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A program is a set of declarations followed by a compound
statement. Here is the minimal T3X program:
A comment is started with an exclamation point (!) and extends
up to the end of the current line. Example:
DO END ! Do nothing
-----[ CONST name = cvalue, ... ; ]-----------------------------
Assign names to constant values.
Example: CONST false = 0, true = %1;
VAR name, ... ;
-----[ VAR name[cvalue], ... ; ]--------------------------------
VAR name::cvalue, ... ;
Define variables, vectors, and byte vectors, respectively.
Different definitions may be mixed. Vector elements start at
an index of 0.
Example: VAR stack[STACK_LEN], ptr;
-----[ STRUCT name = name_1, ..., name_N; ]---------------------
Shorthand for CONST name_1 = 0, ..., name_N = N-1, name = N;
Used to impose structure on vectors and byte vectors.
-----[ DECL name(cvalue), ... ; ]-------------------------------
Declare functions whose definitions follow later, where the
cvalue is the number of arguments. Used to implement mutual
Example: DECL odd(1);
even(x) RETURN x=0-> 1: odd(x-1);
odd(x) RETURN x=1-> 1: even(x-1);
-----[ name(name_1, ...) statement ]----------------------------
Define function "name" with arguments "name_1", ... and a
statement as its body. The number of arguments must match
any previous DECL of the same function.
The arguments of a function are only visible within the
(statement) of the function.
Example: hello(s, x) DO VAR i;
FOR (i=0, x) DO
(Writes() writes a string; it is defined later in this text.)
-----[ name := expression; ]------------------------------------
Assign the value of an expression to a variable.
Example: DO VAR x; x := 123; END
-----[ name[value]... := value; ]-------------------------------
name::value := value;
Assign the value of an expression to an element of a vector
or a byte vector. Multiple subscripts may be applied to to a
vec[i][j]... := i*j;
In general, VEC[i][j] denotes the j'th element of the i'th
element of VEC.
Note that the :: operator is right-associative, so v::x::i
equals v::(x::i). This is particularly important when mixing
subscripts, because
vec[i]::j[k] := 0;
would assign 0 to the j[k]'th element of vec[i]. (This makes
sense, because vec[i]::j would not deliver a valid address.)
-----[ name(); ]-------------------------------
name(expression_1, ...);
Call the function with the given name, passing the values of the
expressions to the function. An empty set of parentheses is used
to pass zero arguments. The result of the function is discarded.
For further details see the description of function calls in the
expression section.
-----[ IF (condition) statement_1 ]-------------------
IE (condition) statement_1 ELSE statement_2
Both of these statements run statement_1, if the given
condition is true.
In addition, IE/ELSE runs statement_2, if the conditions is
false. In this case, IF just passes control to the subsequent
Example: IE (0)
IF (1) RETURN 1;
The example always returns 2, because only an IE statement can
have an ELSE branch. There is no "dangling else" problem.
-----[ WHILE (condition) statement ]----------------------------
Repeat the statement while the condition is true. When the
condition is not true initially, never run the statement.
Example: ! Count from 1 to 10
i := 0;
WHILE (i < 10)
i := i+1;
---[ FOR (name=expression_1, expression_2, cvalue) statement ]--
FOR (name=expression_1, expression_2) statement
Assign the value of expression_1 to name, then compare name to
expression_2. If cvalue is not negative, repeat the statement
while name < expression_2. Otherwise repeat the statement while
name > expression_2. After running the statement, add cvalue
to name. Formally:
name := expression_1;
WHILE ( cvalue > 0 /\ name < expression \/
cvalue < 0 /\ name > expression )
name := name + cvalue;
When the cvalue is omitted, it defaults to 1.
Examples: DO VAR i;
FOR (i=1, 11); ! count from 1 to 10
FOR (i=10, 0, %1); ! count from 10 to 1
-----[ LEAVE; ]-------------------------------------------------
Leave the innermost WHILE or FOR loop, passing control to the
first statement following the loop.
