integer - Evaluate a pure integer expression


integer arg ?arg arg ...?


Evaluates the arguments as an arithmetic expression and returns the value.

The result of an integer command should be treated only as a string in Tcl commands. One needs to be wary of commands which assume the use of expr such as the if, for and while tests. Neither can the result of a integer command be used safely in expr. The command is not intended for number crunching applications but rather as a vehicle for applications in number theory, function theory and artificial intelligence.

Typically integer expressions will be constructed by a Tcl script and executed using a command like:
set x [eval integer $intexpr].


An argument may be an operand, an operator or a parenthesis.

An operand is of canonical Tcl decimal integer form; that is described by the regular expressions 0 or [1-9][0-9]* or -[1-9][0-9]*. The maximum length of a long integer is determined by system resources such as memory.

An operator may be one of + - * / or % . The three types of operator, additive ( + - ) , multiplicative ( * / ), and modulus (%), must be grouped seperately by parentheses. The five operators return signed integers according to the same rules for expr. Within the additive group the + operators must preceed the - operators and similarly in the multiplicative group the * operators must preceed the / operators. The modulus operator % may not be grouped associatively. The expression is evaluated from left to right. The group ( $a1 + $a2 - $a3 - $a4 - ... - $an ) is evaluated as ($a1 + $a2 - ( $a3 + $a4 + ... + $an ) ) and similarly for the multiplicative group. For the multiplicative group this ensures that multiplications are done before any divisions so that whole divisions are performed where ever possible. This is a much more restricted form of arithmetic expression syntax than in C expressions for instance, as it is designed for people who do not know about syntactic grammar conventions.