https://github.com/athos/type-infer
A Clojure utility to inspect static types inferred by the Clojure compiler
https://github.com/athos/type-infer
clojure macros static-types type-inference
Last synced: 7 months ago
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A Clojure utility to inspect static types inferred by the Clojure compiler
- Host: GitHub
- URL: https://github.com/athos/type-infer
- Owner: athos
- License: other
- Created: 2021-01-27T15:18:15.000Z (about 5 years ago)
- Default Branch: main
- Last Pushed: 2023-08-22T16:21:43.000Z (over 2 years ago)
- Last Synced: 2025-04-14T12:57:59.548Z (10 months ago)
- Topics: clojure, macros, static-types, type-inference
- Language: Clojure
- Homepage:
- Size: 33.2 KB
- Stars: 23
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
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README
# type-infer
[](https://clojars.org/dev.athos/type-infer)
A Clojure utility to inspect static types inferred by the Clojure compiler
## Installation
Add the following to your `deps.edn` / `project.clj`:
- `deps.edn`
```
{dev.athos/type-infer {:mvn/version "0.1.2"}}
```
- `project.clj`
```
[dev.athos/type-infer "0.1.2"]
```
## Usage
### `infer`
The `infer` macro tells us the static type of the given expression inferred
by the Clojure compiler:
```clojure
(require '[type-infer.core :refer [infer]])
(infer 42) ;=> long
(infer false) ;=> java.lang.Boolean
(infer "foo") ;=> java.lang.String
```
It can take an arbitrary expression and returns its static type as long as
the Clojure compiler can infer:
```clojure
(infer (not false)) ;=> java.lang.Boolean
(infer (/ 1 2)) ;=> java.lang.Number
(infer (if (even? 2) :even :odd)) ;=> clojure.lang.Keyword
(infer (let [x 2 y (inc x)] (* x y))) ;=> long
(infer (fn [x] x)) ;=> clojure.lang.AFunction
```
Otherwise (i.e. the compiler failed to infer the static type of the given expression),
`infer` returns `nil`:
```clojure
(infer (identity 42)) ;=> nil
(infer (if (even? 2) "foo" false)) ;=> nil
(infer cons) ;=> nil
```
The `infer` macro is mainly intended to be used for performance tuning, and is especially
useful for removing reflection warnings and taking full advantage of primitive types.
In most cases, `infer` per se is difficult to use in your function or macro.
If you want to use it in your macro, it's highly recommend to use `infer-type` below instead.
### `infer-type`
The `infer-type` fn takes two arguments: The first one is the implicit macro argument
`&env` and the second one is a symbol. To get `&env`, you need to call `infer-type` in a macro:
```clojure
(require '[type-infer.core :as ty])
(defmacro my-infer-type* [sym]
(ty/infer-type &env sym))
(def ^String s "foo")
(my-infer-type s) ;=> java.lang.String
(let [x 42]
(my-infer-type x)) ;=> long
```
Note that `infer-type` only accepts a symbol as its second argument.
If you want to pass arbitrary expression to it, you'll need to pass the expression
via an extra `let` form like the following:
```clojure
(defmacro my-infer-type [x]
`(let [x# ~x]
(my-infer-type* x#)))
(my-infer-type (fn [x] x)) ;=> clojure.lang.AFunction
```
Note also that due to the above limitation, the target expression of the type inference
may be evaluated at most once. This means that it is impossible (or difficult at best)
to implement macros using `infer-type` such that the input expression is never evaluated
in the expanded form.
## Practical use
Examples of practical use of the library can be found in the following projects:
- [sweet-array](https://github.com/athos/sweet-array)
- [power-dot](https://github.com/athos/power-dot)
## License
Copyright © 2021 Shogo Ohta
This program and the accompanying materials are made available under the
terms of the Eclipse Public License 2.0 which is available at
http://www.eclipse.org/legal/epl-2.0.
This Source Code may also be made available under the following Secondary
Licenses when the conditions for such availability set forth in the Eclipse
Public License, v. 2.0 are satisfied: GNU General Public License as published by
the Free Software Foundation, either version 2 of the License, or (at your
option) any later version, with the GNU Classpath Exception which is available
at https://www.gnu.org/software/classpath/license.html.