diff --git a/R/parse_pcs.R b/R/parse_pcs.R
new file mode 100644
index 00000000..3668d4bd
--- /dev/null
+++ b/R/parse_pcs.R
@@ -0,0 +1,140 @@
+library(paradox)
+
+load_all()
+
+TOKENS = c('NAME', 'NUM', 'BOOL', 'NEWLINE')
+LITERALS = c('{','}','[',']', ',')
+
+Lexer <- R6::R6Class("Lexer",
+  public = list(
+    tokens = TOKENS,
+    literals = LITERALS,
+    t_NAME = '[a-zA-Z_][a-zA-Z0-9_]*',
+    t_NEWLINE = function(re = '\\n+', t) {
+      t$lexer$lineno <- t$lexer$lineno + nchar(t$value)
+      t$value = NULL
+      return(t)
+    },
+    t_NUM = function(re = "[0-9]*\\.?[0-9]+((E|e)(\\+|-)?[0-9]+)?", t) {
+      t$value = as.numeric(t$value)
+      return(t)
+    },
+    t_BOOL = function(re='(T|F)', t) {
+      t$value = as.logical(t$value)
+      return(t)
+    },
+    t_ignore = " \t",
+    # t_newline = function(re='\\n+', t) {
+      # t$lexer$lineno <- t$lexer$lineno + nchar(t$value)
+      # return(NULL)
+    # },
+    t_error = function(t) {
+      stopf("Illegal character in PCS format: '%s'", t$value[1])
+    }
+  )
+)
+
+# FIXME: error handling and error messages for invalid sequences seem to be really bad
+# FIXME: remove ::: for NO_DEF
+# FIXME: add simple dependencies
+# FIXME: better errmsg, show current line where lexer is
+
+Parser <- R6::R6Class("Parser",
+  public = list(
+    tokens = TOKENS,
+    literals = LITERALS,
+    names = new.env(hash=TRUE),
+    p_paramset = function(doc = "paramset : paramlist", p) {
+      p$set(1, ParamSet$new(p$get(2)))
+    },
+
+    p_paramlist = function(doc = "paramlist : param
+                                            | param NEWLINE paramlist", p) {
+      if (p$length() == 2L)
+        xs = list(p$get(2))
+      else if (p$length() == 4L)
+        xs = c(list(p$get(2)), p$get(4))
+      p$set(1, xs)
+    },
+
+    p_param = function(doc = "param : paramint
+                                    | paramdbl
+                                    | paramfct
+                                    | paramlgl" , p) {
+      p$set(1, p$get(2))
+    },
+
+    p_paramint = function(doc = "paramint : NAME '[' NUM ',' NUM ']' '[' NUM ']' NAME
+                                          | NAME '[' NUM ',' NUM ']' '!'" , p) {
+      isym = p$get(11)
+      if (isym != "i")
+          stopf("Final symbol after a numerical param can only be 'i' for an 'int', not: %s", isym)
+      def = if (p$length() == 11L) p$get(9) else paradox:::NO_DEF
+      param = ParamInt$new(id = p$get(2), lower = p$get(4), upper = p$get(6), default = def)
+      p$set(1, param)
+    },
+
+    p_paramdbl = function(doc = "paramdbl : NAME '[' NUM ',' NUM ']' '[' NUM ']'
+                                          | NAME '[' NUM ',' NUM ']'" , p) {
+      def = if (p$length() == 10L) p$get(9) else paradox:::NO_DEF
+      param = ParamDbl$new(id = p$get(2), lower = p$get(4), upper = p$get(6), default = def)
+      p$set(1, param)
+    },
+
+    p_paramlgl = function(doc = "paramlgl : NAME '[' BOOL ']'
+                                          | NAME" , p) {
+      def = if (p$length() == 5L) p$get(4) else paradox:::NO_DEF
+      param = ParamLgl$new(id = p$get(2),  default = def)
+      p$set(1, param)
+    },
+
+    p_paramfct = function(doc = "paramfct : NAME '{' fct_vallist '}' '[' NAME ']'
+                                          | NAME '{' fct_vallist '}'" , p) {
+      def = if (p$length() == 8L) p$get(7) else paradox:::NO_DEF
+      param = ParamFct$new(id = p$get(2), values = p$get(4), default = def)
+      p$set(1, param)
+    },
+
+    p_fct_vallist = function(doc = "fct_vallist : NAME
+                                                | NAME ',' fct_vallist" , p) {
+      if (p$length() == 2L)
+        xs = p$get(2)
+      else if (p$length() == 4L)
+        xs = c(p$get(2), p$get(4))
+      p$set(1, xs)
+    },
+
+    p_error = function(p) {
+      # ppp <<- p
+      # n = p$lexer$lineno
+      # s = p$lexer$lexdata
+      # str_split()
+      # print(n)
+      if (is.null(p))
+        stop("Syntax error parings PCS format at EOF")
+      else
+        stopf("Syntax error parsing PCS format at '%s'", p$value)
+    }
+  )
+)
+
+
+
+
+
+
+lexer  = rly::lex(Lexer)
+parser = rly::yacc(Parser)
+
+s = " foo {1, 7] [3] i
+      bar [1, 3.4] [2.2]
+      b "
+x = parser$parse(s, lexer)
+print(x)
+
+
+
+
+
+
+