🧹 all: Clean-up lexing, comments and sample (#121)

This PR contains various minor clean-ups:

- lexing: Make empty string lexing consistent and clearer in JS and go
- index.js: Group exported funcs, fix comments, remove debug prints
- improve "guess my number" sample

This merges the following commits:
* samples: Improve "Guess my Number" sample
* frontend: Clean up index.js
* lexing: Clean up empty string literal lexing

     frontend/courses/sample/tour/rand.evy |  9 +++------
     frontend/index.js                     | 22 +++++++++-------------
     frontend/module/yace-editor.js        | 14 +++++---------
     pkg/lexer/lexer.go                    | 10 +++-------
     4 files changed, 20 insertions(+), 35 deletions(-)

Pull-Request: #121

Author: juliaogris

frontend/courses/sample/tour/rand.evy

@@ -7,11 +7,7 @@ while true
     guess := readn
 
     while guess != n
-        if guess > 10
-            print guess "Guess lower (1-10)."
-        else if guess < 1
-            print guess " Guess higher (1-10)."
-        else if guess < n
+        if guess < n
             print guess "Guess higher."
         else
             print guess "Guess lower."
@@ -23,7 +19,8 @@ while true
 end
 
 // readn reads a number.
-// If you enter a string that is not number
+// If the input is not a number readn
+// prints an error and repeats prompt.
 func readn:num
     while true
         str := read

frontend/index.js

@@ -45,14 +45,15 @@ function newEvyGo() {
     jsError,
     evySource,
     setEvySource,
+    afterStop,
+    registerEventHandler,
+    // canvas
     move,
     line,
     width,
     circle,
     rect,
     color,
-    afterStop,
-    registerEventHandler,
   }
   const go = new Go() // see wasm_exec.js
   go.importObject.env = Object.assign(go.importObject.env, evyEnv)
@@ -318,10 +319,8 @@ async function handleHashChange() {
     opts = { unit: "welcome" }
   }
   if (opts.content) {
-    console.log("start content update")
     const decoded = await decode(opts.content)
     editor.update({ value: decoded, errorLines: {} })
-    console.log("finished content update")
     return
   }
   let crumbs = ["Evy"]
@@ -411,7 +410,7 @@ function transformY(y) {
   return scaleY(y + canvas.offset.y)
 }
 
-// move is exported to evy go/wasm
+// move is exported to evy go/wasm.
 function move(x, y) {
   movePhysical(transformX(x), transformY(y))
 }
@@ -421,7 +420,7 @@ function movePhysical(px, py) {
   canvas.y = py
 }
 
-// line is exported to evy go/wasm
+// line is exported to evy go/wasm.
 function line(x2, y2) {
   const { ctx, x, y } = canvas
   const px2 = transformX(x2)
@@ -433,19 +432,19 @@ function line(x2, y2) {
   movePhysical(px2, py2)
 }
 
-// color is exported to evy go/wasm
+// color is exported to evy go/wasm.
 function color(ptr, len) {
   const s = memToString(ptr, len)
   canvas.ctx.fillStyle = s
   canvas.ctx.strokeStyle = s
 }
 
-// width is exported to evy go/wasm
+// width is exported to evy go/wasm.
 function width(n) {
   canvas.ctx.lineWidth = scaleX(n)
 }
 
-// rect is exported to evy go/wasm
+// rect is exported to evy go/wasm.
 function rect(dx, dy) {
   const { ctx, x, y } = canvas
   const sDX = scaleX(dx)
@@ -454,7 +453,7 @@ function rect(dx, dy) {
   movePhysical(x + sDX, y + sDY)
 }
 
-// circle is exported to evy go/wasm
+// circle is exported to evy go/wasm.
 function circle(r) {
   const { x, y, ctx } = canvas
   ctx.beginPath()
@@ -682,7 +681,6 @@ function showConfetti() {
 // --- Share / load snippets -------------------------------------------
 
 async function share() {
-  console.log("share")
   await format()
   const el = document.querySelector("#modal-share")
 
@@ -694,7 +692,6 @@ async function share() {
     button.onclick = hideModal
     el.replaceChildren(msg, button)
     showSharing()
-    console.log("Fix errors first please.")
     return
   }
   const encoded = await encode(editor.value)
@@ -714,7 +711,6 @@ async function share() {
   }
   el.replaceChildren(msg, input, button)
   showSharing()
-  console.log(encoded)
 }
 
 async function encode(input) {

frontend/module/yace-editor.js

@@ -627,20 +627,16 @@ function readIdent(s, i) {
 }
 
 function readString(s, i) {
-  let backslashCnt = 0
+  let escaped = false
   while (i < s.length) {
     const c = s[i]
-    if (c === "\\") {
-      backslashCnt++
-    } else {
-      backslashCnt = 0
-    }
-    if (c === '"' && backslashCnt % 2 == 0) {
-      return i + 1
-    }
     if (c === "\n") {
       return i
     }
+    if (c === '"' && !escaped) {
+      return i + 1
+    }
+    escaped = c === "\\" && !escaped
     i++
   }
   return i

pkg/lexer/lexer.go

@@ -191,15 +191,11 @@ func (l *Lexer) readIdent() string {
 
 func (l *Lexer) readString() (string, error) {
 	pos := l.pos
-	backslashCnt := 0
+	escaped := false
 	for {
-		if l.cur == '\\' {
-			backslashCnt++
-		} else {
-			backslashCnt = 0
-		}
+		escaped = l.cur == '\\' && !escaped
 		pr := l.peekRune()
-		if pr == '"' && backslashCnt%2 == 0 {
+		if pr == '"' && !escaped {
 			l.advance() // end of string
 			break
 		}