Remaining tidal features (#19)

* support repeat

* support "-" as rest

* parse "? " as "?0.5"

* separate expressions taking single value on the right, apply @ and ! at parse

* support polymeters without explicit count

* support range expressions with integers

* support slow expression

* support split expressions, aka "a b . c d" -> "[a b] [c d]"

* fix merging rests and holds

* refactor ing & cleanups

* update tidal differences explanation

src/tidal/cycle.pest

@@ -19,56 +19,61 @@ note    = ${ (^"a"|^"b"|^"c"|^"d"|^"e"|^"f"|^"g") }
 pitch   = ${ note ~ mark? ~ octave? ~ !(ASCII_ALPHANUMERIC)}
 
 /// type for empty steps
-rest = @{ "~" ~ !(ASCII_ALPHANUMERIC) }
+rest = @{ ("~" | "-") ~ !(ASCII_ALPHANUMERIC) }
 
 /// type for held steps
 hold = @{ "_" ~ !(ASCII_ALPHANUMERIC) }
 
 /// arbitrary string identifier type
 name = @{ (ASCII_ALPHANUMERIC | "_")+ }
 
+repeat = { "!" }
+
 /// possible literals for single steps
 single = { hold | rest | number | pitch | name }
 
-/// operators
-op_fast      = ${ "*" ~ parameter }
-op_target    = ${ ":" ~ parameter }
-op_degrade   = ${ "?" ~ parameter }
-op_replicate = ${ "!" ~ parameter }
-op_bjorklund = { "(" ~ (parameter ~ ",")+ ~ parameter ~ ")" }
-// op_weight    = ${ ("@") ~ parameter }
-// op_slow      = ${ "/" ~ parameter }
-// op_range     = { ".." ~ parameter } // ???
-op = _{ op_fast | op_target | op_degrade | op_replicate | op_bjorklund }
-
 /// groups
-subdivision     = { "[" ~ (stack | choices | section)? ~ "]" }
-alternating     = { "<" ~ (stack | section)? ~ ">" }
-polymeter       = { "{" ~ (stack | section)? ~ "}" ~ polymeter_tail }
-polymeter_tail  = { "%" ~  polymeter_count}
-polymeter_count = { (ASCII_NONZERO_DIGIT ~ ASCII_DIGIT* ~ !(ASCII_ALPHANUMERIC | "."))}
+subdivision     = { "[" ~ (stack | split | choices | section)? ~ "]" }
+alternating     = { "<" ~ (stack | split | section)? ~ ">" }
+
+polymeter_tail  = { "%" ~  single }
+polymeter       = { "{" ~ (stack | split | section)? ~ "}" ~ polymeter_tail? }
 
 group     = _{ subdivision | alternating | polymeter }
 
 // this should actually be { expr | group | single } at some point
 /// parameter for expressions with operators
 parameter = _{ single }
 
-expr      = { (single | group) ~ op+ }
+// target       = { (ASCII_ALPHANUMERIC | "_")+ }
+
+/// operators
+op_replicate = ${ "!" ~ single }
+op_weight    = ${ "@" ~ single? }
+op_degrade   = ${ "?" ~ single? }
+op_target    = ${ ":" ~ single }
+
+op_fast      = ${ "*" ~ parameter }
+op_slow      = ${ "/" ~ parameter }
+op_bjorklund = { "(" ~ (parameter ~ ",")+ ~ parameter ~ ")" }
+op           = _{ op_target | op_degrade | op_replicate | op_weight | op_fast | op_slow | op_bjorklund }
+
+expression  = { (single | group) ~ op+ }
+range       = ${ integer ~ ".." ~ integer }
 
 /// helper container that splits steps into sections
-section   = { (expr | single | group)+ }
+section   = { ( expression | range | single | repeat | group)+ }
 
 /// a single choice inside a choice list
-choice    = { expr | single | group }
+choice    = {  expression | range | single | group }
 /// at least 2 choices, can only be inside subdivisions or the root
 choices   = { (choice) ~ ("|" ~ choice)+ }
 
 /// parallel sections of events found inside groups
-stack     = { (section) ~ ("," ~ section)+ }
+stack     = { (split | section) ~ ("," ~ (split | section))+ }
 
-// shorthand for subdivisions
-// split          = { (section) ~ ("." ~ section)+ }
+// TODO shorthand for nested subdivisions
+split          = { (section) ~ ("." ~ section)+ }
 
 /// the root of the cycle
-mini = { SOI ~ ( stack | choices | section) ~ EOI }
+mini = { SOI ~ ( stack | split | choices | section) ~ EOI }