From df866558a4aa2164bc9f3fce6f1aeab42cfead5f Mon Sep 17 00:00:00 2001
From: John Kerl <kerl.john.r@gmail.com>
Date: Tue, 5 May 2015 22:11:18 -0700
Subject: [PATCH] debug

---
 c/todo.txt            | 13 +++++++
 c/tools/gen-squares.c | 87 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 100 insertions(+)
 create mode 100755 c/tools/gen-squares.c

diff --git a/c/todo.txt b/c/todo.txt
index 0872e24df..34badd9c7 100644
--- a/c/todo.txt
+++ b/c/todo.txt
@@ -1,3 +1,16 @@
+================================================================
+!! BUGFIX !!
+
+$ echo 'x=0' | mlr put '$y=-2*$x+3'
+x=0,y=-3.000000
+
+$ echo 'x=0' | mlr put '$y=(-2*$x)+3'
+x=0,y=3.000000
+
+$ echo 'x=0' | mlr put '$y=-(2*$x)+3'
+x=0,y=-3.000000
+
+
 ================================================================
 NEATEN
 
diff --git a/c/tools/gen-squares.c b/c/tools/gen-squares.c
new file mode 100755
index 000000000..38eba8a3f
--- /dev/null
+++ b/c/tools/gen-squares.c
@@ -0,0 +1,87 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <unistd.h>
+
+// Samples unit-uniform x,y pairs, conditioned on being in two subboxes the size
+// of which is described by the "chomp" parameter.
+//
+// 0 < chomp < 1:
+//
+// +----------------oooooooo
+// |                oooooooo
+// |                oooooooo
+// |                oooooooo <-- chomp
+// |                       |
+// |                       |
+// oooooooo                | <-- 1-chomp
+// oooooooo                |
+// oooooooo                |
+// oooooooo----------------+
+//        ^        ^
+//        |        |
+//    1-chomp    chomp
+//
+// chomp = 0 means output all x,y pairs
+//
+// -1 < chomp < 0:
+//    1+chomp    -chomp
+//        |        |
+//        v        v
+// oooooooo----------------+
+// oooooooo                |
+// oooooooo                |
+// oooooooo                | <-- -chomp
+// |                       |
+// |                       |
+// |                oooooooo <-- 1+chomp
+// |                oooooooo
+// |                oooooooo
+// +----------------oooooooo
+
+static void usage(char* argv0) {
+	fprintf(stderr, "Usage: %s [chomp [n]]\n", argv0);
+	exit(1);
+}
+
+int main(int argc, char** argv) {
+	double chomp = 0.5;
+	int n = 100000;
+	if (argc == 2) {
+		if (sscanf(argv[1], "%lf", &chomp) != 1)
+			usage(argv[0]);
+	} else if (argc == 3) {
+		if (sscanf(argv[1], "%lf", &chomp) != 1)
+			usage(argv[0]);
+		if (sscanf(argv[2], "%d", &n) != 1)
+			usage(argv[0]);
+	} else {
+		usage(argv[0]);
+	}
+
+	srand(time(0) ^ getpid());
+	if (chomp > 0.0) {
+		double lo = 1.0 - chomp;
+		double hi = chomp;
+		for (int i = 0; i < n; /* increment in loop */) {
+			double x = (double)rand() / (double)RAND_MAX;
+			double y = (double)rand() / (double)RAND_MAX;
+			if ((x < lo && y < lo) || (x > hi && y > hi)) {
+				i++;
+				printf("x=%.18lf,y=%.18lf\n", x, y);
+			}
+		}
+	} else {
+		double lo = 1+chomp;
+		double hi = -chomp;
+		for (int i = 0; i < n; /* increment in loop */) {
+			double x = (double)rand() / (double)RAND_MAX;
+			double y = (double)rand() / (double)RAND_MAX;
+			if ((x < lo && y > hi) || (x > hi && y < lo)) {
+				i++;
+				printf("x=%.18lf,y=%.18lf\n", x, y);
+			}
+		}
+	}
+	return 0;
+}