initial commit of reduce

2 files changed, 70 insertions, 0 deletions

diff --git a/README.md b/README.md
index 6230bbd..df76593 100644
--- a/README.md
+++ b/README.md
@@ -27,6 +27,7 @@ now in bytecode
  - [ ] bounds issues (`first`/`last` on empty sequences) crashes entirely
  - [ ] constants get duplicated in chunks
  - [ ] a space at the end of (definitions? lists?) crashes
+ - [ ] HOF can't take in builtins (they're not actually in the global environment)
  - [ ] i mean, nearly nothing works
 
 ## things that hopefully work
diff --git a/compiler.d b/compiler.d
index 8cb65ee..9ae009d 100644
--- a/compiler.d
+++ b/compiler.d
@@ -401,6 +401,72 @@ class Compiler {
         this.func.chunk.writeOp(OpCode.OP_LIST_N, args[0].line);
     }
 
+    void compileReduce(Form[] args) {
+        // TODO how do we identify/propagate errors?
+        if (args.length != 3) {
+            this.error(format("'reduce': expected [3] arguments, received %d", args.length), -1);
+            return;
+        }
+        ValueType vt = this.resolve(args[0], ValueType.ANY);  // resolves the function
+        vt = this.resolve(args[1], ValueType.ANY);            // resolves the list
+
+        vt = this.resolve(args[2], ValueType.ANY);            // resolves the accumulator
+
+        this.func.chunk.writeOp(OpCode.OP_ROTATE_N, args[0].line);
+        this.func.chunk.writeOp(to!ubyte(3), args[0].line);     // | [ acc ] [ fn ] [ list ]
+
+        // we're going to jump back to this point, so let's keep track of our location
+        int jumpBack = to!int(this.func.chunk.code.length);
+
+        // with our list on top of the stack, let's check for nil to see if we're done
+        this.func.chunk.writeOp(OpCode.OP_DUPLICATE, args[0].line);  // | [ acc ] [ fn ] [ list ] [ list ]
+        this.func.chunk.writeOp(OpCode.OP_IS_NIL, args[0].line);     // | [ acc ] [ fn ] [ list ] [ bool ]
+
+        // we'll jump from here to the end if we have nil
+        int nilJump = this.jump(OpCode.OP_JUMP_IF_TRUE);  // TODO if we're using "falsey", we could cut an instruction here
+
+        // get rid of the boolean on top
+        this.func.chunk.writeOp(OpCode.OP_POP, args[0].line);     // | [ acc ] [ fn ] [ list ]
+
+        // duplicate the function and list, and rotate it below the length (we'll need it later)
+        this.func.chunk.writeOp(OpCode.OP_DUPLICATE_2, args[0].line);    // | [ acc ] [ fn ] [ list ] [ fn ] [ list ]
+        this.func.chunk.writeOp(OpCode.OP_ROTATE_N, args[0].line);
+        this.func.chunk.writeOp(to!ubyte(5), args[0].line);           // | [ list ] [ acc ] [ fn ] [ list ] [ fn ]
+        this.func.chunk.writeOp(OpCode.OP_ROTATE_N, args[0].line);
+        this.func.chunk.writeOp(to!ubyte(5), args[0].line);           // | [ fn ] [ list ] [ acc ] [ fn ] [ list ]
+
+        // get the first item from the top list, then run the function on it (we know there's always 1 argument)
+        this.func.chunk.writeOp(OpCode.OP_FIRST, args[0].line);       // | [ fn ] [ list ] [ acc ] [ fn ] [ item ]
+
+        // rotate the accumulator and item to the top
+        this.func.chunk.writeOp(OpCode.OP_ROTATE_N, args[0].line);
+        this.func.chunk.writeOp(to!ubyte(3), args[0].line);           // | [ fn ] [ list ] [ item ] [ acc ] [ fn ]
+        this.func.chunk.writeOp(OpCode.OP_ROTATE_N, args[0].line);
+        this.func.chunk.writeOp(to!ubyte(3), args[0].line);           // | [ fn ] [ list ] [ fn ] [ item ] [ acc ]
+
+        // call the function
+        this.func.chunk.writeOp(OpCode.OP_CALL, args[0].line);
+        this.func.chunk.writeOp(to!ubyte(2), args[0].line);           // | [ fn ] [ list ] [ fn(item, acc) ]
+
+        // rotate the accumulator behind the fn/list
+        this.func.chunk.writeOp(OpCode.OP_ROTATE_N, args[0].line);
+        this.func.chunk.writeOp(to!ubyte(3), args[0].line);           // | [ fn(item, acc) ] [ fn ] [ list ]
+
+        // get the rest of the list
+        this.func.chunk.writeOp(OpCode.OP_REST, args[0].line);        // | [ fn(item, acc) ] [ fn ] [ rest(list) ]
+
+        // jump back to the top of the loop
+        this.jumpBackTo(OpCode.OP_JUMP_TO, jumpBack);
+
+        // jump here when we have a nil
+        this.patchJump(nilJump);              // | [ fn(first) ] ... [ fn(last) ] [ length ] [ fn ] [ nil ] [ true ]
+
+        // pop the unneeded state at the top, leaving the result at the top
+        this.func.chunk.writeOp(OpCode.OP_POP, args[0].line);
+        this.func.chunk.writeOp(OpCode.OP_POP, args[0].line);
+        this.func.chunk.writeOp(OpCode.OP_POP, args[0].line);  // | [ acc ]
+    }
+
     // LISP-Y
     void compileBlock(Form form) {
         Block block = cast(Block)form;
@@ -854,6 +920,9 @@ class Compiler {
             case "map":
                 this.compileMap(cons.tail);
                 break;
+            case "reduce":
+                this.compileReduce(cons.tail);
+                break;
 
             // STRINGS
             case "concat":