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repl.go
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repl.go
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package repl
import (
"bufio"
"fmt"
"io"
"monkey/evaluator"
"monkey/lexer"
"monkey/object"
"monkey/parser"
)
const PROMPT = ">> "
func Start(in io.Reader, out io.Writer) {
scanner := bufio.NewScanner(in)
env := object.NewEnvironment()
for {
fmt.Printf(PROMPT)
scanned := scanner.Scan()
if !scanned {
return
}
line := scanner.Text()
l := lexer.New(line)
p := parser.New(l)
program := p.ParseProgram()
if len(p.Errors()) != 0 {
printParserErrors(out, p.Errors())
continue
}
evaluated := evaluator.Eval(program, env)
if evaluated != nil {
io.WriteString(out, evaluated.Inspect())
io.WriteString(out, "\n")
}
}
}
const MONKEY_FACE = ` __,__
.--. .-" "-. .--.
/ .. \/ .-. .-. \/ .. \
| | '| / Y \ |' | |
| \ \ \ 0 | 0 / / / |
\ '- ,\.-"""""""-./, -' /
''-' /_ ^ ^ _\ '-''
| \._ _./ |
\ \ '~' / /
'._ '-=-' _.'
'-----'
`
func printParserErrors(out io.Writer, errors []string) {
io.WriteString(out, MONKEY_FACE)
io.WriteString(out, "Woops! We ran into some monkey business here!\n")
io.WriteString(out, " parser errors:\n")
for _, msg := range errors {
io.WriteString(out, "\t"+msg+"\n")
}
}