This image from a facebook posting emphasized the importance of both Steve Jobs and Dennis Ritchie.
Saturday, July 7, 2012
Two giants of computing who died in the same month!
This image from a facebook posting emphasized the importance of both Steve Jobs and Dennis Ritchie.
Wednesday, February 1, 2012
Python, finding nearest matching color name for RGB values
There are 147 standard color names for use in HTML. here is a simple Python code to find the nearest matching color name given input R,G, B values (from 0-255). The minimization criterion is the sum of absolute vaues of the differences from the color r, g, b values of the colornames.
"""
File colornames.py
Author Ernesto P. Adorio, Ph.D
Version 0.0.1 February 1, 2012
"""
# Src: http://www.w3schools.com/html/html_colornames.asp
lines = """AliceBlue #F0F8FF Shades Mix
AntiqueWhite #FAEBD7 Shades Mix
Aqua #00FFFF Shades Mix
Aquamarine #7FFFD4 Shades Mix
Azure #F0FFFF Shades Mix
Beige #F5F5DC Shades Mix
Bisque #FFE4C4 Shades Mix
Black #000000 Shades Mix
BlanchedAlmond #FFEBCD Shades Mix
Blue #0000FF Shades Mix
BlueViolet #8A2BE2 Shades Mix
Brown #A52A2A Shades Mix
BurlyWood #DEB887 Shades Mix
CadetBlue #5F9EA0 Shades Mix
Chartreuse #7FFF00 Shades Mix
Chocolate #D2691E Shades Mix
Coral #FF7F50 Shades Mix
CornflowerBlue #6495ED Shades Mix
Cornsilk #FFF8DC Shades Mix
Crimson #DC143C Shades Mix
Cyan #00FFFF Shades Mix
DarkBlue #00008B Shades Mix
DarkCyan #008B8B Shades Mix
DarkGoldenRod #B8860B Shades Mix
DarkGray #A9A9A9 Shades Mix
DarkGrey #A9A9A9 Shades Mix
DarkGreen #006400 Shades Mix
DarkKhaki #BDB76B Shades Mix
DarkMagenta #8B008B Shades Mix
DarkOliveGreen #556B2F Shades Mix
Darkorange #FF8C00 Shades Mix
DarkOrchid #9932CC Shades Mix
DarkRed #8B0000 Shades Mix
DarkSalmon #E9967A Shades Mix
DarkSeaGreen #8FBC8F Shades Mix
DarkSlateBlue #483D8B Shades Mix
DarkSlateGray #2F4F4F Shades Mix
DarkSlateGrey #2F4F4F Shades Mix
DarkTurquoise #00CED1 Shades Mix
DarkViolet #9400D3 Shades Mix
DeepPink #FF1493 Shades Mix
DeepSkyBlue #00BFFF Shades Mix
DimGray #696969 Shades Mix
DimGrey #696969 Shades Mix
DodgerBlue #1E90FF Shades Mix
FireBrick #B22222 Shades Mix
FloralWhite #FFFAF0 Shades Mix
ForestGreen #228B22 Shades Mix
Fuchsia #FF00FF Shades Mix
Gainsboro #DCDCDC Shades Mix
GhostWhite #F8F8FF Shades Mix
Gold #FFD700 Shades Mix
GoldenRod #DAA520 Shades Mix
Gray #808080 Shades Mix
Grey #808080 Shades Mix
Green #008000 Shades Mix
GreenYellow #ADFF2F Shades Mix
HoneyDew #F0FFF0 Shades Mix
HotPink #FF69B4 Shades Mix
IndianRed #CD5C5C Shades Mix
