TopDownOperatorPrecedenceにおけるExpressionの解析処理を追う

by kooooohe

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TopDownOperatorPreceden ce(再帰下降構文解析)におけるExpression(式)の解析処理を追う

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3 + 2 + 1

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((3 + 2) + 1)

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*ast.InfixExpression *ast.InfixExpression *ast.IntegerLiteral *ast.IntegerLiteral *ast.IntegerLiteral 3 2 1

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BEGIN parseExpresssionStatement BEGIN parseExpresssion BEGIN parseIntegerLiteral END parseIntegerLiteral BEGIN parseInfixExpression BEGIN parseExpresssion BEGIN parseIntegerLiteral END parseIntegerLiteral END parseExpresssion END parseInfixExpression BEGIN parseInfixExpression BEGIN parseExpresssion BEGIN parseIntegerLiteral END parseIntegerLiteral END parseExpresssion END parseInfixExpression END parseExpresssion END parseExpresssionStatement

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-3 + 10 * 2 + 1; 18

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(((-3) + (10 * 2)) + 1);

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1

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BEGIN parseExpresssionStatement BEGIN parseExpresssion BEGIN parsePrefixExpression BEGIN parseExpresssion BEGIN parseIntegerLiteral END parseIntegerLiteral END parseExpresssion END parsePrefixExpression BEGIN parseInfixExpression BEGIN parseExpresssion BEGIN parseIntegerLiteral END parseIntegerLiteral BEGIN parseInfixExpression BEGIN parseExpresssion BEGIN parseIntegerLiteral END parseIntegerLiteral END parseExpresssion END parseInfixExpression END parseExpresssion END parseInfixExpression BEGIN parseInfixExpression BEGIN parseExpresssion BEGIN parseIntegerLiteral END parseIntegerLiteral END parseExpresssion END parseInfixExpression END parseExpresssion END parseExpresssionStatement

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func (p *Parser) parseExpressionStatement() *ast.ExpressionStatement { stmt := &ast.ExpressionStatement{Token: p.curToken} stmt.Expression = p.parseExpression(LOWEST) if p.peekTokenIs(token.SEMICOLON) { p.nextToken() } return stmt }

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func (p *Parser) parseExpression(precedence int /*LOWEST*/) ast.Expression { prefix/*parsePrefixExpression*/ := p.prefixParseFns[p.curToken.Type] /* - MINUS*/ if prefix == nil { p.noPrefixParseFnError(p.curToken.Type) return nil } leftExp := prefix()/*parsePrefixExpression*/ for !p.peekTokenIs(token.SEMICOLON) && precedence < p.peekPrecedence() { infix := p.infixParseFns[p.peekToken.Type] if infix == nil { return leftExp } p.nextToken() leftExp = infix(leftExp) } return leftExp } 1

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func (p *Parser) parsePrefixExpression() ast.Expression { expression := &ast.PrefixExpression{ Token: p.curToken, /* - MINUS*/ Operator: p.curToken.Literal, } p.nextToken() /* 3*/ expression.Right = p.parseExpression(PREFIX) return expression }

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 -

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func (p *Parser) parseExpression(precedence int /*PREFIX*/) ast.Expression { prefix/*parsePrefixExpression*/ := p.prefixParseFns[p.curToken.Type] /* 3 IDENT*/ if prefix == nil { p.noPrefixParseFnError(p.curToken.Type) return nil } leftExp := prefix()/*parseIntegerLiteral*/ for !p.peekTokenIs(token.SEMICOLON) && precedence < p.peekPrecedence() { infix := p.infixParseFns[p.peekToken.Type] if infix == nil { return leftExp } p.nextToken() leftExp = infix(leftExp) } return leftExp } 2

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func (p *Parser) parseIntegerLiteral() ast.Expression { lit := &ast.IntegerLiteral{Token: p.curToken} value, err := strconv.ParseInt(p.curToken.Literal, 0, 64) if err != nil { msg := fmt.Sprintf("could not parse %q as integer", p.curToken.Literal) p.errors = append(p.errors, msg) return nil } lit.Value = value return lit }

