diff options
Diffstat (limited to 'users/fcuny/exp/monkey/pkg/lexer')
-rw-r--r-- | users/fcuny/exp/monkey/pkg/lexer/lexer.go | 152 | ||||
-rw-r--r-- | users/fcuny/exp/monkey/pkg/lexer/lexer_test.go | 125 |
2 files changed, 0 insertions, 277 deletions
diff --git a/users/fcuny/exp/monkey/pkg/lexer/lexer.go b/users/fcuny/exp/monkey/pkg/lexer/lexer.go deleted file mode 100644 index 3e98cf0..0000000 --- a/users/fcuny/exp/monkey/pkg/lexer/lexer.go +++ /dev/null @@ -1,152 +0,0 @@ -// Package lexer provides a lexer to the monkey language. -package lexer - -import "monkey/pkg/token" - -// Lexer represents the lexer -type Lexer struct { - input string - // current position in input - position int - // current reading position in input (after a char) - readPosition int - // current character under examination - ch byte -} - -// New returns a new lexer -func New(input string) *Lexer { - l := &Lexer{input: input} - l.readChar() - return l -} - -// Read the current character and advances our position in the input string. -func (l *Lexer) readChar() { - // if we've reached the end of the input, we set the current character to 0, - // which is the ASCII code for NUL. - if l.readPosition >= len(l.input) { - l.ch = 0 - } else { - l.ch = l.input[l.readPosition] - } - l.position = l.readPosition - l.readPosition++ -} - -func (l *Lexer) readIdentifier() string { - position := l.position - for isLetter(l.ch) { - l.readChar() - } - return l.input[position:l.position] -} - -func (l *Lexer) readNumber() string { - position := l.position - for isDigit(l.ch) { - l.readChar() - } - return l.input[position:l.position] -} - -// we don't care about white space characters, we skip them when we find them. -func (l *Lexer) skipWhitespace() { - for l.ch == ' ' || l.ch == '\t' || l.ch == '\n' || l.ch == '\r' { - l.readChar() - } -} - -// peekChar returns the character at position (which is the next charatecter), -// but does not increment `readPosition` and `position`. -// This is needed to read tokens that are composed of two characters (e.g. `==`). -func (l *Lexer) peekChar() byte { - if l.readPosition >= len(l.input) { - return 0 - } - return l.input[l.readPosition] -} - -// NextToken reads the next token from the lexer and returns the current token. -func (l *Lexer) NextToken() token.Token { - var tok token.Token - - l.skipWhitespace() - - switch l.ch { - case '=': - if l.peekChar() == '=' { - ch := l.ch - l.readChar() - literal := string(ch) + string(l.ch) - tok = token.Token{Type: token.EQ, Literal: literal} - } else { - tok = newToken(token.ASSIGN, l.ch) - } - case '+': - tok = newToken(token.PLUS, l.ch) - case '-': - tok = newToken(token.MINUS, l.ch) - case '!': - if l.peekChar() == '=' { - ch := l.ch - l.readChar() - literal := string(ch) + string(l.ch) - tok = token.Token{Type: token.NOT_EQ, Literal: literal} - } else { - tok = newToken(token.BANG, l.ch) - } - case '*': - tok = newToken(token.ASTERISK, l.ch) - case '/': - tok = newToken(token.SLASH, l.ch) - case '<': - tok = newToken(token.LT, l.ch) - case '>': - tok = newToken(token.GT, l.ch) - - case ';': - tok = newToken(token.SEMICOLON, l.ch) - case ',': - tok = newToken(token.COMMA, l.ch) - case '(': - tok = newToken(token.LPAREN, l.ch) - case ')': - tok = newToken(token.RPAREN, l.ch) - case '{': - tok = newToken(token.LBRACE, l.ch) - case '}': - tok = newToken(token.RBRACE, l.ch) - case 0: - tok.Literal = "" - tok.Type = token.EOF - default: - if isLetter(l.ch) { - tok.Literal = l.readIdentifier() - tok.Type = token.LookupIdent(tok.Literal) - return tok - } else if isDigit(l.ch) { - tok.Type = token.INT - tok.Literal = l.readNumber() - return tok - } else { - tok = newToken(token.ILLEGAL, l.ch) - } - - } - - l.readChar() - return tok -} - -func newToken(tokenType token.TokenType, ch byte) token.Token { - return token.Token{Type: tokenType, Literal: string(ch)} -} - -func isLetter(ch byte) bool { - return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch == '_' -} - -func isDigit(ch byte) bool { - return '0' <= ch && ch <= '9' -} diff --git a/users/fcuny/exp/monkey/pkg/lexer/lexer_test.go b/users/fcuny/exp/monkey/pkg/lexer/lexer_test.go deleted file mode 100644 index fdea1d3..0000000 --- a/users/fcuny/exp/monkey/pkg/lexer/lexer_test.go +++ /dev/null @@ -1,125 +0,0 @@ -package lexer - -import ( - "monkey/pkg/token" - "testing" -) - -func TestNextToken(t *testing.T) { - input := `let five = 5; -let ten = 10; - -let add = fn(x, y) { - x + y -}; - -let result = add(five, ten); -!-/*5; -10 > 5; - -if (5 < 10) { - return true; -} else { - return false; -} - -10 == 10; -10 != 9; -` - - tests := []struct { - expectedType token.TokenType - expectedLiteral string - }{ - {token.LET, "let"}, - {token.IDENT, "five"}, - {token.ASSIGN, "="}, - {token.INT, "5"}, - {token.SEMICOLON, ";"}, - - {token.LET, "let"}, - {token.IDENT, "ten"}, - {token.ASSIGN, "="}, - {token.INT, "10"}, - {token.SEMICOLON, ";"}, - - {token.LET, "let"}, - {token.IDENT, "add"}, - {token.ASSIGN, "="}, - {token.FUNCTION, "fn"}, - {token.LPAREN, "("}, - {token.IDENT, "x"}, - {token.COMMA, ","}, - {token.IDENT, "y"}, - {token.RPAREN, ")"}, - {token.LBRACE, "{"}, - {token.IDENT, "x"}, - {token.PLUS, "+"}, - {token.IDENT, "y"}, - {token.RBRACE, "}"}, - {token.SEMICOLON, ";"}, - - {token.LET, "let"}, - {token.IDENT, "result"}, - {token.ASSIGN, "="}, - {token.IDENT, "add"}, - {token.LPAREN, "("}, - {token.IDENT, "five"}, - {token.COMMA, ","}, - {token.IDENT, "ten"}, - {token.RPAREN, ")"}, - {token.SEMICOLON, ";"}, - - {token.BANG, "!"}, - {token.MINUS, "-"}, - {token.SLASH, "/"}, - {token.ASTERISK, "*"}, - {token.INT, "5"}, - {token.SEMICOLON, ";"}, - - {token.INT, "10"}, - {token.GT, ">"}, - {token.INT, "5"}, - {token.SEMICOLON, ";"}, - - {token.IF, "if"}, - {token.LPAREN, "("}, - {token.INT, "5"}, - {token.LT, "<"}, - {token.INT, "10"}, - {token.RPAREN, ")"}, - {token.LBRACE, "{"}, - {token.RETURN, "return"}, - {token.TRUE, "true"}, - {token.SEMICOLON, ";"}, - {token.RBRACE, "}"}, - {token.ELSE, "else"}, - {token.LBRACE, "{"}, - {token.RETURN, "return"}, - {token.FALSE, "false"}, - {token.SEMICOLON, ";"}, - {token.RBRACE, "}"}, - - {token.INT, "10"}, - {token.EQ, "=="}, - {token.INT, "10"}, - {token.SEMICOLON, ";"}, - - {token.INT, "10"}, - {token.NOT_EQ, "!="}, - {token.INT, "9"}, - {token.SEMICOLON, ";"}, - } - - l := New(input) - for i, tt := range tests { - tok := l.NextToken() - if tok.Type != tt.expectedType { - t.Fatalf("tests[%d] - tokentype wrong. expected=%q, got=%q", i, tt.expectedType, tok.Type) - } - - if tok.Literal != tt.expectedLiteral { - t.Fatalf("tests[%d] - tokenliteral wrong. expected=%q, got=%q", i, tt.expectedLiteral, tok.Literal) - } - } -} |