Expressions calculate a result and substitute the result in place of the expression much like variable references.
 * Are enclosed in ''' '' !-${=-! '' ''' and  ''' '' !-=}-! '' ''' delimiters.
 * May appear anywhere a variable is allowed.
 * May contain the following operators:
   * + - * / ^
   * unary -
   * cos sin tan
   * ( )
   * E notation, e.g., 12E+3

Given:
{{{!define X {1}
!define Y {2}
!define Z {3} }}}

The following expressions yields 10: {{{ !-${= ${X} + ${Y} + ${Z} + 4 =}-! }}}

!3 Actual Markup
!define X {1}
!define Y {2}
!define Z {3}

The result is 10?: ${= ${X} + ${Y} + ${Z} + 4 =} yes!

!3 Advanced Notation

'''Complete Syntax'''
'''!-${=-!''' ['''%''' ''format'' ''':'''] ''expression'' '''!-=}-!'''

Where format is a single numeric or boolean format specifier defined by the Java Formatter class conversions.

'''Examples'''
|''' Mark Up '''                |''' Result '''             |
|!-${=1+2+3=}-!                 |${=1+2+3=}                 |
|!-${=12E+2 + 34=}-!            |${=12E+2 + 34=}            |
|!-${=%03d:1+2+3=}-!            |${=%03d:1+2+3=}            |
|!-${=%02X:10+1=}-!             |${=%02X:8+1=}              |
|!-${= %02x : 10 + 1 =}-!       |${= %02x : 8 + 1 =}        |
|!-${= %03.2f : 10.12345678 =}-!|${= %03.2f : 10.12345678 =}|
|!-${=%b: 1 =}-!                |${=%b:1=}                  |
|!-${=%b: 0 =}-!                |${=%b:0=}                  |
|!-${=%B: 6 =}-!                |${=%B:6=}                  |
|!-${=%B: -2 =}-!               |${=%B:-2=}                 |

!3 Formatting Locale
The formatting locale can be overriden by setting the ''FORMAT_LOCALE'' variable.

'''Example'''
{{{!-!define FORMAT_LOCALE {fr}-!}}}

!see <FitNesse.SuiteAcceptanceTests.SuiteWidgetTests.TestEvaluator