snd); concat-strings>x)
-  brack: x -> $<[<x>]>
+  hs: To(  (c, p), (d, q)) -> <hsto>(c,d,<conc-strings>(p,q),<newname>"fosto")
+
+  hsto: (x, s, p, v) -> (v, <concat-strings>[p, $[let [v] = [x]], "\n",
+                               $[[s] `gets` [v]], "\n"])
+
+  hs: Sequence(l) -> (<last; Fst>l, <map(Snd); concat-strings>l)
 
 strategies
 
-  haskell = bottomup(try(hs <+ hslist))
+  haskell = bottomup(try(hs))
 
   // Interface haskell code generation with editor services and file system
   to-haskell: (selected, _, _, path, project-path) -> (filename, result)

trans/javascript.str

@@ -7,25 +7,24 @@ signature
 
 rules
   js: TopLevel(x) -> $[const Stdio = {
-    receives: v => { process.stdout.write(String(v)); return Stdio; },
+    gets: v => { process.stdout.write(String(v)); return Stdio; },
   }
-  function forwards(data, strm) {
-    strm.receives(data);
+  function to(data, strm) {
+    strm.gets(data);
     return data;
   }
   [x]]
 
-  js: Stdio() -> $[Stdio]
+  js: Stream() -> $[Stdio]
   js: Int(x) -> x
-  js: Sum(x) -> $[[x].reduce((v,w) => v+w)]
-  js: Receives(x, y) -> $[[x].receives([y])]
-  js: Enters(x, y) -> $[forwards([x],[y])]
-
-  jslist: x -> $<[<<join(|", ")>x>]>
+  js: Sum(x,y) -> $[[x] + [y]]
+  js: Gets(x, y) -> $[[x].gets([y])]
+  js: To(x, y) -> $[to([x],[y])]
+  js: Sequence(l) -> <join(|";\n")>l
 
 strategies
 
-  javascript = bottomup(try(js <+ jslist))
+  javascript = bottomup(try(js))
 
   // Interface javascript code generation with editor services and file system
   to-javascript: (selected, _, _, path, project-path) -> (filename, result)

trans/python.str

@@ -9,26 +9,25 @@ rules
 
   py: TopLevel(x) -> $[import sys
   class StdioC:
-    def receives(self, v):
+    def gets(self, v):
       print(v, file=sys.stdout, end='')
       return self
-  def forwards(data,strm):
-    strm.receives(data)
+  def to(data,strm):
+    strm.gets(data)
     return data
   Stdio = StdioC()
   [x]]
 
-  py: Stdio() -> $[Stdio]
-  py: Int(x) -> x
-  py: Sum(x) -> $[sum([x])]
-  py: Receives(x, y) -> $[[x].receives([y])]
-  py: Enters(x, y) -> $[forwards([x],[y])]
-
-  pylist: x -> $<[<<join(|", ")>x>]>
+  py: Stream()    -> $[Stdio]
+  py: Int(x)      -> x
+  py: Sum(x,y)    -> $[[x] + [y]]
+  py: Gets(x, y)  -> $[[x].gets([y])]
+  py: To(x, y)    -> $[to([x],[y])]
+  py: Sequence(l) -> <join(|"\n")>l
 
 strategies
 
-  python = bottomup(try(py <+ pylist))
+  python = bottomup(try(py))
 
   // Interface python code generation with editor services and file system
   to-python: (selected, _, _, path, project-path) -> (filename, result)

trans/util.str

@@ -3,7 +3,7 @@ imports libstrategolib
 
 rules
   join(|infix) : [] -> ""
-  join(|infix) : [x | xs] -> $[[x][<prejoin(|infix)>xs]]
+  join(|infix) : [x | xs] -> <conc-strings>(x, <prejoin(|infix)>xs)
 
   prejoin(|infix) : [] -> ""
-  prejoin(|infix) : [x | xs] -> $[[infix][x][<prejoin(|infix)>xs]]
+  prejoin(|infix) : [x | xs] -> <concat-strings>[infix,x,<prejoin(|infix)>xs]