Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations Wanet Telecoms Ltd on being selected by the Tek-Tips community for having the most helpful posts in the forums last week. Way to Go!
How can I analsys a expression
- Thread starter viettla
- Start date
- Thread starter
- #3
Mike Gagnon
Programmer
viettla
It is unclear what you are trying to achieve, what do you mean by "so I need analsys expression for solving nest expression (expression in expression)"
Mike Gagnon
If you want to get the best response to a question, please check out FAQ184-2483 first.
It is unclear what you are trying to achieve, what do you mean by "so I need analsys expression for solving nest expression (expression in expression)"
Mike Gagnon
If you want to get the best response to a question, please check out FAQ184-2483 first.
- Thread starter
- #5
Mike,
Im sorry about my English
My app allow users can define a field as a calculated field or an expression I need to parse that expression. Which does expression include fields name, constants , operators and other expression ?
How can I do this ?
thank's alot
Viet
Im sorry about my English
My app allow users can define a field as a calculated field or an expression I need to parse that expression. Which does expression include fields name, constants , operators and other expression ?
How can I do this ?
thank's alot
Viet
Hi viettla,
If I understand you correctly, you have to make a lot of DO..CASE, or you can use table and put in every expression that will be used by user.
This code is just for a starter (you need a LOT more code than this)
cExpression = This.Value
If !empty(cExpression)
nError = 0
On error nError = error()
= evaluate(cExpression) && test the expression
If (nError == 1300) && something wrong in expression
cExpression = alltrim(cExpression) + ')'
nError = 0
= evaluate(cExpression)
endif
If (nError == 0)
*** Check the expression against the table
* ...
*
If (nError == 0)
nValue = evaluate(cExpression)
endif
endif
On error
endif
Hope it helps a little
-- AirCon --
If I understand you correctly, you have to make a lot of DO..CASE, or you can use table and put in every expression that will be used by user.
This code is just for a starter (you need a LOT more code than this)
cExpression = This.Value
If !empty(cExpression)
nError = 0
On error nError = error()
= evaluate(cExpression) && test the expression
If (nError == 1300) && something wrong in expression
cExpression = alltrim(cExpression) + ')'
nError = 0
= evaluate(cExpression)
endif
If (nError == 0)
*** Check the expression against the table
* ...
*
If (nError == 0)
nValue = evaluate(cExpression)
endif
endif
On error
endif
Hope it helps a little
-- AirCon --
As a suggestion, use a delimiter in the expression around each field description, something like:
[Unit Price] * [Quantity Bought] * ([Sales Tax Percent] + 1)
Then, you can simply SCAN through a table that lists the fields, or hard code the fields, like this (assuming lcExpr contains the above pseudo-expression):
Then you can check if it's valid:
IF TYPE(lcVFPExpr)='N'
* Yup, It's valid!!
ENDIF
and just use macro replacement or EVAL() to evaluate it:
lnAmt = &lcVFPExpr
* or
lnAmt = EVAL(lcVFPExpr)
[Unit Price] * [Quantity Bought] * ([Sales Tax Percent] + 1)
Then, you can simply SCAN through a table that lists the fields, or hard code the fields, like this (assuming lcExpr contains the above pseudo-expression):
Code:
lcVFPExpr = lcExpr
lcVFPExpr = STRTRAN(lcVFPExpr,'[Unit Price]', 'orderTable.UnitPrice')
lcVFPExpr = STRTRAN(lcVFPExpr,'[Quantity Bought]', 'orderTable.Qty')
lcVFPExpr = STRTRAN(lcVFPExpr,'[Sales Tax Percent]', '0.06')Then you can check if it's valid:
IF TYPE(lcVFPExpr)='N'
* Yup, It's valid!!
ENDIF
and just use macro replacement or EVAL() to evaluate it:
lnAmt = &lcVFPExpr
* or
lnAmt = EVAL(lcVFPExpr)
- Status
