An expression is a string which defines a formula or criteria, that's evaluated at runtime. The expression may be a combination of variables, constants, strings, dates and operators/functions. For instance 1000 format `` gets 1,000.00 for US format, while 1.000,00 is displayed for German format.
The Exontrol's eXPression component is a syntax-editor that helps you to define, view, edit and evaluate expressions. Using the eXPression component you can easily view or check if the expression you have used is syntactically correct, and you can evaluate what is the result you get giving different values to be tested. The Exontrol's eXPression component can be used as an user-editor, to configure your applications.
Usage examples:
Listed bellow are all predefined constants, operators and functions the general-expression supports:
The constants can be represented as:
The predefined constants are:
The supported binary arithmetic operators are:
The supported unary boolean operators are:
The supported binary boolean operators are:
The supported binary boolean operators, all these with the same priority 0, are :
The supported binary range operators, all these with the same priority 5, are :
The supported binary operators, all these with the same priority 0, are :
:= (Store operator), stores the result of expression to variable. The syntax for := operator is
variable := expression
where variable is a integer between 0 and 9. You can use the =: operator to restore any stored variable ( please make the difference between := and =: ). For instance, (0:=dbl(value)) = 0 ? "zero" : =:0, stores the value converted to double, and prints zero if it is 0, else the converted number. Please pay attention that the := and =: are two distinct operators, the first for storing the result into a variable, while the second for restoring the variable
=: (Restore operator), restores the giving variable ( previously saved using the store operator ). The syntax for =: operator is
=: variable
where variable is a integer between 0 and 9. You can use the := operator to store the value of any expression ( please make the difference between := and =: ). For instance, (0:=dbl(value)) = 0 ? "zero" : =:0, stores the value converted to double, and prints zero if it is 0, else the converted number. Please pay attention that the := and =: are two distinct operators, the first for storing the result into a variable, while the second for restoring the variable
The supported ternary operators, all these with the same priority 0, are :
expression ? true_part : false_part
, while it executes and returns the true_part if the expression is true, else it executes and returns the false_part. For instance, the %0 = 1 ? 'One' : (%0 = 2 ? 'Two' : 'not found') returns 'One' if the value is 1, 'Two' if the value is 2, and 'not found' for any other value. A n-ary equivalent operation is the case() statement, which is available in newer versions of the component.
The supported n-ary operators are (with priority 5):
expression array (c1,c2,c3,...cn)
, where the c1, c2, ... are constant elements. The constant elements could be numeric, date or string expressions. For instance the month(value)-1 array ('J','F','M','A','M','Jun','J','A','S','O','N','D') is equivalent with month(value)-1 case (default:''; 0:'J';1:'F';2:'M';3:'A';4:'M';5:'Jun';6:'J';7:'A';8:'S';9:'O';10:'N';11:'D').
expression in (c1,c2,c3,...cn)
, where the c1, c2, ... are constant elements. The constant elements could be numeric, date or string expressions. For instance the value in (11,22,33,44,13) is equivalent with (expression = 11) or (expression = 22) or (expression = 33) or (expression = 44) or (expression = 13). The in operator is not a time consuming as the equivalent or version is, so when you have large number of constant elements it is recommended using the in operator. Shortly, if the collection of elements has 1000 elements the in operator could take up to 8 operations in order to find if an element fits the set, else if the or statement is used, it could take up to 1000 operations to check, so by far, the in operator could save time on finding elements within a collection.
expression switch (default,c1,c2,c3,...,cn)
, where the c1, c2, ... are constant elements, and the default is a constant element being returned when the element is not found in the collection. The constant elements could be numeric, date or string expressions. The equivalent syntax is "%0 = c 1 ? c 1 : ( %0 = c 2 ? c 2 : ( ... ? . : default) )". The switch operator is very similar with the in operator excepts that the first element in the switch is always returned by the statement if the element is not found, while the returned value is the value itself instead -1. For instance, the %0 switch ('not found',1,4,7,9,11) gets 1, 4, 7, 9 or 11, or 'not found' for any other value. As the in operator the switch operator uses binary searches for fitting the element, so it is quicker that iif (immediate if operator) alterative.
expression case ([default : default_expression ; ] c1 : expression1 ; c2 : expression2 ; c3 : expression3 ;....)
If the default part is missing, the case() operator returns the value of the expression if it is not found in the collection of cases ( c1, c2, ...). For instance, if the value of expression is not any of c1, c2, .... the default_expression is executed and returned. If the value of the expression is c1, then the case() operator executes and returns the expression1. The default, c1, c2, c3, ... must be constant elements as numbers, dates or strings. For instance, the date(shortdate(value)) case (default:0 ; #1/1/2002#:1 ; #2/1/2002#:1; #4/1/2002#:1; #5/1/2002#:1) indicates that only #1/1/2002#, #2/1/2002#, #4/1/2002# and #5/1/2002# dates returns 1, since the others returns 0. For instance the following sample specifies the hour being non-working for specified dates: date(shortdate(value)) case(default:0;#4/1/2009# : hour(value) >= 6 and hour(value) <= 12 ; #4/5/2009# : hour(value) >= 7 and hour(value) <= 10 or hour(value) in(15,16,18,22); #5/1/2009# : hour(value) <= 8) statement indicates the working hours for dates as follows:
- #4/1/2009#, from hours 06:00 AM to 12:00 PM
- #4/5/2009#, from hours 07:00 AM to 10:00 AM and hours 03:00PM, 04:00PM, 06:00PM and 10:00PM
- #5/1/2009#, from hours 12:00 AM to 08:00 AM
The in, switch and case() use binary search to look for elements so they are faster then using iif and or expressions. Obviously, the priority of the operations inside the expression is determined by ( ) parenthesis and the priority for each operator.
The supported conversion unary operators are:
The bitwise operators for numbers are:
The operators for numbers are:
The ' flags' for format operator is a list of values separated by | character such as 'NumDigits|DecimalSep|Grouping|ThousandSep|NegativeOrder|LeadingZero' with the following meanings:
The operators for strings are:
The operators for dates are:
The expression supports also immediate if ( similar with iif in visual basic, or ? : in C++ ) ie cond ? value_true : value_false, which means that once that cond is true the value_true is used, else the value_false is used. Also, it supports variables, up to 10 from 0 to 9. For instance, 0:="Abc" means that in the variable 0 is "Abc", and =:0 means retrieves the value of the variable 0. For instance, the len(%0) ? ( 0:=(%1+%2) ? currency(=:0) else `` ) : `` gets the sum between second and third column in currency format if it is not zero, and only if the first column is not empty. As you can see you can use the variables to avoid computing several times the same thing ( in this case the sum %1 and %2 .