Indigo #4B0082 Shades Mix
Ivory #FFFFF0 Shades Mix
Khaki #F0E68C Shades Mix
Lavender #E6E6FA Shades Mix
LavenderBlush #FFF0F5 Shades Mix
LawnGreen #7CFC00 Shades Mix
LemonChiffon #FFFACD Shades Mix
LightBlue #ADD8E6 Shades Mix
LightCoral #F08080 Shades Mix
LightCyan #E0FFFF Shades Mix
LightGoldenRodYellow #FAFAD2 Shades Mix
LightGray #D3D3D3 Shades Mix
LightGrey #D3D3D3 Shades Mix
LightGreen #90EE90 Shades Mix
LightPink #FFB6C1 Shades Mix
LightSalmon #FFA07A Shades Mix
LightSeaGreen #20B2AA Shades Mix
LightSkyBlue #87CEFA Shades Mix
LightSlateGray #778899 Shades Mix
LightSlateGrey #778899 Shades Mix
LightSteelBlue #B0C4DE Shades Mix
LightYellow #FFFFE0 Shades Mix
Lime #00FF00 Shades Mix
LimeGreen #32CD32 Shades Mix
Linen #FAF0E6 Shades Mix
Magenta #FF00FF Shades Mix
Maroon #800000 Shades Mix
MediumAquaMarine #66CDAA Shades Mix
MediumBlue #0000CD Shades Mix
MediumOrchid #BA55D3 Shades Mix
MediumPurple #9370D8 Shades Mix
MediumSeaGreen #3CB371 Shades Mix
MediumSlateBlue #7B68EE Shades Mix
MediumSpringGreen #00FA9A Shades Mix
MediumTurquoise #48D1CC Shades Mix
MediumVioletRed #C71585 Shades Mix
MidnightBlue #191970 Shades Mix
MintCream #F5FFFA Shades Mix
MistyRose #FFE4E1 Shades Mix
Moccasin #FFE4B5 Shades Mix
NavajoWhite #FFDEAD Shades Mix
Navy #000080 Shades Mix
OldLace #FDF5E6 Shades Mix
Olive #808000 Shades Mix
OliveDrab #6B8E23 Shades Mix
Orange #FFA500 Shades Mix
OrangeRed #FF4500 Shades Mix
Orchid #DA70D6 Shades Mix
PaleGoldenRod #EEE8AA Shades Mix
PaleGreen #98FB98 Shades Mix
PaleTurquoise #AFEEEE Shades Mix
PaleVioletRed #D87093 Shades Mix
PapayaWhip #FFEFD5 Shades Mix
PeachPuff #FFDAB9 Shades Mix
Peru #CD853F Shades Mix
Pink #FFC0CB Shades Mix
Plum #DDA0DD Shades Mix
PowderBlue #B0E0E6 Shades Mix
Purple #800080 Shades Mix
Red #FF0000 Shades Mix
RosyBrown #BC8F8F Shades Mix
RoyalBlue #4169E1 Shades Mix
SaddleBrown #8B4513 Shades Mix
Salmon #FA8072 Shades Mix
SandyBrown #F4A460 Shades Mix
SeaGreen #2E8B57 Shades Mix
SeaShell #FFF5EE Shades Mix
Sienna #A0522D Shades Mix
Silver #C0C0C0 Shades Mix
SkyBlue #87CEEB Shades Mix
SlateBlue #6A5ACD Shades Mix
SlateGray #708090 Shades Mix
SlateGrey #708090 Shades Mix
Snow #FFFAFA Shades Mix
SpringGreen #00FF7F Shades Mix
SteelBlue #4682B4 Shades Mix
Tan #D2B48C Shades Mix
Teal #008080 Shades Mix
Thistle #D8BFD8 Shades Mix
Tomato #FF6347 Shades Mix
Turquoise #40E0D0 Shades Mix
Violet #EE82EE Shades Mix
Wheat #F5DEB3 Shades Mix
White #FFFFFF Shades Mix
WhiteSmoke #F5F5F5 Shades Mix
Yellow #FFFF00 Shades Mix
YellowGreen #9ACD32"""
def rgbfromstr(s):
