use proc_macro::TokenStream;
use syn::{LitInt, parse::{Parse, ParseStream, Result as SynResult}, parse_macro_input};
struct CollectionLen {
len: usize,
}
impl Parse for CollectionLen {
fn parse(input: ParseStream) -> SynResult<CollectionLen> {
input.parse::<LitInt>().map(|litint| litint.base10_parse::<usize>())?.map(|len| CollectionLen { len })
}
}
#[proc_macro]
pub fn impl_ops_arr(input: TokenStream) -> TokenStream {
let CollectionLen { len } = parse_macro_input!(input as CollectionLen);
let self_destructure = (0..len).map(|e| format!("e_{}", e)).collect::<Vec<_>>();
let mut expanded = String::new();
if len > 1 {
let decimpl = format!(
"impl<T> OrdesPop for [T; {len}] {{\n \
type Newlen = [T; {len_less_1}];\n \
type Output = T;\n\n \
fn pop(self) -> (Self::Newlen, Self::Output) {{\n \
let [{self_destructure}] = self;\n \
([{self_destructure_less_end}], {last})\n \
}}\n\
}}\n\n
impl<T> OrdesRest for [T; {len}] {{\n \
type Newlen = [T; {len_less_1}];\n \
type Output = T;\n\n \
fn rest(self) -> (Self::Newlen, Self::Output) {{\n
let [{self_destructure}] = self;\n \
([{self_destructure_less_start}], {first})\n \
}}\n\
}}\n",
len = len,
len_less_1 = len - 1,
self_destructure = self_destructure.join(", "),
self_destructure_less_end = self_destructure[..len - 1].join(", "),
last = self_destructure[len - 1],
self_destructure_less_start = self_destructure[1..].join(","),
first = self_destructure[0]
);
expanded.push_str(&decimpl);
} else if len == 1 {
let decimpl = "\
impl<T> OrdesPop for [T; 1] {\n \
type Newlen = ();\n \
type Output = T;\n\n \
fn pop(self) -> (Self::Newlen, T) {\n \
let [e_0] = self;\n \
((), e_0)\n \
}\n\
}\n\n\
impl<T> OrdesRest for [T; 1] {\n \
type Newlen = ();\n \
type Output = T;\n\n \
fn rest(self) -> (Self::Newlen, T) {\n \
let [e_0] = self;
((), e_0)\n \
}\n\
}\n\
";
expanded.push_str(decimpl);
}
if len < std::usize::MAX {
let incimpl = format!(
"impl<T> OrdesPush<T> for [T; {len}] {{\n \
type Output = [T; {len_plus_1}];\n\n \
fn push(self, value: T) -> Self::Output {{\n \
let [{self_destructure}] = self;\n \
[{self_destructure}, value]\n \
}}\n\
}}\n\n\
impl<T> OrdesCons<T> for [T; {len}] {{\n \
type Output = [T; {len_plus_1}];\n\n \
fn cons(self, value: T) -> Self::Output {{\n \
let [{self_destructure}] = self;\n \
[value, {self_destructure}]\n \
}}\n\
}}\n",
len = len,
len_plus_1 = len + 1,
self_destructure = self_destructure.join(", "),
);
expanded.push_str(&incimpl);
}
expanded.parse().unwrap()
}
#[proc_macro]
pub fn impl_ops_tuple(input: TokenStream) -> TokenStream {
let CollectionLen { len } = parse_macro_input!(input as CollectionLen);
let self_type_params = (0..len).map(|t| format!("T{}", t)).collect::<Vec<_>>();
let self_destructure = (0..len).map(|e| format!("e_{}", e)).collect::<Vec<_>>();
let mut expanded = String::new();
if len > 1 {
let decimpl = format!(
"impl<{self_types}> OrdesPop for ({self_types}) {{\n \
type Newlen = ({self_types_less_last});\n \
type Output = {last_type};\n\n \
fn pop(self) -> (Self::Newlen, {last_type}) {{\n \
let ({self_destructure}) = self;\n \
(({self_destructure_less_last}), {last})\n \
}}\n\
}}
impl<{self_types}> OrdesRest for ({self_types}) {{\n \
type Newlen = ({self_types_less_first});\n \
type Output = {first_type};\n\n \
fn rest(self) -> (Self::Newlen, {first_type}) {{\n \
let ({self_destructure}) = self;\n \
(({self_destructure_less_first}), {first})
}}\n\
}}\n",
self_types = self_type_params.join(", "),
self_types_less_last = self_type_params[..len - 1].join(", "),
last_type = self_type_params[len - 1],
self_destructure = self_destructure.join(", "),
self_destructure_less_last = self_destructure[..len - 1].join(", "),
last = self_destructure[len - 1],
self_types_less_first = self_type_params[1..].join(", "),
first_type = self_type_params[0],
self_destructure_less_first = self_destructure[1..].join(", "),
first = self_destructure[0]
);
expanded.push_str(&decimpl);
} else if len == 1 {
let decimpl = "\
impl<T0> OrdesPop for (T0,) {\n \
type Newlen = ();\n \
type Output = T0;\n\n \
fn pop(self) -> (Self::Newlen, T0) {\n \
let (e_0,) = self;\n \
((), e_0)\n \
}\n\
}\n\n\
impl<T0> OrdesRest for (T0,) {\n \
type Newlen = ();\n \
type Output = T0;\n\n \
fn rest(self) -> (Self::Newlen, T0) {\n \
let (e_0,) = self;\n \
((), e_0)\n \
}\n\
}\n\
";
expanded.push_str(decimpl);
}
if len < std::usize::MAX && len > 1 {
let incimpl = format!(
"impl<{self_types}, {extra_type}> OrdesPush<{extra_type}> for ({self_types}) {{\n \
type Output = ({self_types}, {extra_type});\n\n \
fn push(self, value: {extra_type}) -> Self::Output {{\n \
let ({self_destructure}) = self;\n \
({self_destructure}, value)\n \
}}\n\
}}\n\n\
impl<{self_types}, {extra_type}> OrdesCons<{extra_type}> for ({self_types}) {{\n \
type Output = ({extra_type}, {self_types});\n\n \
fn cons(self, value: {extra_type}) -> Self::Output {{\n \
let ({self_destructure}) = self;\n \
(value, {self_destructure})\n \
}}\n\
}}\n",
self_types = self_type_params.join(", "),
extra_type = format!("T{}", len),
self_destructure = self_destructure.join(", "),
);
expanded.push_str(&incimpl);
} else if len == 1 {
let incimpl = "\
impl<T0, T1> OrdesPush<T1> for (T0,) {\n \
type Output = (T0, T1);\n\n \
fn push(self, value: T1) -> Self::Output {\n \
let (e_0,) = self;\n \
(e_0, value)\n \
}\n\
}\n\n\
impl<T0, T1> OrdesCons<T1> for (T0,) {\n \
type Output = (T1, T0);\n\n \
fn cons(self, value: T1) -> Self::Output {\n \
let (e_0,) = self;\n \
(value, e_0)\n \
}\n\
}\
";
expanded.push_str(incimpl);
}
expanded.parse().unwrap()
}