Forest(PPL)

Variables, constants, arrays

Every value is stored as a Unicode string: 5.2 is kept as "5.2", booleans as "True" and "False". A leading underscore makes a name private. The names result and all are reserved.

var x = 0;
x = 1 + 2;              // "set" may be omitted
const PI2 = 6.28;
array y[3];
y[x - 1] = 2 + 3;
array colors[] = {"Red", "Green"};
writearray colors row;

var (x [0]);
set (x) (+(1)(2));
array (y[3]);
set (y[+(1)(2)]) (0);
set (x) ( -(0)(+(3)(2)) );  // x = -(3+2)

Declaring a name twice fails with name [x] already exists. Delete it with del x, or allow redeclaration with recreate yes.

Conditions and loops

for(i, start, end[, step]) becomes a ppl loop … do block. Braces around an if or for body may be dropped when it holds one simple statement. With nested ifs, keep the braces on the outer one.

for(i, 0, 3)
{
  if (i == 0)
  {
     write#("i == 0");
     continue;
  }
  else
    write#("i != 0 = {0}", i);
}
x = 1 == 1 ? t : f;

loop (i)(0)(3)(1)
(
   do
   (
     (write(hello))
     (write(world))
   )
);

Also available: switch / case / default, break, continue and setloopend.

Functions

A program runs top to bottom; there is no main. Results come back through parameters. Local variables live in the Local tree and are removed when the function returns.

function f(a, b, c, q)
{
  q = a + b + c;
}
var res;
call f(1, 2, 3, res);
write#("res={0}", res);   // res=6

sumdata string;
call f(1, 2, 3, res);
write#("res={0}", res);   // res=123

createnode Functions.Calc;
function
(
  Functions.Calc.Sum(result1)(n1)(n2)
  (
     (set(result1)(+(n1) (n2)))
  )
);

Parameters can be typed (array: arr, storage: stor). Functions support finally and failure blocks, plus delegates and callbacks: delegate, dlgtcall, callback.

Nodes, public and private

A node groups data and functions under one name. Anything starting with _ is visible only to functions of its own node.

createnode N1;
var N1.x  = "public var N1.x";
var N1._x = "private var N1._x";

function N1._f()    // private
{
    write(N1.x);
    write(N1._x);
}
function N1.f()     // public
{
   N1._f();
}
N1.f();
write(N1._x);   // Error: [GetValue] [N1._x] private object, no access

Give a long name a short alias with using x = xxxxx.

Storage: multidimensional and jagged arrays

Storage holds data of any dimension, including rows of different lengths. Work with it through sget, sset, swrite, sinfo, sresize and the StorageLib library, which adds sorting, median, Unique, Shuffle and PushRow.

storage s[2,2];
s[0,0] = "left top";
s[0,1] = s[0,0];

storage (stor)(2)(2)
sset (stor)(0)(0)("var (x)(0);d")
eval (sget(stor)(0)(0))

Save data to disk and restore it with savedata and readdata.

StorageLib: indices pick the level

Every StorageLib function counts its own parameters from the right; the parentheses before them are indices. The same call therefore works on the whole array, a slice or a row. For a 2×3×2 array holding 1..12:

storage s;
storage.ReadFile(s)("test_nd.csv")(",");
storage.Sum(s)(res);           // 78  whole array
storage.Sum(s)(1)(res);        // 57  slice s[1]
storage.Sum("s[1][2]")(res);   // 23  row s[1][2] = 11 + 12
storage.PushRow(s)(0);         // adds a zero-filled row to slice 0

Statistics add up every number below the chosen node and skip text; Push, Pop, Sort and similar functions need the indices to reach a row. See the reference for the rules.

Libraries

The Main library is always loaded. Others come in with import or through UserImportN lines in Configuration.data. Build your own extension as a DLL with CodeGen.exe.

import Console;
import String;

var text = "##Hello World!##";
array colors[] = {"Black","DarkBlue","DarkGreen","DarkCyan",
                  "DarkRed","DarkMagenta","DarkYellow","Gray",
                  "DarkGray","Blue","Green","Cyan",
                  "Red","Magenta","Yellow","White"};
array ArrayChars;
call String.ToCharArray(text, ArrayChars);
for(i, 0, length(text))
{
    Console.ForegroundColor(colors[i]);
    Console.Write(ArrayChars[i]);
}
Console.DefaultColors();

Help for a library: Math.help. Help for one function: Math.help(Sinh). Loaded libraries: importlist.

eval, debugging, timing

A script can build ppl code as a string and run it immediately. That lets you change variables and logic at runtime without restarting the engine.

>var x = "var(r); set(r)(/(180)(Math.PI())); write(r);";
>eval(x);
57.29577951308232
>write(eval("+(1)(2)"))
3

start;
array x[10];
for(i, 0, length(x))
{
   x[i] = i;
}
writearray x row;
stop("test duration:");   // test duration: 0.7918 msec

To see what your program does: dstree prints the syntax tree of every statement, printscope shows the scope stack, traceppl yes traces execution, and suspend pauses a script so you can type commands by hand.