Module swissknife

Expand description

GenApi formula parser and evaluator.

Covers the expression language used by <SwissKnife>, <IntSwissKnife>, <Converter> and <IntConverter> nodes:

Arithmetic: + - * / % and ** for power
Comparison: < <= > >=, = (equality) and <> (inequality)
Logical: && ||
Bitwise: & | ^ ~ << >>
Ternary: condition ? then : else
Functions: SGN NEG ATAN SIN COS TAN ABS EXP LN LG SQRT TRUNC ROUND FLOOR CEIL ASIN ACOS, plus the constants E and PI

Two details trip up implementations that reach for a C-like grammar, and both appear in the majority of real vendor descriptions:

= is equality, <> is inequality. There is no assignment in the language, so = is never ambiguous. == and != are accepted as tolerated aliases.
Integer formulas evaluate in i64, not f64. IntSwissKnife and IntConverter use EvalMode::Integer, where / truncates and 64-bit register values stay exact. Evaluating (HIGH << 32) | LOW in f64 silently loses the low bits.

Operator precedence and the integer/float promotion rules follow the GenApi specification, cross-checked against the reference implementation in aravis (src/arvevaluator.c: arv_evaluator_token_infos for precedence, the integer_mode branches of arv_evaluator_evaluate for promotion).

Structs§

ParseError: Error produced while parsing a GenApi formula.

Enums§

AstNode: Parsed GenApi formula represented as an abstract syntax tree.
BinaryOp: Binary operator kinds supported by the GenApi formula language.
EvalError: Error produced while evaluating a GenApi formula.
EvalMode: Arithmetic mode for a formula.
UnaryOp: Unary operator kinds supported by the GenApi formula language.
Value: Numeric value flowing through a GenApi formula.

Functions§

builtin_constant: Value of a GenApi built-in constant, if name denotes one.
collect_identifiers: Collect all variable identifiers referenced by the AST.
evaluate: Evaluate an AstNode using the provided variable resolver.
is_builtin_constant: Whether name denotes a GenApi built-in constant.
parse_expression: Parse a GenApi formula into an AstNode.
substitute: Replace variable references with sub-expressions.