shhyou

Racket tips and tricks

These are extracted from discussions I triggered on the Racket Slack. Thanks to everyone who participated in the discussion threads! :-)

Conversion to boolean

Use (and value #t) to convert a value to its boolean equivalent.

Entering a module in the Racket REPL

shhyou

#lang racket/base

(require (for-syntax racket/base
                     syntax/parse)
         racket/stxparam)

;; (bind x-id e-expr)
;; Bind x-id to some string in e-expr
;; Expands to a expression that constructs a hash
;; table storing e-expr in a field

shhyou

#lang racket/base

(require (for-syntax racket/base)
         syntax/parse/define)

(let ()
  (define-syntax-parse-rule (define-sum S)
    (define (S n)
      (if (= n 0) 0 (+ n (S (- n 1))))))

shhyou

#lang racket/base

(require racket/match)

(provide current-solver-path
         call-with-solver
         solve)

(define current-solver-path (make-parameter (find-executable-path "z3")))

shhyou

import Control.Applicative
import Control.Monad

main = putStrLn "Hello, World!"

data Void
data Cont r a = Cont ((a -> r) -> r)

unCont (Cont m) = m

shhyou

#lang racket/base

(require (for-syntax racket/base
                     racket/syntax
                     syntax/parse))

(define-syntax (define-constant stx)
  (syntax-parse stx
    [(_ name:id
        (~optional (~and #:evaluate evaluate-kw))

shhyou

#lang pollen

◊(define lam "\\lambda")

$◊lam x . \, ◊mathit{function \, body}$

◊textnormal{◊textbf unapplied text command}

shhyou

#lang pollen

◊(define lam "\\lambda")

$◊lam_k\\nabla g_k(x)$

shhyou

#lang racket/base

(require racket/generator
         racket/stream
         racket/sequence)

(define (make-iter-gen xs ys)
  (generator
   ()
   (for ([x (in-list xs)])

shhyou

;; Exporting free identifier table operations that close over a global map
#lang racket/base

(require racket/list
         syntax/id-table)

(provide env-ref env-has-id? env-add!)

(define id-table (make-free-id-table))