1.Variables and constants

1.1.Identifiers

Identifiers are formed using letters, digits and the special characters _ and ?. Identifiers must start with a letter or _. Identifiers match the [a-zA-Z_]+[a-zA-Z0-9_?]* regular expression.

Examples of identifiers are x, y2, my_var and test?.

Some special predefined constants are:

true

The boolean constant true.

false

The boolean constant false.

mmout

The standard output stream.

mmerr

The standard error stream.

Notice that streams can be used with the operators << as in C++:

mmout << 3 << "\n";

1.2.Literals

mmx-light supports three types of literal constants:

String literals

Strings can be braced into double quotes " … ". Inside such a string a double quote must be blackslashed. In order to avoid blackslashing one can use the stronger string delimiters /" … "/.

s1 := "This is a string"; s2 := "Print \"foo\""; s2 := /"Print "foo"/;

Integer literals

An integer literal is a sequence of digits, possible preceded by a minus sign. It matches the regular expression [-]?[0-9]+. Examples: 123456789123456789, -123.

Floating literals

A floating literal is a sequence of digits with a decimal point inside and an optional exponent. It matches the regular expression [-]?[0-9]+[.][0-9]+[[eE][-]?[0-9]+]?. Some examples:

z := 0.0; w := -3.14159; x := 1.11e2007

Note that 0. is not permited, one must write 0.0.

1.3.Definition and assignation

To assign a value to a variable, we use the operator :=, while constant values are defined by the operator ==, and cannot be modified hereafter.

Mmx]  

a1 := 1

Mmx]  

a1_? == 2; a1_?

Mmx]  

cst: Int == 11111*111111

Mmx]  

mut: Int := 1010*1234

Mmx]  

cst := - cst

Mmx]  

mut := - mut

2.Operators

Here we list the operators in increasing priority order, together with their internal names:

Whenever writing a complex expression you should carefully consider these priority rules in order to avoid using extra parentheses. For example the expression

if ((a*b)+(c)>(d)) then foo ();

should be better written

if a*b + c > d then foo ();

The Mathemagix grammar is specified in the file mmx-parser.ypp of the basix module.

3.Control flow

3.1.Sequence of Instructions

Instructions are separated with ;.

x := 1;
y := 3;
z := x*y;

3.2.Conditionals

The construction is as follows: if condition then block1 else block2.

condition is any expression that evaluates to a boolean. block1 and block2 are either one instruction or a block of instructions braced into {…}. The else part is optional.

if true then 1;
if a = b then 1 else 2;
if i = 0 then { x := 1; y := 2} else { z := 3; mmerr << "error" }

For the sake of readability do not write

if a = 0 then { b := 0 }

but

if a = 0 then b := 0;

instead, since {…} are not needed for a block with one instruction only. Notice that, according to the priority rules of the operators listed above, the expression

if ((a = 0) and (b = 0)) then foo ();

should be written

if a = 0 and b = 0 then foo ();

for the sake of readability.

3.3.Loops

Loops are constructed as follows: [for E1] [while E2] [until E3] [step E4] do block.

Here […] means that the expression is optional. block is an instruction or a sequence of instruction delimited by {…}. break exits the loop, and continue goes to the next step of the loop.

do mmout << "no end "; // This loop has no end
for i in 1..3 do mmout << i << " ";
i := 0; while i < 0 do { mmout << i << " "; i := i + 1 }

4.Comments

Comments starting with // extend to the end of the physical line. Such a comment may appear at the start of a line or following whitespace or code, but not within a string literal. Multi-line comments must be braced into /{ … }/ and can be nested.

x := 1; // Assign 1 to x.

y := 2;
/{ This
   is multi-line
   comment about y.
}/