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[QUESTION] Using Expr.Function with function type arguments #858
Description
Hi @antonmedv!
I'm trying to port some of the functions provided by the lo package to have more capabilities of collection types manipulation. But I'm having a hard time trying to represent the function argument as an expression. It compiles but throws a runtime error.
Expr version: v1.17.5
Go version: go1.24.9 linux/amd64
Example of the Expr function:
import (
"github.com/expr-lang/expr"
"github.com/samber/lo"
)
const sliceToMapFuncParamsLen = 2
func sliceToMapFunc() expr.Option {
return expr.Function(
"SliceToMap",
func(params ...any) (any, error) {
if len(params) != 2 {
return nil, invalidParametersNumberError("SliceToMap", sliceToMapFuncParamsLen, len(params))
}
slice, ok := params[0].([]any)
if !ok {
return nil, invalidParameterTypeError("SliceToMap", 0, "[]any", TypeOf(params[0]))
}
fn, ok := params[1].(func(any) (string, any))
if !ok {
return nil, invalidParameterTypeError("SliceToMap", 1, "func(any) (string, any)", TypeOf(params[1]))
}
return lo.SliceToMap(slice, fn), nil
},
new(func([]any, func(any) (string, any)) (any, error)),
)
}
Expression examples:
SliceToMap(.data, {{string(#.key):#.value}})
SliceToMap(.data, {#.key,#.value})
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