gistfile1.r

rexp.to.sexp <- function(exp){
     exp <- substitute(exp)
     if(is.call(exp)) {
          s <- "("
          i <- 0
          while (i < length(exp)) {
               i <- i + 1
               separator <- if( i == 1 ) "" else " "
               s <- paste(s,
                          eval(substitute(rexp.to.sexp(e), list(e = exp[[i]]))),
                          sep = separator)
          }
          paste(s, ")", sep = "")
     } else if (is.list(exp)) {
          eval(substitute(rexp.to.sexp(e), list(e = as.call(Map(as.name, names(exp))))))
     } else if (is.character(exp)) {
          paste("\"", as.character(exp), "\"", sep="")
     } else {
          as.character(exp)
     }
}

rexp.to.scheme.exp <- function(exp){
     exp <- substitute(exp)
     if (is.call(exp)) {
          if (exp[[1]] == quote(`function`)) {
               exp <- exp[-length(exp)]
          }
          s <- "("
          i <- 0
          while (i < length(exp)) {
               i <- i + 1
               separator <- if( i == 1 ) "" else " "
               s <- paste(s,
                          eval(substitute(rexp.to.scheme.exp(e), list(e = exp[[i]]))),
                          sep = separator)
          }
          paste(s, ")", sep = "")
     } else if (is.list(exp)) {
          eval(substitute(rexp.to.sexp(e), list(e = as.call(Map(as.name, names(exp))))))
     } else if (is.character(exp)) {
          paste("\"", as.character(exp), "\"", sep="")
     } else if(exp == quote(`<-`)) {
          "define"
     } else if (exp == quote(`{`)) {
          "begin"
     } else if (exp == quote(`(`)) {
          "begin"
     } else if (exp == quote(`function`)) {
          "lambda"
     } else if (exp == quote(`[`)) {
          "aref"
     } else {
          as.character(exp)
     }
}