# s starts with a #.
r, g, b = int(s[1:3],16), int(s[3:5], 16),int(s[5:7], 16)
return r, g, b
def findnearestcolorname(R,G, B, colorD):
mindiff = None
for d in colorD:
r, g, b = rgbfromstr(colorD[d])
diff = abs(R -r)*256 + abs(G-g)* 256 + abs(B- b)* 256
if mindiff is None or diff < mindiff:
mindiff = diff
mincolorname = d
return mincolorname
if __name__ == "__main__":
D={}
for line in lines.split("\n"):
tokens = line.split()
if len(tokens) > 1:
D[tokens[0]]= tokens[1]
R, G, B = 0, 127, 127
colorname = findnearestcolorname(0, 127, 127, D)
print hex(R), hex(G), hex(B)
print colorname, D[colorname]
When the above program runs, it outputs
$ python colornames.py
0x0 0x7f 0x7f
Teal #008080
Questions.
1. Modify the minimizaiton criterion to use least sum of squares of the differences.
2. Provide error checking for input R, G, B values to be within the interval [0, 255].
3. Procide different ways to specify the input RGB values, aside from the (R, G, B) values as done in the program above.
Wednesday, January 25, 2012
Simple floating point arithmetic for simple-forth
Here is our latest incarnation of simple-forth, a forth interpreter written in C.
This time we add floating point arithmetic capabilities. There are two basic ways to incorporate floating point capabilities. One is using the same integer stack and the other is using a separate foating point stack.
We use a separate floating point stack with maximum 32 elements. in our newest version shown below for simplicity. The built-in integer stack is 32 bits wide. Floating point numbers in our interpreter are 64 bit wide. The current stack element index is indicated by FP. The basic floating point operations are f+, f-, f*, f/ these Forth words are the equivalent floating point words corresponding to the built-in basic + - * / operator words
:
Here is compilation and a simple execution run.
Dont forget: a floating point number has a comma or an exponent in our simple-forth implementation.
This time we add floating point arithmetic capabilities. There are two basic ways to incorporate floating point capabilities. One is using the same integer stack and the other is using a separate foating point stack.
We use a separate floating point stack with maximum 32 elements. in our newest version shown below for simplicity. The built-in integer stack is 32 bits wide. Floating point numbers in our interpreter are 64 bit wide. The current stack element index is indicated by FP. The basic floating point operations are f+, f-, f*, f/ these Forth words are the equivalent floating point words corresponding to the built-in basic + - * / operator words
:
/*
file simple-forth-0.0.3.c
author Dr. Ernesto P. Adorio
UPDEPP (University of the Philippines,
Extension Program in Pampanga
Clarkfield, Pampanga
email ernesto.adorio@gmail.com
version 0.0.1 January 14, 2012 basic interpreter.
0.0.2 January 16, 2012 interactivity added.
0.0.3 January 25, 2012 basic floating point.
*/
#include
#include
#include
#include
enum {E_STACKUNDERFLOW, E_FSTACKUNDERFLOW} ERRCODES;
enum {L_EMIT, L_DOT,L_DOTT, L_SPACE, L_ADD, L_SUB, L_MUL, L_DIV, L_DROP, L_INT32, L_CR,
L_FNUM, L_FPLUS, L_FSUB, L_FMUL, L_FDIV, L_FDOT, L_FDOTT, L_FDROP,
L_BYE, L_EOS,L_ERROR} OPCODES;
const char *stdwords[] = { "emit", ".", ".t", "space", "+", "-", "*", "/", "drop", "int32", "cr",
"fnum", "f+", "f-", "f*" ,"f/", "f.","f.t","fdrop",
"bye",
"\n",
};
// "int32" and "fnum" are dummies.
