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=} |

!see <FitNesse.SuiteAcceptanceTests.SuiteWidgetTests.TestEvaluator