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 -

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func (p *Parser) parseExpression(precedence int /*PREFIX*/) ast.Expression { prefix/*parsePrefixExpression*/ := p.prefixParseFns[p.curToken.Type] /* 3 IDENT*/ if prefix == nil { p.noPrefixParseFnError(p.curToken.Type) return nil } leftExp/*&ast.IntegerLiteral{Token: p.curToken} 3 */ := prefix()/*parseIntegerLiteral*/ /*FLASE*/ for !p.peekTokenIs(token.SEMICOLON) && precedence/*PREFIX*/ < p.peekPrecedence() /* PLUS + */ { infix := p.infixParseFns[p.peekToken.Type] if infix == nil { return leftExp } p.nextToken() leftExp = infix(leftExp) } return leftExp } 2

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func (p *Parser) parseExpression(precedence int /*LOWEST*/) ast.Expression { prefix/*parsePrefixExpression*/ := p.prefixParseFns[p.curToken.Type] /* - MINUS*/ if prefix == nil { p.noPrefixParseFnError(p.curToken.Type) return nil } leftExp := prefix()/*parsePrefixExpression*/ leftExp / * &ast.PrefixExpression{Token: /* - MINUS*/ Operator: /* - */,Rignt: &ast.IntegerLiteral{Token:3} } */ /*TRUE*/ for !p.peekTokenIs(token.SEMICOLON) && precedence/*LOWEST*/ < p.peekPrecedence() /*PLUS*/{ infix := p.infixParseFns[p.peekToken.Type]/*PLUS*/ if infix == nil { return leftExp } p.nextToken() leftExp = infix(leftExp) /*parseInfixExpression*/ } return leftExp } 1

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/* left = &ast.PrefixExpression{Token: /* - MINUS*/ Operator: /* - */,Rignt: &ast.IntegerLiteral{Token:3} } */ func (p *Parser) parseInfixExpression(left ast.Expression) ast.Expression { expression := &ast.InfixExpression{ Token: p.curToken, Operator: p.curToken.Literal, Left: left, } precedence := p.curPrecedence() / * PLUS*/ p.nextToken() expression.Right = p.parseExpression(precedence) return expression }

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func (p *Parser) parseExpression(precedence int / * PLUS*/ ) ast.Expression { prefix := p.prefixParseFns[p.curToken.Type / * 10*/ ] if prefix == nil { p.noPrefixParseFnError(p.curToken.Type) return nil } leftExp := prefix() /*parseIntegerLiteral*/ for !p.peekTokenIs(token.SEMICOLON) && precedence < p.peekPrecedence() { infix := p.infixParseFns[p.peekToken.Type] if infix == nil { return leftExp } p.nextToken() leftExp = infix(leftExp) } return leftExp } 3

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func (p *Parser) parseIntegerLiteral() ast.Expression { lit := &ast.IntegerLiteral{Token: p.curToken} /*10*/ value, err := strconv.ParseInt(p.curToken.Literal, 0, 64) if err != nil { msg := fmt.Sprintf("could not parse %q as integer", p.curToken.Literal) p.errors = append(p.errors, msg) return nil } lit.Value = value return lit }

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 -

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func (p *Parser) parseExpression(precedence int / * PLUS*/ ) ast.Expression { prefix := p.prefixParseFns[p.curToken.Type / * 10*/ ] if prefix == nil { p.noPrefixParseFnError(p.curToken.Type) return nil } leftExp/*&ast.IntegerLiteral{Token: 10} */ := prefix() /*parseIntegerLiteral*/ /*TRUE*/ for !p.peekTokenIs(token.SEMICOLON) && precedence/*PLUS*/ < p.peekPrecedence()/*PRODUCT*/ { infix := p.infixParseFns[p.peekToken.Type] if infix == nil { return leftExp } p.nextToken() leftExp = infix(leftExp) /*parseInfixExpression*/ } return leftExp } 3