#define MAXSTKLEN 32
#define MAXFSTKLEN 32
#define MAXTOKENLEN 128
int LENSTDWORDS = sizeof(stdwords)/sizeof(stdwords[0]);
char LINEBUFFER[256];
char *goodbye= "bye";
int ERRCODE = 0;
int SP = -1; /* stack pointer index */
int stack[MAXSTKLEN];
int opcode;
char *tokstart;
char *tokend;
int FP = -1; /* floating point stack index */
double fstack[MAXFSTKLEN];
int numbertype(char *s)
{
/*
Returns
0 - not a number!
1 - an integer
2 - a floating point number
*/
char *t = s;
while (isspace(*t)) t++;
if (*t == '\0') return 0;
if (*t == '+' || *t == '-') t++;
if (*t == '\0') return 0;
while (isdigit(*t)) t++;
if (*t == '\0') {
return 1; // an integer!
}
if (*t == '.') t++;
while (isdigit(*t)) t++;
if (*t == '\0') return 2;
if (*t == 'e') t++;
if (*t == '\0') return 0; // error!
if (*t == '+' || *t == '-') t++;
if (*t == '\0') return 0; // error!
while (isdigit(*t)) t++;
if (*t == '\0') return 2; // a floating point number!
return 0; // not an integer or floating point.
}
int eval(int opcode)
{
/* Evaluate opcode */
switch (opcode){
case L_EMIT:
//@@printf("opcode L_EMIT %s %d\n", tokstart, SP);
if (SP < 0) {
ERRCODE = E_STACKUNDERFLOW;
} else {
printf ("%c", stack[SP--]);
}
break;
case L_DOT:
printf("opcode L_EMIT %s %d\n", tokstart, SP);
if (SP < 0) {
ERRCODE = E_STACKUNDERFLOW;
printf("%s", "underflow!");
} else {
printf ("%d", stack[SP--]);
}
break;
case L_DOTT:
//@@printf("opcode L_EMIT %s %d\n", tokstart, SP);
if (SP < 0) {
ERRCODE = E_STACKUNDERFLOW;
printf("%s", "underflow!");
} else {
printf ("%d", stack[SP]);
}
break;
case L_SPACE:
printf ("%c", 32);
break;
case L_ADD:
//printf("opcode L_ADD %s\n", tokstart);
if (SP <= 0) {
ERRCODE = E_STACKUNDERFLOW;
printf("%s", "underflow!");
break;
}
stack[SP-1] += stack[SP];
SP--;
break;
case L_SUB:
//printf("opcode L_SUB %s\n", tokstart);
if (SP <= 0) {
ERRCODE = E_STACKUNDERFLOW;
printf("%s", "underflow!");
break;
}
stack[SP-1] -= stack[SP];
SP--;
break;
case L_MUL:
//printf("opcode L_MUL %s\n", tokstart);
if (SP <= 0) {
ERRCODE = E_STACKUNDERFLOW;
printf("%s", "underflow!");
break;
}
stack[SP-1] *= stack[SP];
SP--;
break;
case L_DIV:
//printf("opcode L_DIV %s\n", tokstart);
if (SP <= 0) {
ERRCODE = E_STACKUNDERFLOW;
printf("%s", "underflow!");
break;
}
stack[SP-1] /= stack[SP];
SP--;
break;
case L_INT32:
//printf("opcode L_INT32 %s\n",tokstart);
stack[++SP]= atoi(tokstart);
// printf("@@@ pushing an integer!");
break;
case L_DROP:
//printf("opcode L_DROP %s \n", tokstart);
SP=SP -1;
break;
case L_CR:
// printf("opcode L_CR %s \n", tokstart);
printf("\n");
break;
/* simple floating point features */
case L_FNUM:
//printf("floating point number %s\n",tokstart);
fstack[++FP]= atof(tokstart);
break;
case L_FPLUS:
if (FP <= 0) {
ERRCODE = E_FSTACKUNDERFLOW;
printf("%s", "fstack underflow!");
break;
}
fstack[FP-1] += fstack[FP];
FP--;
break;
case L_FSUB:
if (FP <= 0) {
ERRCODE = E_FSTACKUNDERFLOW;
printf("%s", "fstack underflow!");
