fpExprPars unit

This unit implements an expression parser and evaluator that supports a wide variety of data types, mathematical operations, and built-in functions. It provides the infrastructure for parsing and evaluating mathematical expressions with support for variables, functions, and complex data types.

The parser supports the following features:

• Multiple data types: integers, floats, strings, booleans, dates, and currency
• Standard mathematical operators: +, -, *, /, mod, power
• Comparison operators: =, <>, <, >, <=, >=
• Logical operators: and, or, xor, not
• Built-in mathematical, string, and date/time functions comparable to what exists in the SysUtils unit.
• Variable and function definitions
• Conditional expressions (if-then-else)
• Aggregate functions for data processing

The unit is designed to be extensible, allowing custom functions and variables to be registered with the parser for specialized applications.

Classes and records

EExprParser	class	Expression parser exception class
EExprScanner	class	Exception class for scanner errors
TAggregateAvg	class	Internally used class for average aggregate functions
TAggregateCount	class	Internally used class for count aggregate functions
TAggregateExpr	class	Internally used Base class for aggregate expressions
TAggregateMax	class	Internally used class for maximum aggregate functions
TAggregateMin	class	Internally used class for minimum aggregate functions
TAggregateSum	class	Internally used class for sum aggregate functions
TCaseOperation	class	Internally used class for case-when conditional operations
TCurrencyToDateTimeNode	class	Internally used class for converting currency to datetime
TCurrencyToFloatNode	class	Internally used class for converting currency to float
TExprBuiltInManager	class	Class for managing built-in functions and variables in expressions
TFloatToCurrencyNode	class	Internally used class for converting float to currency
TFloatToDateTimeNode	class	Internally used class for converting float to datetime
TFPAddOperation	class	Internally used class for addition operations
TFPBinaryAndOperation	class	Internally used class for binary AND logical operation
TFPBinaryOperation	class	Internally used class for binary operations with left and right operands
TFPBinaryOrOperation	class	Internally used class for binary OR logical operation
TFPBinaryXOrOperation	class	Internally used class for binary XOR logical operation
TFPBooleanOperation	class	Internally used class for boolean operations in expressions
TFPBooleanResultOperation	class	Internally used class for operations that result in boolean values
TFPBuiltInExprIdentifierDef	class	Class for built-in expression identifier definitions
TFPConstExpression	class	Internally used class for constant value expressions
TFPConvertNode	class	Internally used class for type conversion operations
TFPDivideOperation	class	Internally used class for division operations
TFPEqualOperation	class	Internally used class for equality comparison operations
TFPExpressionParser	class	Class for parsing and evaluating mathematical expressions
TFPExpressionResult	record	Record representing the result of expression evaluation
TFPExpressionScanner	class	Class for tokenizing expression strings into parser tokens
TFPExprFunction	class	Internally used class for representing function calls in expression trees
TFPExprIdentifierDef	class	Class for defining identifiers in expressions
TFPExprIdentifierDefs	class	Collection class for expression identifier definitions
TFPExprIdentifierNode	class	Internally used class for identifier nodes in expression trees
TFPExprNode	class	Class for representing nodes in expression trees
TFPExprVariable	class	Internally used class for variable expression nodes
TFPFunctionCallBack	class	Internally used class for callback-based function expressions
TFPFunctionEventHandler	class	Internally used class for event-based function expressions
TFPGreaterThanEqualOperation	class	Internally used class for greater-than-or-equal comparison operations
TFPGreaterThanOperation	class	Internally used class for greater-than comparison operations
TFPLessThanEqualOperation	class	Internally used class for less-than-or-equal comparison operations
TFPLessThanOperation	class	Internally used class for less-than comparison operations
TFPModuloOperation	class	Internally used class for modulo operations
TFPMultiplyOperation	class	Internally used class for multiplication operations
TFPNegateOperation	class	Internally used class for numeric negation operations
TFPNotNode	class	Internally used class for logical NOT operations
TFPOrderingOperation	class	Internally used class for ordering comparison operations
TFPPowerOperation	class	Internally used class for power/exponentiation operations
TFPSubtractOperation	class	Internally used class for subtraction operations
TFPUnaryOperator	class	Internally used class for unary operations with single operand
TFPUnequalOperation	class	Internally used class for inequality comparison operations
TIfOperation	class	Internally used class for conditional if-then-else operations
TIntConvertNode	class	Internally used class for integer conversion operations
TIntToCurrencyNode	class	Internally used class for converting integer to currency
TIntToDateTimeNode	class	Internally used class for converting integer to datetime
TIntToFloatNode	class	Internally used class for converting integer to float
TMathOperation	class	Internally used class for mathematical operations in expressions

Procedures and functions

ArgToFloat	function	Convert argument to float value
BuiltinIdentifiers	function	Get built-in identifiers manager
CharToResultType	function	Convert character to result type
RegisterStdBuiltins	procedure	Register standard built-in functions
ResultTypeName	function	Get name for result type
TokenName	function	Get name for token type

Types

PFPExpressionResult	type	Pointer to TFPExpressionResult record
TBuiltInCategories	set	Set of built-in function categories
TBuiltInCategory	enumeration	Type representing categories of built-in functions
TExprArgumentArray	type	Array type for expression arguments
TExprFloat	type	Type representing floating-point values in expressions
TExprParameterArray	type	Array type for function parameters in expressions
TFPBinaryOperationClass	type	Class reference type for TFPBinaryOperation
TFPBooleanResultOperationClass	type	Class reference type for TFPBooleanResultOperation
TFPExpressionParserClass	type	Class reference type for TFPExpressionParser
TFPExprFunctionCallBack	procedure type	Callback procedure type for function evaluation
TFPExprFunctionClass	type	Class reference type for TFPExprFunction
TFPExprFunctionEvent	procedure type	Event procedure type for function evaluation
TFPExprVariableCallBack	procedure type	Callback procedure type for variable evaluation
TFPExprVariableEvent	procedure type	Event procedure type for variable evaluation
TIdentifierEvent	procedure type
TIdentifierType	enumeration	Type representing different kinds of identifiers in expressions
TNumberKind	enumeration	Type representing different number formats that can be parsed
TResultType	enumeration	Type representing different result data types in expressions
TResultTypes	set	Set of result types
TTokenType	enumeration	Type representing different token types in expression parsing

Constants

AllBuiltIns	constant	Set of all built-in identifier categories
ttComparisons	constant	Set of token types used for comparison operations
ttDelimiters	constant	Set of token types used as operators and delimiters

Uses

• Classes
• SysUtils
• Contnrs