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) such as '1', '2.3' and 'three'
- a named value such as $myobj
- an element of an object such as '$myobj[7]'
- a numberd argument such as '$1'
Examples of simple values are:
- 1 ... an int
- -2 ... an int
- 2.3 ... a float
- -4. ... a loat
- 5.67e-4 ... a float
- .89 ... a float
- ten ... a symbol
- 11-12 ... a symbol (because no space!)
- -thirteen ... a symbol
Named values are defined by FTM definitions using ftm.object. The names, always representing a single value, are used in expressions with a leading dollar – '$' – making for example:
- $x
- $myobject
An element of an object can be accessed with FTM expressions using brackets – '[' and ']', for example:
- $myvec[0]
- $mymat[0 0]
- $mydict[x]
Anything more complex than $-names and []-elements happens within parenthesis.
Single values can be concatenated to argument lists (in the message box lists or messages) with spaces like:
- 1 2.3 three
- 4 + 5.5 / six
- $myobj set 7 9.8 ten
Argument lists within parenthesis will be evaluated as expressions.
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