Expressions

PDS supports the usual arithmetic operators (+, -, *, /) with standard precedence. All arithmetic operations use double-precision floating-point values.

PDS also supports the standard C-style comparison operators (==, !=, >, <, >=, <=). These operators perform numeric comparison if both arguments are valid numbers; otherwise, they perform string comparison. They evaluate to zero if the comparison is false and to a non-zero value if it is true.

PDS does not support the relational operators and, or, and not.

Backquote expressions

A string enclosed in backquotes (‘such as this‘) has variable substitution performed on it, and the result is evaluated in a subshell. The standard output of the command is collected, newlines and linefeed characters are replaced by spaces, and trailing whitespace is removed. The result is the value of the expression.