The Top Level

4.3 The Top Level

TBoS p 34-35

The Shen top level is a read-evaluate-print loop as in all functional languages. When you start it up, you get something this (depending on release and platform).

Shen, copyright (C) 2010-2015 Mark Tarver
www.shenlanguage.org, Shen 30
running under Common Lisp, implementation: SBCL
port 3.1 ported by Mark Tarver


(0-) hello
hello

Each input is numbered starting with 0.

The top level has a feature borrowed from Unix of allowing past inputs to be repeated. !! repeats and evaluates the last input. !n repeats and evaluates the nth input. !s where s is a symbol repeats the last input whose leading function has s as a prefix. %n prints the nth input w.o. evaluation. %s prints the last expression entered whose prefix is s. % prints all expressions entered since the session began.

(0-) hello
hello

(1-) (* 7 8)
56

(2-) !1
(* 7 8)
56

(3-) !*
(* 7 8)
56

(4-) %*
1. (* 7 8)
2. (* 7 8)
3. (* 7 8)

4. The Core Language

4.6 Sequences

5 Defining Functions

6. Packages

7. Shen-YACC

8. Shen Prolog

9. Types

10 Sequent Calculus

10.2 Exotic Types