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func (p *Parser) parseInfixExpression(left ast.Expression /*&ast.IntegerLiteral{Token: 10} */ ) ast.Expression { expression := &ast.InfixExpression{ Token: p.curToken, Operator: p.curToken.Literal, Left: left,/*&ast.IntegerLiteral{Token: 10} */ } precedence := p.curPrecedence() /*PRODUCT */ p.nextToken() expression.Right = p.parseExpression(precedence) return expression }

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 -

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func (p *Parser) parseExpression(precedence int /*PRODUCT*/ ) ast.Expression { prefix := p.prefixParseFns[p.curToken.Type/*2*/ ] if prefix == nil { p.noPrefixParseFnError(p.curToken.Type) return nil } leftExp := prefix()/* parseIntegerLiteral*/ for !p.peekTokenIs(token.SEMICOLON) && precedence < p.peekPrecedence() { infix := p.infixParseFns[p.peekToken.Type] if infix == nil { return leftExp } p.nextToken() leftExp = infix(leftExp) } return leftExp } 4

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func (p *Parser) parseIntegerLiteral() ast.Expression { lit := &ast.IntegerLiteral{Token: p.curToken} /*2*/ value, err := strconv.ParseInt(p.curToken.Literal, 0, 64) if err != nil { msg := fmt.Sprintf("could not parse %q as integer", p.curToken.Literal) p.errors = append(p.errors, msg) return nil } lit.Value = value return lit }

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 - *

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func (p *Parser) parseExpression(precedence int /*PRODUCT*/ ) ast.Expression { prefix := p.prefixParseFns[p.curToken.Type/*2*/ ] if prefix == nil { p.noPrefixParseFnError(p.curToken.Type) return nil } leftExp/* &ast.IntegerLiteral{Token: 2}*/ := prefix()/* parseIntegerLiteral*/ /*FALSE*/ for !p.peekTokenIs(token.SEMICOLON) && precedence/*PRODUCT*/ < p.peekPrecedence() /*PLUS*/ { infix := p.infixParseFns[p.peekToken.Type] if infix == nil { return leftExp } p.nextToken() leftExp = infix(leftExp) } return leftExp } 4

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func (p *Parser) parseInfixExpression(left ast.Expression /*&ast.IntegerLiteral{Token: 10} */ ) ast.Expression { expression := &ast.InfixExpression{ Token: p.curToken,*PLUS*/ Operator: p.curToken.Literal/*-*/ , Left: left,/*&ast.IntegerLiteral{Token: 10} */ } precedence := p.curPrecedence() /*PRODUCT */ p.nextToken() expression.Right/* &ast.IntegerLiteral{Token: 2}*/ = p.parseExpression(precedence) return expression }

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func (p *Parser) parseExpression(precedence int / * PLUS*/ ) ast.Expression { prefix := p.prefixParseFns[p.curToken.Type / * 10*/ ] if prefix == nil { p.noPrefixParseFnError(p.curToken.Type) return nil } leftExp/*&ast.IntegerLiteral{Token: 10} */ := prefix() /*parseIntegerLiteral*/ /*TRUE*/ for !p.peekTokenIs(token.SEMICOLON) && precedence/*PLUS*/ < p.peekPrecedence()/*PRODUCT*/ { infix := p.infixParseFns[p.peekToken.Type] if infix == nil { return leftExp } p.nextToken() leftExp = infix(leftExp) /*parseInfixExpression*/ &ast.InfixExpression{Token: PLUS,Operator: +l ,Left:/*&ast.IntegerLiteral{Token: 10} */ , Right: /*&ast.IntegerLiteral{Token: 2} */ } } 3