Example: DO VAR i; ! Count from 1 to 50
FOR (i=1, 100) IF (i=50) LEAVE;
-----[ LOOP; ]--------------------------------------------------
Re-enter the innermost WHILE or FOR loop. WHILE loops are
re-entered at the point where the condition is tested, and
FOR loops are re-entered at the point where the counter is
Example: DO VAR i; ! This program never prints X
FOR (i=1, 10) DO
T.WRITE(1, "x", 1);
-----[ RETURN expression; ]-------------------------------------
Return a value from a function. For further details see the
description of function calls in the expression section.
Example: inc(x) RETURN x+1;
-----[ HALT cvalue; ]-------------------------------------------
Halt program and return the given exit code to the operating
Example: HALT 1;
-----[ DO statement ... END ]-------------------
DO declaration ... statement ... END
Compound statement of the form DO ... END are used to place
multiple statements in a context where only a single statement
is expected, like selection, loop, and function bodies.
A compound statement may declare its own local variables,
constant, and structures (using VAR, CONST, or STRUCT). A
local variable of a compound statement is created and
allocated at the beginning of the statement is ceases to
exist at the end of the statement.
Note that the form
DO declaration ... END
also exists, but is essentially an empty statement.
Example: DO var i, x; ! Compute 10 factorial
x := 1;
for (i=1, 10)
x := x*i;
-----[ DO END ]-------------------------------------------------
These are both empty statements or null statements. They do not
do anything when run and may be used as placeholders where a
statement would be expected. They are also used to show that
nothing is to be done in a specific situation, like in
IE (x = 0)
ELSE IE (x < 0)
Examples: FOR (i=0, 100000) DO END ! waste some time
An expression is a variable or a literal or a function call or
a set of operators applied to one of these. There are unary,
binary, and ternary operators.
Examples: -a ! negate a
b*c ! product of b and c
x->y:z ! if x then y else z
In the following, the symbols X, Y, and Z denote variables or
These operators exist (P denotes precedence, A associativity):
| X[Y] | 9 | L | the Y'th element of the vector X |
| X::Y | 9 | R | the Y'th byte of the byte vector X |
| -X | 8 | - | the negative value of X |
| ~X | 8 | - | the bitwise inverse of X |
| \X | 8 | - | logical NOT of X |
| @X | 8 | - | the address of X |
| X*Y | 7 | L | the product of X and Y |
| Y/Y | 7 | L | the integer quotient of X and Y |
| X mod Y | 7 | L | the division remainder of X and Y |
| X+Y | 6 | L | the sum of X and Y |
| X-Y | 6 | L | the difference between X and Y |
| X&Y | 5 | L | the bitwise AND of X and Y |
| X|Y | 5 | L | the bitwise OR of X and Y |
| X^Y | 5 | L | the bitwise XOR of X and Y |
| X<<Y | 5 | L | X shifted to the left by Y bits |
| X>>Y | 5 | L | X shifted to the right by Y bits |
| X<Y | 4 | L | %1, if X is less than Y, else 0 |
| X>Y | 4 | L | %1, if X is less than Y, else 0 |
| X<=Y | 4 | L | %1, if X is less/equal Y, else 0 |
| X>=Y | 4 | L | %1, if X is greater/equal Y, else 0|
| X=Y | 3 | L | %1, if X equals Y, else 0 |
| X\=Y | 3 | L | %1, if X does not equal Y, else 0 |
| X/\Y | 2 | L | if X then Y else 0 |
| | | | (short-circuit logical AND) |
| X\/Y | 1 | L | if X then X else Y |
| | | | (short-circuit logical OR) |
| X->Y:Z | 0 | - | if X then Y else Z |
Higher precedence means that an operator binds stronger, e.g.
-X::Y actually means -(X::Y).
Left-associativity (L) means that x+y+z = (x+y)+z and
right-associativity (R) means that x::y::z = x::(y::z).
A condition is an expression appearing in a condition context,
like the condition of an IF or WHILE statement or the first
operand of the X->Y:Z operator.
In an expression context, the value 0 is considered to be
"false", and any other value is considered to be true. For
X=X is true
1=2 is false
"x" is true
5>7 is false
The canonical truth value, as returned by 1=1, is %1.
When a function call appears in an expression, the result of
the function, as returned by RETURN is used as an operand.
A function call is performed as follows:
Each actual argument in the call
function(argument_1, ...)
is passed to the function and bound to the corresponding formal
argument ("argument") of the receiving function. The function
then runs its statement, which may produce a value via RETURN.
