Documentation
¶
Overview ¶
Package expr implements a small expression language used by iterion's `compute` nodes and `when` edge clauses.
Grammar (informal):
expr := or
or := and ( "||" and )*
and := not ( "&&" not )*
not := "!" not | cmp
cmp := add ( ( "==" | "!=" | "<" | "<=" | ">" | ">=" ) add )?
add := mul ( ( "+" | "-" ) mul )*
mul := unary ( ( "*" | "/" | "%" ) unary )*
unary := "-" unary | primary
primary := number | string | bool | funcCall | path | "(" expr ")"
funcCall := IDENT "(" ( expr ( "," expr )* )? ")"
path := IDENT ( "." IDENT )*
The path namespaces recognized by the evaluator depend on the Context: `vars`, `input`, `outputs`, `artifacts`, `loop.<name>.{iteration,max,previous_output[.field]}`, and `run.{id}` are the standard ones.
Builtin functions: `length`, `concat`, `unique`, `contains`. See the builtins map below for signatures and semantics. Function calls are disambiguated from path lookups purely by the presence of `(` directly after the leading IDENT — there is no separate keyword set.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type AST ¶
type AST struct {
// contains filtered or unexported fields
}
AST is the parsed form of an expression. It is opaque outside the package.
func Parse ¶
Parse parses an expression string and returns its AST. Returns an error on malformed input. The returned AST can be evaluated many times against different contexts.
func (*AST) Eval ¶
Eval evaluates the AST against the context and returns the resulting value (typed as bool, int64, float64, string, or nil for absent paths).
func (*AST) EvalBool ¶
EvalBool evaluates and coerces the result to bool. Non-bool truthy values follow standard rules: nil → false, "" → false, 0 → false, others → true.
type Context ¶
type Context struct {
Vars func(path []string) interface{}
Input func(path []string) interface{}
Outputs func(path []string) interface{}
Artifacts func(path []string) interface{}
Loop func(path []string) interface{} // loop.<name>.<...>
Run func(path []string) interface{} // run.<...>
}
Context provides values that path expressions resolve against.
Each callback receives the dotted path *after* the namespace prefix and returns the resolved value (or nil if not found). The evaluator never inspects the structure beyond what the callback returns.
Source Files