Operators

NAME

operators - List of operators in Sncode.

DESCRIPTION

The following operators are supported in Sncode:

All operators works will all type of variables: - undefined - integer - double - string - null - associative array - array - boolean.

Each operators as is own set of rules for the conversion unless casting is used.

For numerical operators, undefined and null values are considered equal to 0 whereas boolean values are treated as 1 when true and 0 when false.

For string operators, undefined and null values are treated as an empty string whereas boolean values are treated as "true" when true and "false" when false.

Here is the order for operators precedence:

  1. + - .+
  2. * /
  3. % **
  4. | & ^
  5. << >>
  6. = -= = /= %= *= .= &= |= ^= <⇐ >>=
  7. - (unary minus)
  8. ~ (not)
  9. ? :
  10. ()
  11. . []

Numerical operators

Usage:

a = b + c;
a = b / c;// if b and c are integer, the result a will be an integer. If one of operands is double, a will be double.
Operator Description
+ Addition
- Substraction
* Multiplication
/ Division
% Modulo
** Power

Assignment operators

These operators assign a value to their left operand based on the value of their right operand.

Usage:

a = 1;
a += 2; // a now equals 3
Operator Description
= Assignment
+= Addition assignment
-= Subtraction assignment
/= Division assignment
%= Remainder assignment
*= Multiplication assignment
|= Bitwise OR assignment
&= Bitwise AND assignment
.+= String concatenation assignment
>>= Left shift assignment
<<= Right shift assignment

Relational operators for numbers

< <= > >= != <> <⇒

• < : less than
• > : greater than
• <= : less or equal
• >= : greater or uqual
• <=> : compare

• -1 if less than
• 0 if equal
• 1 if greater than

• == : equal
• != : not equal

Relational operators for strings

lt -- less than. Compare the length of 2 strings

le -- less. Compare the length of 2 strings

gt -- greater than. Compare the length of 2 strings

ge -- greater. Compare the length of 2 strings

eq -- equal

ne -- not equal

cmp -- compare two string but return -1, 0, or 1.

st -- check is the first string start with the second string. "/usr/local/website" st "/usr" return true; "/usr/local/website" st ".usr" return false

ns -- check is the first string not start with the second string. "/usr/local/website" ns "/usr" return false; "/usr/local/website" ns ".usr" return true

Regular expressions

Usage:

if "2016-01-01" =~ "^(?P\d\d\d\d)-(?P\d\d)-(?P\d\d)$" then
Operator Description
=~ Does the left expression match the pattern in the right expression (boolean)
!~ Does the left expression NOT match the pattern in the right expression (boolean)

Regular expressions support special flags to alter their behavior:

Usage:

if "2016" =~:iasm "^(?P\d\d\d\d)$" then
Operator Description
x extended (PCRE_EXTENDED)
i case insensitive (PCRE_CASELESS)
m multiline (PCRE_MULTILINE)
s dot match all (PCRE_DOTALL)

For more details, please consult the PCRE Documentation.

String concatenation

Usage:

a = "Hello" .+ " World";
Operator Description
.+ Appends the right expression to the left one

Unary minus

-

Logical operators

Usage:

if !a || (a && b) then // if a is false or both variables are true
Operator Description
! Not (is the expression false)
&& And (are both expressions are true)
|| Or (is either one of the expressions true)

In Sncode, logical operators rely on lazy evaluation, which means that in both of these cases, the function fact won't even be called:

if 0 && fact(1) then // 0 means false so we don't need to go further

and 

if 1 || fact(1) then // 1 means true so we don't need to go further
Lazy evaluation is a strategy which delays the evaluation of an expression until its value is needed (non-strict evaluation) and which also avoids repeated evaluations (sharing). The sharing can reduce the running time of certain functions by an exponential factor over other non-strict evaluation strategies, such as call-by-name.

The benefits of lazy evaluation include:

  • Performance increases by avoiding needless calculations, and error conditions in evaluating compound expressions
  • The ability to construct potentially infinite data structures
  • The ability to define control flow (structures) as abstractions instead of primitives

Binary operators

~(not) |(or) &(and) ^(xor) <<(left shift) >>(right shift)

File operators

Usage:

if -e "/path/to/file.txt" then

If the path starts with a /, it is automatically prefixed with the path to the root directory. Otherwise, it is prefixed with the path of the current script.

Operator Description
-e Check if the file exists (boolean)
-z Check if the file has a size equal to 0 (boolean)
-r Check if the file can be read (boolean)
-w Check if the file can be open for writing (boolean)
-x Check if the file can be executed (boolean)
-l Check if the path points to a link (boolean)
-f Check if the path points to a file (boolean)
-d Check if the path points to a directory (boolean)
-s Return the size of the file (in bytes)
-m Return the modification time of the file (in secs.) since epoch
-a Return the last access time of the file (in secs.) since epoch
-c Return the creation time of file (in secs.) since epoch
-u Return the owner (user) of the file
-g Return the owner group of the file

EXAMPLES

How to group operators

AUTHOR

Written by Pierre Laplante <laplante@sednove.com>, Jean-Georges Guenard, <jg@sednove.com>

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See also

break

Stops execution of a loop

Classes

Object-Oriented Programming in Sncode

for

Used to loop until a condition.

forin

Loop in an arrray.

Functions in Sncode

How to define and call functions in Sncode

Loop Statements

Loops and sequences in SNCODE

Packages

Introduction to packages in Sncode

sncode

Description of the programming environment Extenso by Sednov ...

Variables and data types

Guide to variables and data types in Sncode