1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
|
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)))
}
}
is_macro_call <- function(ast, env) {
if(.list_q(ast) &&
.symbol_q(ast[[1]]) &&
(!.nil_q(Env.find(env, ast[[1]])))) {
exp <- Env.get(env, ast[[1]])
return(.malfunc_q(exp) && exp$ismacro)
}
FALSE
}
macroexpand <- function(ast, env) {
while(is_macro_call(ast, env)) {
mac <- Env.get(env, ast[[1]])
ast <- fapply(mac, slice(ast, 2))
}
ast
}
eval_ast <- function(ast, env) {
if (.symbol_q(ast)) {
Env.get(env, ast)
} else if (.list_q(ast)) {
new.listl(lapply(ast, function(a) EVAL(a, env)))
} else if (.vector_q(ast)) {
new.vectorl(lapply(ast, function(a) EVAL(a, env)))
} else if (.hash_map_q(ast)) {
lst <- list()
for(k in ls(ast)) {
lst[[length(lst)+1]] = k
lst[[length(lst)+1]] = EVAL(ast[[k]], env)
}
new.hash_mapl(lst)
} else {
ast
}
}
EVAL <- function(ast, env) {
repeat {
#cat("EVAL: ", .pr_str(ast,TRUE), "\n", sep="")
if (!.list_q(ast)) {
return(eval_ast(ast, env))
}
# apply list
ast <- macroexpand(ast, env)
if (!.list_q(ast)) return(ast)
switch(paste("l",length(ast),sep=""),
l0={ return(ast) },
l1={ a0 <- ast[[1]]; a1 <- NULL; a2 <- NULL },
l2={ a0 <- ast[[1]]; a1 <- ast[[2]]; a2 <- NULL },
{ a0 <- ast[[1]]; a1 <- ast[[2]]; a2 <- ast[[3]] })
if (length(a0) > 1) a0sym <- "__<*fn*>__"
else a0sym <- as.character(a0)
if (a0sym == "def!") {
res <- EVAL(a2, env)
return(Env.set(env, a1, res))
} else if (a0sym == "let*") {
let_env <- new.Env(env)
for(i in seq(1,length(a1),2)) {
Env.set(let_env, a1[[i]], EVAL(a1[[i+1]], let_env))
}
ast <- a2
env <- let_env
} else if (a0sym == "quote") {
return(a1)
} else if (a0sym == "quasiquote") {
ast <- quasiquote(a1)
} else if (a0sym == "defmacro!") {
func <- EVAL(a2, env)
func$ismacro = TRUE
return(Env.set(env, a1, func))
} else if (a0sym == "macroexpand") {
return(macroexpand(a1, env))
} 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(nil)
ast <- ast[[4]]
} else {
ast <- a2
}
} else if (a0sym == "fn*") {
return(malfunc(EVAL, 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*", new.list())
# 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) \")\")))))")
. <- rep("(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))")
. <- rep("(defmacro! or (fn* (& xs) (if (empty? xs) nil (if (= 1 (count xs)) (first xs) `(let* (or_FIXME ~(first xs)) (if or_FIXME or_FIXME (or ~@(rest xs))))))))")
args <- commandArgs(trailingOnly = TRUE)
if (length(args) > 0) {
Env.set(repl_env, "*ARGV*", new.listl(slice(list(args),2)))
. <- rep(concat("(load-file \"", args[[1]], "\")"))
quit(save="no", status=0)
}
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="")
}
|