When no RETURN statement exists in the statement, 0 is returned.
Function arguments evaluate from the left to the right, so in
A is guaranteed to evaluate before B and C and B is guaranteed
to evaluate before C.
Example: pow(x, y) DO VAR a;
a := 1;
a := a*x;
y := y-1;
x := pow(2,10);
An integer is a number representing its own value. Note that
negative numbers have a leading '%' sign rather than a '-' sign.
While the latter also works, it is, strictly speaking, the
application of the '-' operator to a positive number, so it may
not appear in cvalue contexts.
Integers may have a '0x' prefix (after the '%' prefix, if
that also exists). In this case, the subsequent digits will
be interpreted as a hexa-decimal number.
Examples: 0
Characters are integers internally. They are represented by
single characters enclosed in single quotes. In addition, the
same escape sequences as in strings may be used.
Examples: 'x'
A string is a byte vector filled with characters. Strings are
delimited by '"' characters and NUL-terminated internally. All
characters between the delimiting double quotes represent
themselves. In addition, the following escape sequences may be
used to include some special characters:
\a BEL Bell
\b BS Backspace
\e ESC Escape
\f FF Form Feed
\n LF Line Feed (newline)
\q " Quote
\r CR Carriage Return
\s Space
\t HT Horizontal Tabulator
\v VT Vertical Tabulator
\\ \ Backslash
Examples: ""
"hello, world!\n"
"\qhi!\q, she said"
A packed table is a byte vector literal. It is a set of cvalues
delimited by square brackets and separated by commas. Note that
string notation is a short and portable, but also limited,
notation for byte vectors. For instance, the byte vectors
PACKED [ 'H', 'E', 'L', 'L', 'O', 0 ]
are identical. Byte vectors can contain any values in the range
from 0 to 255.
Examples: PACKED [ 1 ]
PACKED [ 1, 2, 3 ]
PACKED [ 14, 'H', 'i', 15 ]
A table is a vector literal, i.e. a sequence of values. It is
delimited by square brackets and elements are separated by
commas. Table elements can be cvalues, strings, and tables.
Examples: [1, 2, 3]
["5 times -7", %35]
The dynamic table is a special case of the table in which one
or multiple elements are computed at program run time. Dynamic
table elements are enclosed in parentheses. E.g. in the table
["x times 7", (x*7)]
the value of the second element would be computed and filled
in when the table is being evaluated. Note that dynamic table
elements are being replaced in situ, and remain the same only
until they are replaced again.
Multiple dynamic elements may be enclosed by a single pair of
parentheses. For instance, the following tables are the same:
[(x), (y), (z)]
[(x, y, z)]
A cvalue (constant value) is an expression whose value is known
at compile time. In full T3X, this is a large subset of full
expressions, but in T3X9, it it limited to the following:
* integers
* characters
* constants
as well as (given that X and Y are one of the above):
* X+Y
* X*Y
Symbolic names for variables, constants, structures, and
functions are constructed from the following alphabet:
* the characters a-z
* the digits 0-9
* the special characters '_' and '.'
The first character of a name must be non-numeric, the remaining
characters may be any of the above.
Upper and lower case is not distinguished, the symbolic names
FOO, Foo, foo
are all considered to be equal.
By convention,
* CONST names are all upper-case
* STRUCT names are all upper-case
* global VAR names are capitalized
* local VAR names are all lower-case
* function names are all lower-case
Keywords, like VAR, IF, DO, etc, are sometimes printed in upper
case in documentation, but are usually in lower case in actual
There is a single name space without any shadowing in T3X:
* all global names must be different
* no local name may have the same name as a global name
* all local names in the same scope must be different
The latter means that local names may be re-used in subsequent
scopes, e.g.:
f(x) RETURN x;
g(x) RETURN x;
would be a valid program. However,
f(x) DO VAR x; END !!! WRONG !!!
would not be a valid program, because VAR x; redefines the
argument of F.
The following built-in functions exist in T3X9. They resemble
the functions of the T3X core module of the full language, i.e.
a T3X9 program can be compiled by a T3X compiler by adding the
following code to the top of the program:
MODULE name(t3x);
OBJECT t[t3x];
These functions are built into the T3X9 compiler, though, and
do not have to be declared in any way. The '.' in the function
names resembles the message operator of the full language.