break;
}
fstack[FP-1] -= fstack[FP];
FP--;
break;
case L_FMUL:
if (FP <= 0) {
ERRCODE = E_FSTACKUNDERFLOW;
printf("%s", "fstack underflow!");
break;
}
fstack[FP-1] *= fstack[FP];
FP--;
break;
case L_FDIV:
if (FP <= 0) {
ERRCODE = E_FSTACKUNDERFLOW;
printf("%s", "fstack underflow!");
break;
}
fstack[FP-1] /= fstack[FP];
FP--;
break;
case L_FDOT:
printf("opcode FDOT %s\n", tokstart);
if (FP < 0) {
ERRCODE = E_FSTACKUNDERFLOW;
printf("%s", "underflow!");
} else {
printf ("%f", fstack[FP--]);
}
break;
case L_FDOTT:
//@@printf("opcode L_EMIT %s %d\n", tokstart, SP);
if (SP < 0) {
ERRCODE = E_FSTACKUNDERFLOW;
printf("%s", "underflow!");
} else {
printf ("%f", fstack[FP]);
}
break;
case L_BYE:
printf("Terminating... ");
break;
default:
;
break;
}
}
void nexttoken()
{
tokstart = tokend;
//@ printf("inside nexttoken [%s]", tokstart);
/* ignore leading white spaces */
while (isspace(*tokstart)) tokstart++;
/* find terminating space of end of string */
tokend = tokstart;
while (!isspace(*tokend) && *tokend != '\0') tokend++;
/* string terminator */
if (*tokend != '\0') {
*tokend = '\0';
tokend ++;
}
/* get opcode */
opcode = -1;
if (tokend == tokstart) {
opcode = L_EOS;
return;
}
//@@@ printf("token [%s]\n", tokstart);
for (int i =0; i < LENSTDWORDS; i++) {
if (strcmp(stdwords[i], tokstart) == 0){
opcode = i;
break;
}
}
if (opcode != -1) {
return;
}
int ntype = numbertype(tokstart);
if (ntype == 1){
/* is this a number ?*/
opcode = L_INT32;
} else if (ntype == 2) {
opcode = L_FNUM;
} else if (opcode == -1){
opcode = L_ERROR;
};
}
int main(){
while (1) {
printf("> ");
if (fgets(LINEBUFFER, 250, stdin)!= NULL) {
tokend=LINEBUFFER;
} else {
tokend= goodbye;
}
while (1) {
nexttoken();
eval(opcode);
if (opcode == L_BYE) {
return 0;
}
if (opcode ==L_EOS) {
break;
}
if (ERRCODE != 0) {
printf("ERRORCODE [%d]", ERRCODE);
break;
};
}
}
printf("\n");
return 0;
}
Here is compilation and a simple execution run.
gcc simple-forth-0.0.3.c -g -std=c99 -o simple-forth toto@toto-Aspire-4520:~/Blogs/my-other-life-as-programmer/forth$ ./simple-forth > 23.34 -56.12 f* f. -1309.840800> bye Terminating...
Dont forget: a floating point number has a comma or an exponent in our simple-forth implementation.
Tuesday, January 24, 2012
Terminal interactivity added to simple-forth.
Our previous Forth interpreter processed only fixed strings. To add interactivity from a console or terminal, we have to read an input string to a buffer. There is more than one way, we may use scanf. Another one, much better is fgets which avoids buffer overruns. Here is our version 0.0.2 with terminal interactivity.
Save file to simple-forth-0.0.2.c, then compile it using the following command:
: gcc simple-forth.c -std=c99 -o simple-forth-0.0.2
Then run it by issuing ./simple-forth00.0.2 Here is an uninspired terminal run:
Next, we will add add a floating point computation capabilities using a separate stack.
