priegle / steal

S-expression syntax sugar for Algorand TEAL contracts

sTEAL

sTEAL provides syntactic sugar for Algorand TEAL contracts, embedded in Scheme.

Use

Basic

Let's say we have the following sTEAL contract code:

(define sample '(= (txn Sender)
                   (txn Receiver)))

We can use the sTEAL compiler stealc to make TEAL assembly code. If we have the following code in example.rkt

#lang racket
(require "stealc.rkt")

(define sample '(= (txn Sender)
                   (txn Receiver)))

(displayln (stealc sample))

then running this program produces

$ racket example.rkt
txn Sender
txn Receiver
==

Template arguments

sTEAL can be used to make templates for TEAL contracts.

#lang racket
(require "stealc.rkt")

(define sample '(= (addr TMPL_RCV)
                   (txn Receiver)))

(displayln (stealc sample))

produces

addr TMPL_RCV
txn Receiver
==

To instantiate the templates with conrete values, use stealc-bind:

#lang racket
(require "stealc.rkt")

(define sample '(= (addr TMPL_RCV)
                   (txn Receiver)))

(define args
  '((TMPL_RCV "YC3XWSU3EUISB6N4EOGW5NYEMDSSWPGPMN3ZOKD33UDKPNK2HIXYPFLVXQ")))

(displayln (stealc (stealc-bind sample args)))

produces

addr YC3XWSU3EUISB6N4EOGW5NYEMDSSWPGPMN3ZOKD33UDKPNK2HIXYPFLVXQ
txn Receiver
==

Notes

Variable-length arguments

Certain symbols, such as and, compile into TEAL expressions that accept a variable number of arguments.

'(and (= (+ (txn FirstValid) (txn LastValid)) 500)
      (= arg_0 (byte base64 "uFVEhjBpkpKQ8sZaau0qsDsf0eW3oXFEn1Ar5o39vkk="))
      (> (txn Fee) (int TMPL_FEE)))

compiles into

txn FirstValid
txn LastValid
+
int 500
==
arg_0
byte base64 uFVEhjBpkpKQ8sZaau0qsDsf0eW3oXFEn1Ar5o39vkk=
==
&&
txn Fee
int TMPL_FEE
>
&&

Short-circuiting

Note that the and and or operators do not short-circuit as they do in Scheme.

The if symbol produces TEAL code which behaves similarly to Scheme's if special form.

'(if (= (global GroupSize) 1)
     (= (txn GroupIndex) 6)
     (< (txn Amount) 500))

compiles into

global GroupSize
int 1
==
bnz label0
txn Amount
int 500
<
int 1
bnz label1
label0:
txn GroupIndex
int 6
==
label1:

The labels produced in such a way are all unique.