Module expr 

The restricted expression grammar and parser.

The parser produces an AST. Function resolution and evaluation live in the engine crate and use exactly the same registry and validation as the typed calculate path. Nothing here evaluates Rust, JavaScript, shell commands, imports, or remote code.

Grammar (whitespace-insensitive; // line comments and /* */ block comments are supported):

expr        := or_expr
or_expr     := and_expr (('or' | '||') and_expr)*
and_expr    := not_expr (('and' | '&&') not_expr)*
not_expr    := ('not' | '!') not_expr | comparison
comparison  := additive (comp_op additive)+          // chained, e.g. 0 < x < 1
additive    := multiplicative (('+' | '-') multiplicative)*
multiplicative := unary (('*' | '/' | '%') unary)*
unary       := ('-' | '+') unary | power
power       := primary ('^' unary)?                  // right associative
primary     := NUMBER | STRING | 'true' | 'false' | IDENT
             | IDENT ('.' IDENT)+ '(' arguments? ')'
             | IDENT '(' arguments? ')'             // unqualified calls rejected
             | '(' expr ')' | '[' array ']' | '{' record '}'
arguments   := argument (',' argument)*
argument    := (IDENT '=')? expr
array       := expr (',' expr)* ','?
record      := (IDENT | STRING) ':' expr (',' ...)* ','?

Precedence (loosest to tightest): or, and, not, comparison, + -, * / %, unary sign, ^. Exponentiation binds tighter than unary minus, so -2^2 == -4, and is right associative, so 2^3^2 == 2^9.

Structs

CallArg

Enums

BinaryOp

CompareOp

Expr

UnaryOp

Functions

parse_expression

Parse a restricted expression. This performs no function resolution.