Syntax

This page is form only: how to write Wantzel. What it means is language.md, which is binding. For idioms and pitfalls see writing-wantzel.md; for project-level agreements (entry points, name prefixes) see the Conventions section of howto.md.

The forty-one keywords

and       array     begin     bool      break     char      const     continue
div       do        downto    else      end       false     for       forward
function  if        import    include   int       local     mod       not
of        or        procedure real      record    return    schema    shl
shr       str       then      to        tools     true      type      var
while

Case does not distinguish names: Foo, foo and FOO are one name, and so are STORE.SET and store.set — a constant in capitals beside a routine in lower case is a collision, not a convention.

local in front of a top-level var, const, procedure or function keeps that name inside its file; nothing outside can see it. Public is still the default.

A program

import io;                 // a module of the standard library: a name, no quotes
                           // (a file of your own is `include "shapes.wz";`: in quotes)

const
  MAX = 100;
  GREETING = "hello";

type
  Point = record
    x: int;
    y: int;
  end;

var
  count: int;
  grid:  array[0..MAX - 1] of Point;

function twice(n: int): int;
begin
  return n * 2;
end;

procedure greet(who: str);
begin
  io.puts(STDOUT, who);
end;

begin                      // the main block, last
  count := twice(21);
  greet(GREETING);
end.                       // a full stop, not a semicolon

Fixed order: imports and includes, then declarations, then the main block. No header line — a file starts with its first declaration. import names a module of the library inside the compiler; include names a file, relative to the file it stands in — the rules are in language.md. A routine must be declared before use, or forward.

Types

One type per concept: no integer beside int, no single beside real. Text you assemble lives in an array of char; str is what you write between quotes.

var
  n:    int;
  ratio: real;
  ok:   bool;
  c:    char;
  name: str;
  buf:  array[0..255] of char;
  grid: array[0..799] of char;      // 10 rows of 80: row * 80 + col, no nested array

Declaring

const
  MAX = 100;                    // the type follows from the value
  PI  = 3.14159;

type
  Colour = record
    r, g, b: int;               // several names, one type
  end;

var
  i, j, k: int;                 // the same
  p: Colour;

schema and tools

type ConvertArgs = schema
  celsius: real;
end;

tools
  convert(ConvertArgs): ConvertResult "Convert Celsius to Fahrenheit." readonly idempotent;
end;

A schema is a JSON-shaped record type; a tools ... end; block declares an MCP tool table, one line per tool, and the compiler generates its tools/list, argument parsing and dispatch. Form only, here — what each generates is language.md §7 and §7b, which are binding.

Routines

A function returns a value; a procedure does not. Parameters are by value, except an array of T, passed as a reference with its length.

function area(w: int; h: int): int;
begin
  return w * h;
end;

procedure fill(a: array of char; c: char);
var i: int;                     // locals go here, before begin
begin
  i := 0;
  while i < len(a) do begin a[i] := c; i := i + 1; end;
end;

function later(n: int): int; forward;      // declared now, defined below

A function that reaches end without return is a runtime error, not a silent zero.

Statements

x := 1;                                    // assignment
greet("hi");                               // a call

if x > 0 then y := 1;                      // one statement
if x > 0 then y := 1 else y := 2;

if x > 0 then                              // several: begin ... end
begin
  y := 1;
  z := 2;
end;

while x < 10 do x := x + 1;

for i := 1 to 10 do total := total + i;
for i := 10 downto 1 do total := total + i;

while true do
begin
  if done then break;                      // leave the loop
  if skip then continue;                   // next turn
end;

return v;                                  // from a function
return;                                    // from a procedure
halt(1);                                   // end the program with an exit code

Semicolons separate statements; the one before end is optional. end. closes the program.

Operators

/ is real division, div is integer division; mixing them by accident is refused, not rounded. There is no ++, no +=, no ?: and no assignment inside an expression.

Comments

// to the end of the line

That is the only form. { } was removed in 0.2.0: it ended at the first }, so a brace inside the comment text turned the rest of the sentence into code.

Literals

42          -1          1000000                        // integers
3.14        1.0e-9                         // reals
'a'         '\n'        '\x41'             // chars
"text"      "line\n"    "\x00\xff"         // strings
true        false                          // bools

\xHH takes exactly two hex digits, unlike C — so "\x41BC" is three characters, and a generator can write a byte followed by a literal hex character without ambiguity.

Names

A name starts with a letter and may contain letters, digits, underscores and dots — the dot is an ordinary character, used to group names that belong together:

calc.reset;
io.puts(STDOUT, "hi");
store.set(k, v);

That is a naming convention, not a module system: one flat namespace, and calc.reset is simply a name with a dot in it. A part after a dot may start with a digit (Reading.level.1); the first part may not.

What is not here

No pointers, no heap, no new, no garbage collector. No classes, no inheritance, no interfaces. No generics, no overloading, no operator overloading. No exceptions, no threads, no closures, no lambdas. No implicit conversion between types.

Each is a decision, not an omission; design.md argues them. Short version: a construct that costs more than it gives is left out, because the reader of this code is usually a generator in a loop, and every extra way to say something is another way to get it wrong.