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| ELZED | Documentation | The Details | API |
| lzReadExpOpThe lzReadExpOp function establishes a new expression-based operator. long lzReadExpOp(| | char cScope, | | // the scope of the new operator | | | const char* szOperatorName, | | // the scope of the new operator | | | const char* szOperatorType, | | // the type of the new operator | | | const char* szReturnType, | | // the type of the value returned | | | const char* szParmList, | | // the list of operator parameters | | | const char* szPrecedenceOp, | | // an operator with the same precedence | | | const char* szFilePathName | | // the path to the expression file |
Parameters| cScope | | | A character code indicating the scope of the new operator. The character code must be one of the following values:
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Code
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Constant
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Meaning |
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'C'
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kCosmicScope
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Available in all contexts |
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'G'
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kGlobalScope
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Available in current context only |
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| szOperatorName | | | A null-terminated character string containing the name of the new expression-based operator. Must be unique within the indicated scope. |
| szOperatorType | | | A null terminated string containing the type of the new expression-based operator. Four type value constants are provided for your use:
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Type Value
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Constant
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Meaning |
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"prefix"
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kOpPrefix
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Operator before parms, like 'tan' or 'abs' |
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"infix"
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kOpInfix
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Operator between parms, like '+' or '=' |
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"postfix"
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kOpPostfix
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Operator after parms (rare), like post-increment '++' |
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"nofix"
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kOpNofix
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Operator without parms, like 'true' and 'pi' |
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| szReturnType | | | A pointer to a null-terminated character string containing the return type.
An Elzed expression operator may return one of the following types:
Type |
Description |
number |
a double precision numeric value |
string |
a null-terminated character string |
boolean |
a char value equal to zero (FALSE) or the current value representing boolean TRUE |
void |
no return value |
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| szParmList | | | A string list of parameter type/name pairs separated by commas.
The following parameter types are allowed:
Type |
Description |
number |
a double precision numeric value |
string |
a null-terminated character string |
boolean |
a char value equal to zero (FALSE) or the current value representing boolean TRUE |
Parameter types and names are case sensitive.
If the proposed operator has no parameters, szParmList should be NULL. |
| szPrecedenceOp | | | A character string containing an operator symbol. When successfully defined, the new expression operator will have the same precedence as this operator. |
| szFilePathName | | | A character string containing the path to the text file containing the expression which will be evaluated when the new operator is invoked. For recursive or circular definitions, this parameter will be NULL. |
Return Value| | Returns an Elzed error code. If the operator is successfully defined, returns "No Error". Returns a non-zero Elzed error code if not successful. Call lzGetLastErrorText to determine the reason for the failure. |
Remarks| | Available in both Visual C++ and Visual Basic.
Parameters passed to expression operators are considered to be at "local" scope. This means that parameters with the same names as variables at global or cosmic scope will effectively hide those variables. They will not be accessable within the operator expression.
Complete recursive and circular operator definitions with a call to lzDefineExpOpStr. |
Versions| | Introduced in Elzed 1.0.0
Modified in Elzed 2.3.1 -- "current list separator" is now "comma"
Modified in Elzed 2.4.0 -- String (char*) parameters are now declared const. | | | This page describes the version of lzReadExpOp active in Elzed 2.5.0 (222: 2.5.0) |
See Also |
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