From d760902dce9e938b5d1dc4556d52e51492bb6f9b Mon Sep 17 00:00:00 2001 From: Alejandro Mery Date: Mon, 28 Aug 2023 22:14:45 +0000 Subject: [PATCH 1/3] lexer: introduce StateFn and the basic state machine loop Signed-off-by: Alejandro Mery --- lexer/lexer.go | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) create mode 100644 lexer/lexer.go diff --git a/lexer/lexer.go b/lexer/lexer.go new file mode 100644 index 0000000..26885ba --- /dev/null +++ b/lexer/lexer.go @@ -0,0 +1,17 @@ +// Package lexer provides basic helpers to implement parsers +package lexer + +// StateFn is a State Function of the parser +type StateFn func() (StateFn, error) + +// Run runs a state machine until the state function either +// returns nil or an error +func Run(fn StateFn) error { + var err error + + for fn != nil && err == nil { + fn, err = fn() + } + + return err +} -- 2.17.1 From a4124fb3e12526f5f8e62a5c2dfe5c4326400f25 Mon Sep 17 00:00:00 2001 From: Alejandro Mery Date: Mon, 28 Aug 2023 22:35:30 +0000 Subject: [PATCH 2/3] lexer: introduce Accept()/AcceptAll() helpers Signed-off-by: Alejandro Mery --- lexer/lexer.go | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) diff --git a/lexer/lexer.go b/lexer/lexer.go index 26885ba..2ee64ef 100644 --- a/lexer/lexer.go +++ b/lexer/lexer.go @@ -1,6 +1,8 @@ // Package lexer provides basic helpers to implement parsers package lexer +import "io" + // StateFn is a State Function of the parser type StateFn func() (StateFn, error) @@ -15,3 +17,38 @@ func Run(fn StateFn) error { return err } + +// Accept consumes a rune from the source if it meets the condition. +// it returns true if the condition was met and false if it wasn't. +func Accept(src io.RuneScanner, cond func(r rune) bool) bool { + r, _, err := src.ReadRune() + switch { + case err != nil: + return false + case cond(r): + return true + default: + _ = src.UnreadRune() + return false + } +} + +// AcceptAll consumes runes from the source as long as they meet the +// condition. it returns true if the condition was met for at least one rune, +// and false if it wasn't. +func AcceptAll(src io.RuneScanner, cond func(r rune) bool) bool { + var accepted bool + + for { + r, _, err := src.ReadRune() + switch { + case err != nil: + return accepted + case cond(r): + accepted = true + default: + _ = src.UnreadRune() + return accepted + } + } +} -- 2.17.1 From 48b75ec3c3785fc5c9a2bcd275e36df1211f382e Mon Sep 17 00:00:00 2001 From: Alejandro Mery Date: Mon, 28 Aug 2023 22:56:11 +0000 Subject: [PATCH 3/3] lexer: introduce a Position (Line, Column) handler Signed-off-by: Alejandro Mery --- lexer/position.go | 68 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 68 insertions(+) create mode 100644 lexer/position.go diff --git a/lexer/position.go b/lexer/position.go new file mode 100644 index 0000000..28db23c --- /dev/null +++ b/lexer/position.go @@ -0,0 +1,68 @@ +package lexer + +import "fmt" + +// Position indicates a line and column pair on a file. +// Counting starts at 1. +type Position struct { + Line int + Column int +} + +// String generates a pretty "(Line, Column)"" representation of the Position +func (p Position) String() string { + if p.Line == 0 { + p.Reset() + } + + return fmt.Sprintf("(%v, %v)", p.Line, p.Column) +} + +// GoString generates a string representation of the Position for %#v usage +func (p Position) GoString() string { + if p.Line == 0 { + p.Reset() + } + + return fmt.Sprintf("lexer.Position{%v, %v}", p.Line, p.Column) +} + +// Reset places a position at (1,1) +func (p *Position) Reset() { + p.Line, p.Column = 1, 1 +} + +// Step moves the column one place +func (p *Position) Step() { + if p.Line == 0 { + p.Reset() + } + + p.Column++ +} + +// Next returns a new Position one rune forward +// on the line +func (p Position) Next() Position { + if p.Line == 0 { + p.Reset() + } + + return Position{ + Line: p.Line, + Column: p.Column + 1, + } +} + +// NextLine returns a new Position at the begining of the next +// line. +func (p Position) NextLine() Position { + if p.Line == 0 { + p.Reset() + } + + return Position{ + Line: p.Line + 1, + Column: 1, + } +} -- 2.17.1