T3X9r3 accepts (and ignores) the above declarations at the
beginning of a program. A program containing these declarations
can be compiled by any T3X compiler.
-----[ T.MEMCOMP(b1, b2, len) ]---------------------------------
Compare the first LEN bytes of the byte vectors B1 and B2.
Return the difference of the first pair of mismatching bytes.
A return code of 0 means that the compared regions are equal.
Example: t.memcomp("aaa", "aba", 3) ! gives 'b'-'a' = %1
-----[ T.MEMCOPY(bs, bd, len) ]---------------------------------
Copy LEN bytes from the byte vector BS (source) to the byte
vector BD (destination). Return 0.
Unlike in the full T3X language, BS and BD may not overlap.
Example: DO VAR b::100; t.memcopy(b, "hello", 5); END
-----[ T.MEMFILL(bv, b, len) ]----------------------------------
Fill the first LEN bytes of the byte vector BV with the byte
value B. Return 0.
Example: DO VAR b::100; t.memfill(b, 0, 100); END
-----[ T.MEMSCAN(bv, b, len) ]----------------------------------
Locate the first occurrence of the byte value B in the first LEN
bytes of the byte vector BV and return its offset in the vector.
When B does not exist in the given region, return %1.
Example: t.memscan("aaab", 'b', 4) ! returns 3
-----[ T.CREATE(path) ]-----------------------------------------
Create a file with the given PATH, open it, and return its file
descriptor. In case of an error, return -1.
Example: t.create("new-file");
-----[ T.OPEN(path, mode) ]-------------------------------------
Open file PATH in the given MODE, where 0=read-only, 1=write-
only, and 2=read/write. Return -1 in case of an error.
Example: t.open("existing-file", 0);
-----[ T.CLOSE(fd) ]--------------------------------------------
Close the file descriptor FD. Return 0 for success and -1 in
case of an error.
Example: DO var fd;
fd := t.create("file");
if (fd >= 0) t.close();
-----[ T.READ(fd, buf, len) ]-----------------------------------
Read up to LEN characters from the file descriptor FD into the
buffer BUF. Return the number of characters actually read.
Return %1 in case of an error.
Example: DO b::100; t.read(0, b, 99); END
-----[ T.WRITE(fd, buf, len) ]----------------------------------
Write LEN characters from the buffer BUF to the file descriptor
FD. Return the number of characters actually written. Return %1
in case of an error.
Example: t.write(1, "hello, world!\n", 14);
-----[ T.RENAME(path, new) ]------------------------------------
Rename the file given in PATH to NEW. Return 0 for success and
-1 in case of an error.
Example: t.rename("old-name", "new-name");
-----[ T.REMOVE(path) ]-----------------------------------------
Remove the file given in PATH. Return 0 for success and -1 in
case of an error.
Example: t.remove("temp-file");
T3X implements variadic functions (i.e. functions of a variable
number of arguments) using dynamic tables. For instance, the
following function returns the sum of a vector of arguments:
sum(k, v) DO var i, n;
n := 0;
FOR (i=0, k)
n := n+v[i];
Its is an ordinary function returning the sum of a vector. It
can be considered to be a variadic function, because a dynamic
table can be passed to it in the V argument:
sum(5, [(a,b,c,d,e)])
var ntoa_buf::100;
ntoa(x) do var i, k;
if (x = 0) return "0";
i := 0;
k := x<0-> -x: x;
while (k > 0) do
i := i+1;
k := k/10;
i := i+1;
if (x < 0) i := i+1;
ntoa_buf::i := 0;
k := x<0-> -x: x;
while (k > 0) do
i := i-1;
ntoa_buf::i := '0' + k mod 10;
k := k/10;
if (x < 0) do
i := i-1;
ntoa_buf::i := '-';
return @ntoa_buf::i;
str.length(s) return t.memscan(s, 0, 32767);
writes(s) t.write(1, s, str.length(s));
fib(n) do var r1, r2, i, t;
r1 := 0;
r2 := 1;
for (i=1, n) do
t := r2;
r2 := r2 + r1;
r1 := t;
return r2;
do var i;
for (i=1, 11) do