4 files changed, 99 insertions, 0 deletions
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..204d390
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/sorth
diff --git a/README b/README
new file mode 100644
index 0000000..cc4270e
--- /dev/null
+++ b/README
@@ -0,0 +1 @@
+bad forth in <100 lines of C
diff --git a/build.sh b/build.sh
new file mode 100755
index 0000000..f9c52b1
--- /dev/null
+++ b/build.sh
@@ -0,0 +1,2 @@
+#!/bin/sh
+gcc -o sorth sorth.c -g3 -O0
diff --git a/sorth.c b/sorth.c
new file mode 100644
index 0000000..82cfb3a
--- /dev/null
+++ b/sorth.c
@@ -0,0 +1,95 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+long stack[1024] = {0};
+size_t stack_ptr = 0;
+bool strict = false;
+
+static void panic(const char *msg) {
+	fprintf(stderr, "%s\n", msg);
+	exit(EXIT_FAILURE);
+}
+
+static bool is(const char *s1, const char *s2) {
+	return strcmp(s1, s2) == 0;
+}
+
+static long pop(void) {
+	if (stack_ptr == 0)
+		panic("stack undeflow");
+	return stack[--stack_ptr];
+}
+
+static void push(long v) {
+	if (stack_ptr >= sizeof(stack) / sizeof(stack[0]))
+		panic("stack overflow");
+	stack[stack_ptr++] = v;
+}
+
+#define OP(X) } else if (strcmp(s, X) == 0) {
+static void exec(const char *s) {
+	if (s[0] >= '0' && s[0] <= '9') {
+		push(atol(s));
+	OP("drop")
+		pop();
+	OP("dup")
+		const long a = pop();
+		push(a); push(a);
+	OP("swap")
+		const long a = pop();
+		const long b = pop();
+		push(a); push(b);
+	OP("over")
+		const long a = pop();
+		const long b = pop();
+		push(a); push(b); push(a);
+	OP("rot")
+		const long a = pop();
+		const long b = pop();
+		const long c = pop();
+		push(b); push(a); push(c);
+	OP("+")
+		push(pop() + pop());
+	OP("-")
+		const long a = pop();
+		push(pop() - a);
+	OP("*")
+		push(pop() * pop());
+	OP("/")
+		const long a = pop();
+		push(pop() / a);
+	OP("%")
+		const long a = pop();
+		push(pop() % a);
+	OP(".s")
+		printf("\x1b[94m<%zu> ", stack_ptr);
+		for (size_t i = 0; i < stack_ptr; i++)
+			printf("%ld ", stack[i]);
+		printf("\x1b[0m\n");
+	OP(".")
+		printf("\x1b[94m%ld\x1b[0m\n", pop());
+	} else {
+		fprintf(stderr, "unrecognized word '%s'\n", s);
+		if (strict)
+			exit(EXIT_FAILURE);
+	}
+}
+
+int main(int argc, char **argv) {
+	char line[1024] = {0};
+	const char *delim = " \t\n\v\r";
+
+	if (argc > 1 && argv[1][0] == '-' && strchr(argv[1], 's'))
+		strict = true;
+
+	while (fgets(line, sizeof(line) - 1, stdin)) {
+		char *tok = strtok(line, delim);
+		while (tok != NULL) {
+			exec(tok);
+			tok = strtok(NULL, delim);
+		}
+	}
+	return 0;
+}