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/* left = &ast.PrefixExpression{Token: /* - MINUS*/ Operator: /* - */,Rignt: &ast.IntegerLiteral{Token:3} } */ func (p *Parser) parseInfixExpression(left ast.Expression) ast.Expression { expression := &ast.InfixExpression{ Token: p.curToken, PLUS Operator: p.curToken.Literal, PLUS Left: left, } precedence := p.curPrecedence() / * PLUS*/ p.nextToken() expression.Right = p.parseExpression(precedence) Right &ast.InfixExpression{Token: PLUS,Operator: +l ,Left:/*&ast.IntegerLiteral{Token: 10} */ , Right: /*&ast.IntegerLiteral{Token: 2} */ }} return expression

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&ast.InfixExpression{ Token: PLUS Operator: PLUS Left: &ast.PrefixExpression{Token: /* - MINUS*/ Operator: /* - */,Rignt: &ast.IntegerLiteral{Token:3} } , Right: &ast.InfixExpression{Token: PLUS,Operator: +l ,Left:/*&ast.IntegerLiteral{Token: 10} */ , Right: /*&ast.IntegerLiteral{Token: 2} */ }} } = X

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 - + *

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func (p *Parser) parseExpression(precedence int /*LOWEST*/) ast.Expression { prefix/*parsePrefixExpression*/ := p.prefixParseFns[p.curToken.Type] /* - MINUS*/ if prefix == nil { p.noPrefixParseFnError(p.curToken.Type) return nil } leftExp := prefix()/*parsePrefixExpression*/ /*TRUE*/ for !p.peekTokenIs(token.SEMICOLON) && precedence/*LOWEST*/ < p.peekPrecedence()/* PLUS*/ { infix := p.infixParseFns[p.peekToken.Type]/* PLUS*/ if infix == nil { return leftExp } p.nextToken() leftExp = infix(leftExpX)/*parseInfixExpression*/ } return leftExp } 1

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func (p *Parser) parseInfixExpression(left ast.Expression X) ast.Expression { expression := &ast.InfixExpression{ Token: p.curToken, PLUS Operator: p.curToken.Literal,PLUS Left: left, X } precedence := p.curPrecedence() PLUS p.nextToken() expression.Right = p.parseExpression(precedence) return expression }

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func (p *Parser) parseExpression(precedence int PLUS) ast.Expression { prefix := p.prefixParseFns[p.curToken.Type] 1 if prefix == nil { p.noPrefixParseFnError(p.curToken.Type) return nil } leftExp := prefix() for !p.peekTokenIs(token.SEMICOLON) && precedence < p.peekPrecedence() { infix := p.infixParseFns[p.peekToken.Type] if infix == nil { return leftExp } p.nextToken() leftExp = infix(leftExp) } return leftExp } 5

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func (p *Parser) parseIntegerLiteral() ast.Expression { lit := &ast.IntegerLiteral{Token: p.curToken} 1 value, err := strconv.ParseInt(p.curToken.Literal, 0, 64) if err != nil { msg := fmt.Sprintf("could not parse %q as integer", p.curToken.Literal) p.errors = append(p.errors, msg) return nil } lit.Value = value return lit }

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 - * +

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 - + * +

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func (p *Parser) parseExpression(precedence int /*LOWEST*/) ast.Expression { prefix/*parsePrefixExpression*/ := p.prefixParseFns[p.curToken.Type] /* - MINUS*/ if prefix == nil { p.noPrefixParseFnError(p.curToken.Type) return nil } leftExp := prefix()/*parsePrefixExpression*/ /*TRUE*/ for !p.peekTokenIs(token.SEMICOLON) && precedence/*LOWEST*/ < p.peekPrecedence()/* PLUS*/ { infix := p.infixParseFns[p.peekToken.Type]/* PLUS*/ if infix == nil { return leftExp } p.nextToken() leftExp = infix(leftExpX)/*parseInfixExpression*/ } return leftExp } 1

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&ast.InfixExpression { Token: PLUS Operator: PLUS Left: left, X Right: 1 }

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 -

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 -

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 -

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 -

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 - *

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 - + *

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 - + * +

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*ast.InfixExpres sion *ast.InfixExpres sion *ast.PrefixExpre ssion *ast.InfixExpres sion *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al *ast.IntegerLiter al 3 10 2 1 - * +