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)
1. Introduction

2. License

3. History

4. The Core Language

4.1 Base Types
4.1.1 Symbols
4.1.2 Strings
4.1.3 Numbers
4.2 Function Applications
4.3 The Top Level
4.4 Arithmetic
4.5 Comments

4.6 Sequences

4.6.1 Lists
4.6.2 Tuples
4.6.3 Vectors

4.7 lambda and let
4.8 Global Assignments
4.9 Higher Order Functions
4.10 Lazy Evaluation
4.11 I/O
4.12 Loading Files
4.13 Streams
4.14 Exceptions
4.15 Hashing
4.16 Property Lists
4.17 Eval

5 Defining Functions

5.1 Partial Functions
5.2 List Handling Functions
5.3 String Handling Functions
5.4 Tuple Handling Functions
5.5 Vector Handling Functions
5.6 Guards
5.7 Backtracking
5.8 Writing in Kλ
5.9 Macros

6. Packages

7. Shen-YACC

7.1 Recognisor Generator
7.2 Semantic Actions

8. Shen Prolog

8.1 Sample Programs

9. Types

9.1 Types and Constructors
9.2 Functions and Types
9.3 Synonyms

10 Sequent Calculus

10.1 Recursive Types

10.2 Exotic Types

10.2.1 Dependent Types
10.2.2 Negative Types
10.2.3 Subtypes
10.2.4 The Type of All Sets

11 Glossary of Functions

12 The Syntax of Shen

Built by Shen Technology (c) Mark Tarver, September 2021