ref: 70de7329ed0cdf8dac3e7e9126f13e5ed61d2c28
parent: 9853749352c8acaf7ddb4e0c4fef457008a95bba
author: phil9 <telephil9@gmail.com>
date: Mon Dec 5 00:42:59 EST 2022
implement randomGaussian()
--- a/a.h
+++ b/a.h
@@ -30,6 +30,8 @@
int registerpixels(lua_State*);
void lpushpixels(lua_State*);
+double randomgaussian(double, double);
+
extern int drawing;
extern int looping;
extern int framerate;
--- a/api.c
+++ b/api.c
@@ -592,6 +592,31 @@
return 0;
}
+int
+crandomgaussian(lua_State *L)
+{+ double m, s, g;
+ int n;
+
+ m = 0.0;
+ s = 1.0;
+ n = lua_gettop(L);
+ switch(n){+ case 2:
+ s = luaL_checknumber(L, 2);
+ case 1:
+ m = luaL_checknumber(L, 1);
+ break;
+ case 0:
+ break;
+ default:
+ luaL_error(L, "invalid argument count");
+ }
+ g = randomgaussian(m, s);
+ lua_pushnumber(L, g);
+ return 1;
+}
+
void
registerfunc(lua_State *L, const char *name, int(*f)(lua_State*))
{@@ -641,5 +666,6 @@
registerfunc(L, "color", ccolor);
registerfunc(L, "loadPixels", cloadpixels);
registerfunc(L, "updatePixels", cupdatepixels);
+ registerfunc(L, "randomGaussian", crandomgaussian);
}
--- /dev/null
+++ b/math.c
@@ -1,0 +1,26 @@
+#include "a.h"
+
+double
+randomgaussian(double mean, double sd)
+{+ static int prev = 0;
+ static double y2;
+ double y1, x1, x2, w;
+
+ if(prev){+ y1 = y2;
+ prev = 0;
+ }else{+ do{+ x1 = 2*frand() - 1;
+ x2 = 2*frand() - 1;
+ w = x1 * x1 + x2 * x2;
+ }while(w >= 1);
+ w = sqrt(-2 * log(w) / w);
+ y1 = x1 * w;
+ y2 = x2 * w;
+ prev = 1;
+ }
+ return y1 * sd + mean;
+}
+
--- a/mkfile
+++ b/mkfile
@@ -4,7 +4,7 @@
TARG=slug
LIB=lua/liblua.a.$O
HFILES=a.h
-OFILES=slug.$O api.$O color.$O pixels.$O
+OFILES=slug.$O api.$O color.$O pixels.$O math.$O
MAN=/sys/man/1
</sys/src/cmd/mkone
--- /dev/null
+++ b/samples/gaussian.lua
@@ -1,0 +1,14 @@
+#!/bin/slug
+
+function setup()
+ size(400, 400)
+ background(200)
+ for y = 0, 399 do
+ x = math.floor(randomGaussian() * 60)
+ line(200, y, 200 + x, y)
+ end
+end
+
+function draw()
+end
+
--- a/slug.man
+++ b/slug.man
@@ -298,6 +298,16 @@
.TP
\f5mouseY
Global variable containing the vertical coordinate of the mouse.
+.SS Math
+.TP
+\f5randomGaussian()
+.PD 0
+.TP
+\f5randomGaussian(\f2mean\fP)
+.PD 0
+.TP
+\f5randomGaussian(\f2mean\fP, \f2stddev\fP)
+Returns a random number fitting a Gaussian (or normal) distribution. The arguments are the mean and the standard deviation which defaults to 0.0 and 1.0 respectively.
.SH AUTHOR
phil9