allow integer range as when choice value

compiler/src/prog8/compiler/astprocessing/CodeDesugarer.kt

@@ -319,4 +319,35 @@ _after:
         }
         return noModifications
     }
+
+    override fun after(whenChoice: WhenChoice, parent: Node): Iterable<IAstModification> {
+        // replace a range expression in a when by the actual list of numbers it represents
+        val values = whenChoice.values
+        if(values!=null && values.size==1) {
+            val conditionType = (whenChoice.parent as When).condition.inferType(program)
+            val intRange = (values[0] as? RangeExpression)?.toConstantIntegerRange()
+            if(conditionType.isKnown && intRange != null) {
+                if(intRange.count()>255)
+                    errors.err("values list too long", values[0].position)
+                else {
+                    val dt = conditionType.getOrUndef().base
+                    val newValues = intRange.map {
+                        val num = NumericLiteral(BaseDataType.LONG, it.toDouble(), values[0].position)
+                        num.linkParents(whenChoice)
+                        val cast = num.cast(dt, true)
+                        if (cast.isValid) cast.valueOrZero() else null
+                    }
+                    if(null !in newValues) {
+                        if(newValues.size>=10)
+                            errors.warn("long list of values, checking will not be very efficient", values[0].position)
+                        values.clear()
+                        for(num in newValues)
+                            values.add(num!!)
+                    }
+                }
+            }
+        }
+
+        return noModifications
+    }
 }

compiler/test/ast/TestVariousCompilerAst.kt

@@ -4,6 +4,7 @@ import io.kotest.assertions.throwables.shouldThrow
 import io.kotest.core.spec.style.FunSpec
 import io.kotest.engine.spec.tempdir
 import io.kotest.matchers.comparables.shouldBeGreaterThan
+import io.kotest.matchers.nulls.shouldNotBeNull
 import io.kotest.matchers.shouldBe
 import io.kotest.matchers.shouldNotBe
 import io.kotest.matchers.string.shouldContain
@@ -684,6 +685,40 @@ main
         errors.errors[0] shouldContain "use if"
     }
 
+    test("when on range expressions is ok") {
+        val src="""
+
+main {
+
+    sub start()  {
+        when cx16.r0L {
+            21 to 29 step 2 -> cx16.r1L++
+            else -> cx16.r1L--
+        }
+    }
+}"""
+        compileText(VMTarget(), optimize=false, src, outputDir, writeAssembly=false).shouldNotBeNull()
+    }
+
+    test("when on range expressions outside value datatype is error") {
+        val src="""
+
+main {
+
+    sub start()  {
+        when cx16.r0L {
+            300 to 400 -> cx16.r1L++
+            else -> cx16.r1L--
+        }
+    }
+}"""
+        val errors = ErrorReporterForTests()
+        compileText(VMTarget(), optimize=false, src, outputDir, writeAssembly=false, errors = errors) shouldBe null
+        errors.errors.size shouldBe 1
+        errors.errors[0] shouldContain "values must be constant numbers"
+    }
+
+
     test("sizeof number const evaluation in vardecl") {
         val src="""
 main {

docs/source/programming.rst

@@ -751,19 +751,24 @@ action. It is possible to combine several choices to result in the same action::
     when value {
         4 -> txt.print("four")
         5 -> txt.print("five")
-        10,20,30 -> {
-            txt.print("ten or twenty or thirty")
-        }
+        10,20,30 -> txt.print("ten or twenty or thirty")
+        50 to 60 step 2 -> txt.print("fifty to sixty, even")
         else -> txt.print("don't know")
     }
 
 The when-*value* can be any expression but the choice values have to evaluate to
 compile-time constant integers (bytes or words). They also have to be the same
 datatype as the when-value, otherwise no efficient comparison can be done.
-The else part is optional.
+You can explicitly put a list of numbers that all should result in the same case,
+or even use any *range expression* as long as it denotes a constant list of numbers.
+Be aware that every number is compared individually so using long lists of numbers and/or
+many choice cases will result in poor performance.
+
 Choices can result in a single statement or a block of multiple statements in which
 case you have to use { } to enclose them.
 
+The else part is optional.
+
 
 .. note::
     Instead of chaining several value equality checks together using ``or`` (ex.: ``if x==1 or xx==5 or xx==9``),

docs/source/todo.rst

@@ -9,7 +9,6 @@ TODO
 Future Things and Ideas
 ^^^^^^^^^^^^^^^^^^^^^^^
 
-- allow integer range as when choice? because 1,2,3,4,5 is already allowed, so perhaps 1 to 5 should be allowed too? However, [1,2,3,4,5] usually is the desugared equivalent of 1 to 5 and choice values can't be arrays. Unless we allow array literals as well and desugar those into separate labels too.
 - Kotlin: can we use inline value classes in certain spots?
 - add float support to the configurable compiler targets
 - Improve the SublimeText syntax file for prog8, you can also install this for 'bat': https://github.com/sharkdp/bat?tab=readme-ov-file#adding-new-syntaxes--language-definitions

examples/test.p8

@@ -1,31 +1,17 @@
-%import psg
+%import textio
 %zeropage basicsafe
 %option no_sysinit
 
 main {
 
     sub start()  {
-        psg.init()
+        cx16.r0L = 25
 
-        psg.voice(5, psg.LEFT, 0, psg.TRIANGLE, 0)
-        psg.freq(5, 1600)
-        psg.envelope(5, 63, 10, 50, 2)
-
-        psg.voice(6, psg.RIGHT, 0, psg.SAWTOOTH, 0)
-        psg.freq(6, 1200)
-        psg.envelope(6, 63, 2, 50, 10)
-
-        repeat 140 {
-            sys.waitvsync()
-            psg.envelopes_irq()
-        }
-
-        psg.voice(5, psg.DISABLED, 0, 0, 0)
-        psg.voice(6, psg.DISABLED, 0, 0, 0)
-        psg.silent()
-        repeat {
-            sys.waitvsync()
-            psg.envelopes_irq()
+        when cx16.r0L {
+            0 -> txt.print("zero")
+            1 -> txt.print("one")
+            21 to 29 step 2 -> txt.print("between 20 and 30 and odd")
+            else -> txt.print("something else")
         }
     }
 }