Function MakeMap

parser/macro.go:497–526

MakeMap expands the input call arguments into a comprehension that transforms each element in the input to produce an output list. There are two call patterns supported by map: .map( , ) .map( , , ) In the second form only i

(eh ExprHelper, target ast.Expr, args []ast.Expr)

// In the second form only iterVar values which return true when provided to the predicate expression
// are transformed.
func MakeMap(eh ExprHelper, target ast.Expr, args []ast.Expr) (ast.Expr, *common.Error) {
	v, found := extractIdent(args[0])
	if !found {
		return nil, eh.NewError(args[0].ID(), "argument is not an identifier")
	}
	accu := eh.AccuIdentName()
	if v == accu || v == AccumulatorName {
		return nil, eh.NewError(args[0].ID(), "iteration variable overwrites accumulator variable")
	}

	var fn ast.Expr
	var filter ast.Expr

	if len(args) == 3 {
		filter = args[1]
		fn = args[2]
	} else {
		filter = nil
		fn = args[1]
	}

	init := eh.NewList()
	condition := eh.NewLiteral(types.True)
	step := eh.NewCall(operators.Add, eh.NewAccuIdent(), eh.NewList(fn))

	if filter != nil {
		step = eh.NewCall(operators.Conditional, filter, step, eh.NewAccuIdent())
	}
	return eh.NewComprehension(target, v, accu, init, condition, step, eh.NewAccuIdent()), nil
}

// MakeFilter expands the input call arguments into a comprehension which produces a list which contains
// only elements which match the provided predicate expression: