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[WIP] Fix minus literal #557

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[WIP] Fix minus literal #557

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a16004f
Remove the unused token.Incr and token.Decr
hachi8833 Dec 30, 2017
027f3bb
Add reduceSigns() and tests
hachi8833 Dec 31, 2017
477dfb1
Treat unary operator like '+1' or '-1'
hachi8833 Dec 31, 2017
a5f141b
Fix as CodeHound suggested
hachi8833 Dec 31, 2017
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105 changes: 89 additions & 16 deletions compiler/lexer/lexer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -42,8 +42,9 @@ func (l *Lexer) NextToken() token.Token {

var tok token.Token
l.resetNosymbol()

l.skipWhitespace()
l.reducePositiveSigns()

switch l.ch {
case '"', '\'':
tok.Literal = l.readString(l.ch)
Expand All @@ -63,13 +64,13 @@ func (l *Lexer) NextToken() token.Token {
tok = newToken(token.Assign, l.ch, l.line)
}
case '-':
if l.peekChar() == '-' {
tok.Literal = "--"
tok.Line = l.line
tok.Type = token.Decr
l.readChar()
l.readChar()
return tok
if isDigit(l.peekChar()) {
if l.isUnary() {
tok.Literal = string(l.readSignedNumber())
tok.Type = token.Int
tok.Line = l.line
return tok
}
} else if l.peekChar() == '=' {
tok.Literal = "-="
tok.Line = l.line
Expand Down Expand Up @@ -124,20 +125,20 @@ func (l *Lexer) NextToken() token.Token {
case ',':
tok = newToken(token.Comma, l.ch, l.line)
case '+':
if l.peekChar() == '+' {
tok.Literal = "++"
tok.Line = l.line
tok.Type = token.Incr
l.readChar()
l.readChar()
return tok
} else if l.peekChar() == '=' {
if l.peekChar() == '=' {
tok.Literal = "+="
tok.Line = l.line
tok.Type = token.PlusEq
l.readChar()
l.readChar()
return tok
} else if l.isUnary() {
if isDigit(l.peekChar()) {
tok.Literal = string(l.readSignedNumber())
tok.Type = token.Int
tok.Line = l.line
return tok
}
}
tok = newToken(token.Plus, l.ch, l.line)
case '{':
Expand Down Expand Up @@ -286,6 +287,15 @@ func (l *Lexer) readNumber() []rune {
return l.input[position:l.position]
}

func (l *Lexer) readSignedNumber() []rune {
position := l.position
l.readChar()
for isDigit(l.ch) {
l.readChar()
}
return l.input[position:l.position]
}

func (l *Lexer) readIdentifier() []rune {
position := l.position
for isLetter(l.ch) || isDigit(l.ch) {
Expand Down Expand Up @@ -389,6 +399,69 @@ func (l *Lexer) peekChar() rune {
// Peek shouldn't increment positions.
}

func (l *Lexer) reducePositiveSigns() {
if isPositiveSign(l.ch) {
if l.isUnary() {
if isPositiveSign(l.peekChar()) {
l.readChar()
for isPositiveSign(l.peekChar()) || isIdentifier(l.peekChar()) || isNegativeSign(l.peekChar()) {
l.readChar()
}
} else if isIdentifier(l.peekChar()) {
l.readChar()
}
}
}
}

func (l *Lexer) skipUnary() {
if l.ch == '+' && l.isUnary() {
l.readChar()
}
}

func (l *Lexer) isUnary() bool {
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I think this should be a helper function that receives an rune argument just like isIdentifier, instead of a lexer's function. We should change either its behavior or its name for the consistency.

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First I thought as that. But this helper function goes backward the lexer so *Lexer is needed.
Passing *Lexer via argument might be ineffective.
I will change the function name to checkUnary().

p := l.position
if p == 0 {
return true
}

p -= 1
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should replace p -= 1 with p--

switch l.input[p] {
case '(', ':', ',', '[', '{', '=', '>', '<', '*', '/', '%', '+', '-', 0:
return true
case ' ':
for l.input[p] == ' ' || p > 0 {
p--
switch l.input[p] {
case '(', ':', ',', '[', '{', '=', '>', '<', '*', '/', '%', '+', '-', 0:
return true
default:
return false
}
}
}
return false
}

func isIdentifier(ch rune) bool {
switch ch {
case '@', '(', ':', '[', '{':
//case '@', '(', ':', '[', '{', '-', 0:
return true
default:
return isLetter(ch) || isInstanceVariable(ch)
}
}

func isPositiveSign(ch rune) bool {
return ch == '+'
}

func isNegativeSign(ch rune) bool {
return ch == '-'
}

func isDigit(ch rune) bool {
return '0' <= ch && ch <= '9'
}
Expand Down
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