Calculator Language Modules
H. Conrad Cunningham
24 November 2018
Copyright (C) 2017, 2018, H. Conrad Cunningham
Acknowledgements: I originally created these slides in Fall 2017 to accompany what is now Chapter 43, Calculator: Modular Structure, in the 2018 version of the textbook Exploring Languages with Interpreters and Functional Programming.
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Values module Values (Ch. 42)
Secret: specific representation for values supported by language
Environments module Environments (Ch. 42)
Secret: specific representation for environments used by interpreter
Abstract_Synax module AbSynCalc (Ch. 42)
Centralize definitions of abstract syntax
Evaluator module EvalCalc (Ch. 42)
Secret: implementation of language semantics
Lexical_analyzer module LexCalc common to both parsers (Ch.
44)
Secret: lexical structure of concrete language (identifiers, literal constants, operators, etc.)
Parser abstract module (Ch. 44)
Secret: how concrete syntax recognized and translated to abstract syntax
Prefix syntax Parser module ParsePrefixCalc
Infix syntax Parser module ParseInfixCalc{type=“text/plain”
Haskell IO program
Read an input from the command line.
If the input is an exit command, exit; else continue.
Evaluate the expression after parsing.
Print the resulting value.
Loop back to step 1.
Uses Parser and Evaluator modules
Separate versions
infix: InfixCalcREPL
prefix: PrefixCalcREPL
Expressons plus REPL commands :set,
:display, :quit
Modular structure for Calculator language interpreter
7 modules
cohesive units
secrets
abstract interfaces