1 files changed, 135 insertions, 0 deletions
diff --git a/r/step7_quote.r b/r/step7_quote.r
new file mode 100644
index 0000000..c6b6637
--- /dev/null
+++ b/r/step7_quote.r
@@ -0,0 +1,135 @@
+if(!exists("..readline..")) source("readline.r")
+if(!exists("..types..")) source("types.r")
+if(!exists("..reader..")) source("reader.r")
+if(!exists("..printer..")) source("printer.r")
+if(!exists("..env..")) source("env.r")
+if(!exists("..core..")) source("core.r")
+
+# read
+READ <- function(str) {
+    return(read_str(str))
+}
+
+# eval
+is_pair <- function(x) {
+    .sequential_q(x) && length(x) > 0
+}
+
+quasiquote <- function(ast) {
+    if (!is_pair(ast)) {
+        new.list(new.symbol("quote"),
+                 ast)
+    } else if (.symbol_q(ast[[1]]) && ast[[1]] == "unquote") {
+        ast[[2]]
+    } else if (is_pair(ast[[1]]) &&
+               .symbol_q(ast[[1]][[1]]) &&
+               ast[[1]][[1]] == "splice-unquote") {
+        new.list(new.symbol("concat"),
+                 ast[[1]][[2]],
+                 quasiquote(slice(ast, 2)))
+    } else {
+        new.list(new.symbol("cons"),
+                 quasiquote(ast[[1]]),
+                 quasiquote(slice(ast, 2)))
+    }
+}
+
+eval_ast <- function(ast, env) {
+    if (.symbol_q(ast)) {
+        Env.get(env, ast)
+    } else if (.list_q(ast)) {
+        new.listl(lapply(ast, function(a) EVAL(a, env)))
+    } else if (.vector_q(ast)) {
+        new.vectorl(lapply(ast, function(a) EVAL(a, env)))
+    } else {
+        ast
+    }
+}
+
+EVAL <- function(ast, env) {
+    repeat {
+
+    #cat("EVAL: ", .pr_str(ast,TRUE), "\n", sep="")
+    if (!.list_q(ast)) {
+        return(eval_ast(ast, env))
+    }
+
+    # apply list
+    switch(paste("l",length(ast),sep=""),
+           l0={ return(ast) },
+           l1={ a0 <- ast[[1]]; a1 <- NULL;     a2 <- NULL },
+           l2={ a0 <- ast[[1]]; a1 <- ast[[2]]; a2 <- NULL },
+              { a0 <- ast[[1]]; a1 <- ast[[2]]; a2 <- ast[[3]] })
+    if (length(a0) > 1) a0sym <- "__<*fn*>__"
+    else                a0sym <- as.character(a0)
+    if (a0sym == "def!") {
+        res <- EVAL(a2, env)
+        return(Env.set(env, a1, res))
+    } else if (a0sym == "let*") {
+        let_env <- new.Env(env)
+        for(i in seq(1,length(a1),2)) {
+            Env.set(let_env, a1[[i]], EVAL(a1[[i+1]], let_env))
+        }
+        ast <- a2
+        env <- let_env
+    } else if (a0sym == "quote") {
+        return(a1)
+    } else if (a0sym == "quasiquote") {
+        ast <- quasiquote(a1)
+    } else if (a0sym == "do") {
+        eval_ast(slice(ast,2,length(ast)-1), env)
+        ast <- ast[[length(ast)]]
+    } else if (a0sym == "if") {
+        cond <- EVAL(a1, env)
+        if (.nil_q(cond) || identical(cond, FALSE)) {
+            if (length(ast) < 4) return(NULL)
+            ast <- ast[[4]]
+        } else {
+            ast <- a2
+        }
+    } else if (a0sym == "fn*") {
+        return(malfunc(a2, env, a1))
+    } else {
+        el <- eval_ast(ast, env)
+        f <- el[[1]]
+        if (class(f) == "MalFunc") {
+            ast <- f$ast
+            env <- f$gen_env(slice(el,2))
+        } else {
+            return(do.call(f,slice(el,2)))
+        }
+    }
+
+    }
+}
+
+# print
+PRINT <- function(exp) {
+    return(.pr_str(exp, TRUE))
+}
+
+# repl loop
+repl_env <- new.Env()
+rep <- function(str) return(PRINT(EVAL(READ(str), repl_env)))
+
+# core.r: defined using R
+for(k in names(core_ns)) { Env.set(repl_env, k, core_ns[[k]]) }
+Env.set(repl_env, "eval", function(ast) EVAL(ast, repl_env))
+Env.set(repl_env, "*ARGV*", function(ast) EVAL(ast, repl_env))
+
+# core.mal: defined using the language itself
+. <- rep("(def! not (fn* (a) (if a false true)))")
+. <- rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))")
+
+
+repeat {
+    line <- readline("user> ")
+    if (is.null(line)) { cat("\n"); break }
+    tryCatch({
+        cat(rep(line),"\n", sep="")
+    }, error=function(err) {
+        cat("Error: ", get_error(err),"\n", sep="")
+    })
+    # R debug/fatal with tracebacks:
+    #cat(rep(line),"\n", sep="")
+}