Difference between revisions of "Expressions"

Revision as of 12:19, 6 June 2007

FTM expressions are used in the following contexts

• the FTM message box (ftm.mess)
• the FTM definition (ftm.object)
• the expr class/object

The syntax is basically always the same appart from minor context dependent details.

Values and Lists

The values of FTM expressions can be int, float, symbol or references to FTM object. They values can be represended by the following terms:

• a simple value (int, float, symbol)
• a named value
• an element of an object

Examples of simple values are

• 1 ... an int
• -2 ... an int
• 2.3 ... a float
• -4. ... a loat
• 5.67e-4 ... a float
• .89 ... a float
• ten ... a symbol
• 11-12 ... a symbol (because no space!)
• -thirteen ... a symbol

Named values are defined by FTM definitions using ftm.object. The names, always representing a single value, are used in expressions with a leading dollar – '$' – making for example:

• $x
• $myobject

An element

Parenthesis

Parenthesis in FTM expressions – '(' and ')' – always will (try to) evaluate the contained elements to a single value.

Inside parenthesis you'd have either one

• a value (in which case the parenthesis are useless)
• a simple infix expression
• a simple prefix expression