From f34d9a4160b45eebda8f727e3d75946e88abe3f5 Mon Sep 17 00:00:00 2001
From: June McEnroe <june@causal.agency>
Date: Mon, 3 Oct 2016 23:46:20 -0400
Subject: What am I even doing?

It's Monday night and I've had a lot to drink because I didn't like what
Monday day was like. Ain't that just the way?
---
 .bin/rpn.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 install.sh |  1 +
 2 files changed, 98 insertions(+)
 create mode 100755 .bin/rpn.c

diff --git a/.bin/rpn.c b/.bin/rpn.c
new file mode 100755
index 00000000..c2dc4ccf
--- /dev/null
+++ b/.bin/rpn.c
@@ -0,0 +1,97 @@
+#if 0
+exec cc -Wall -Wextra $@ -ledit -o $(dirname $0)/rpn $0
+#endif
+
+#include <assert.h>
+#include <ctype.h>
+#include <err.h>
+#include <histedit.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sysexits.h>
+
+static struct {
+    int64_t data[1024];
+    size_t len;
+    int radix;
+} stack = { .radix = 10 };
+
+static void push(int64_t val) {
+    stack.data[stack.len++] = val;
+    assert(stack.len < sizeof(stack.data));
+}
+
+static int64_t pop(void) {
+    if (stack.len == 0) return 0;
+    return stack.data[--stack.len];
+}
+
+static bool stack_op(char op) {
+    int64_t a, b;
+    switch (op) {
+        case '$': pop();
+        break; case '\\': a = pop(); b = pop(); push(a); push(b);
+        break; case ':': a = pop(); push(a); push(a);
+        break; case '_': a = pop(); push(-a);
+        break; case '+': a = pop(); push(pop() + a);
+        break; case '-': a = pop(); push(pop() - a);
+        break; case '*': a = pop(); push(pop() * a);
+        break; case '/': a = pop(); push(pop() / a);
+        break; case '%': a = pop(); push(pop() % a);
+        break; case '~': a = pop(); push(~a);
+        break; case '&': a = pop(); push(pop() & a);
+        break; case '|': a = pop(); push(pop() | a);
+        break; case '^': a = pop(); push(pop() ^ a);
+        break; case '<': a = pop(); push(pop() << a);
+        break; case '>': a = pop(); push(pop() >> a);
+        break; case '.': a = pop(); printf("%lld\n", a);
+        break; case ',': a = pop(); printf("%c\n", (char) a);
+        break; default: return false;
+    }
+    return true;
+}
+
+static char *prompt(EditLine *el __attribute((unused))) {
+    static char p[4096];
+    if (stack.len == 0) return "[] ";
+
+    size_t q = 0;
+    for (size_t i = 0; i < stack.len; ++i) {
+        q += (size_t) snprintf(&p[q], sizeof(p) - 3 - q, " %lld", stack.data[i]);
+    }
+    p[0] = '[';
+    p[q] = ']';
+    p[++q] = ' ';
+    p[++q] = 0;
+
+    return p;
+}
+
+int main(int argc __attribute((unused)), char *argv[]) {
+    EditLine *el = el_init(argv[0], stdin, stdout, stderr);
+    el_set(el, EL_PROMPT, prompt);
+
+    for (;;) {
+        int count;
+        const char *line = el_gets(el, &count);
+        if (count < 0) err(EX_IOERR, "el_gets");
+        if (!line) break;
+
+        while (*line) {
+            char *rest;
+            int64_t val = strtoll(line, &rest, stack.radix);
+
+        while (*line) {
+            if (isdigit(*line))
+                push(strtoll(line, (char **) &line, 0)); // XXX: ???
+            else
+                stack_op(*line++);
+        }
+    }
+    putchar('\n');
+
+    el_end(el);
+    return EX_OK;
+}
diff --git a/install.sh b/install.sh
index fd3f7192..98b4de54 100755
--- a/install.sh
+++ b/install.sh
@@ -25,6 +25,7 @@ link .bin/manpager
 link .bin/pbcopy
 link .bin/pbd.c
 link .bin/pbpaste
+link .bin/rpn.c
 link .bin/xx.c
 link .config/git/config
 link .config/git/ignore
-- 
cgit 1.4.1