Scheme interpreter In C++
Make use of modern C++ and RAII.
Usage
1 ]=> 1
;Value: 1
1 ]=> (+ 1 2)
;Value: 3
1 ]=> (define x 1)
;Value: x
1 ]=> (+ x 1)
;Value: 2
1 ]=> (define square (lambda (x) (* x x)))
;Value: square
1 ]=> (square 2)
;Value: 4
1 ]=> (if (> x 2) x 2)
;Value: 2
1 ]=> (cons 1 2)
;Value: '(1 2)
1 ]=> (car (cons 1 2))
;Value: 1
1 ]=> (cdr (cons 1 2))
;Value: 2Spec
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if = (if predicate consequent alternative)
define = (define symbol expression)
quotation = (quote expr)
lambda = (lambda (symbol1 symbol2 ...) expr1 expr2 ...)
Special = (if, define, quotation, lambda)
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Primitive = (+ - * / ...)
Procedure = User-defined
Function = (Procedure, Primitive)
Call = (Function expr1 expr2 ...)
--------------------------------------------------------------
List = (Call, Special)
--------------------------------------------------------------
Symbol = string
Number = double
Atom = (Symbol, Number)
--------------------------------------------------------------
Expr = (List, Atom)
--------------------------------------------------------------
Env = mapSteps
Program => Scanner(Tokens) => Parser(AST) => Eval(Result)
Scanner
Also called lexical analysis, it scans all the source code, and get tokens.
Example:
"var average = (min + max) / 2;" ->:
"var" "average" "=" "(" "min" "+" "max" ")" "/" "2" ";"
Parser
Get Abstract syntax tree. And get syntax errors.
Evaluation
Retrieve calculation result from AST.
Reference
- cxxopts: A lightweight C++ command line option parser
- craftinginterpreters: Lox
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