/*
file simple-forth-0.0.2.c
author Dr. Ernesto P. Adorio
UPDEPP (University of the Philippines,
Extension Program in Pampanga
Clarkfield, Pampanga
email ernesto.adorio@gmail.com
version 0.0.1 January 14, 2012 basic interpreter.
0.0.2 January 16, 2012 interactivity added.
*/
#include
#include
#include
#include
enum {E_STACKUNDERFLOW} ERRCODES;
enum {L_EMIT, L_DOT,L_DOTT, L_SPACE, L_ADD, L_SUB, L_MUL, L_DIV, L_DROP, L_INT32, L_CR, L_BYE, L_EOS,L_ERROR} OPCODES;
const char *stdwords[] = {
"emit",
".",
".t",
"space",
"+",
"-",
"*",
"/",
"drop",
"int32",
"cr",
"bye",
"\n",
};
#define MAXSTKLEN 32
#define MAXFSTKLEN 32
#define MAXTOKENLEN 128
int LENSTDWORDS = sizeof(stdwords)/sizeof(stdwords[0]);
char LINEBUFFER[256];
char *goodbye= "bye";
int ERRCODE = 0;
int SP = -1; /* stack pointer index */
int stack[MAXSTKLEN];
double fstack[MAXFSTKLEN];
int opcode;
char *tokstart;
char *tokend;
int eval(int opcode)
{
/* Evaluate opcode */
switch (opcode){
case L_EMIT:
//@@printf("opcode L_EMIT %s %d\n", tokstart, SP);
if (SP < 0) {
ERRCODE = E_STACKUNDERFLOW;
} else {
printf ("%c", stack[SP--]);
}
break;
case L_DOT:
//@@printf("opcode L_EMIT %s %d\n", tokstart, SP);
if (SP < 0) {
ERRCODE = E_STACKUNDERFLOW;
printf("%s", "underflow!");
} else {
printf ("%d", stack[SP--]);
}
break;
case L_DOTT:
//@@printf("opcode L_EMIT %s %d\n", tokstart, SP);
if (SP < 0) {
ERRCODE = E_STACKUNDERFLOW;
printf("%s", "underflow!");
} else {
printf ("%d", stack[SP]);
}
break;
case L_SPACE:
printf ("%c", 32);
break;
case L_ADD:
//printf("opcode L_ADD %s\n", tokstart);
if (SP <= 0) {
ERRCODE = E_STACKUNDERFLOW;
printf("%s", "underflow!");
break;
}
stack[SP-1] += stack[SP];
SP--;
break;
case L_SUB:
//printf("opcode L_SUB %s\n", tokstart);
if (SP <= 0) {
ERRCODE = E_STACKUNDERFLOW;
printf("%s", "underflow!");
break;
}
stack[SP-1] -= stack[SP];
SP--;
break;
case L_MUL:
//printf("opcode L_MUL %s\n", tokstart);
if (SP <= 0) {
ERRCODE = E_STACKUNDERFLOW;
printf("%s", "underflow!");
break;
}
stack[SP-1] *= stack[SP];
SP--;
break;
case L_DIV:
//printf("opcode L_DIV %s\n", tokstart);
if (SP <= 0) {
ERRCODE = E_STACKUNDERFLOW;
printf("%s", "underflow!");
break;
}
stack[SP-1] /= stack[SP];
SP--;
break;
case L_INT32:
//printf("opcode L_INT32 %s\n",tokstart);
stack[++SP]= atoi(tokstart);
break;
case L_DROP:
//printf("opcode L_DROP %s \n", tokstart);
SP=SP -1;
break;
case L_CR:
// printf("opcode L_CR %s \n", tokstart);
printf("\n");
break;
default:
;
break;
}
}
void nexttoken()
{
tokstart = tokend;
//@ printf("inside nexttoken [%s]", tokstart);
/* ignore leading white spaces */
while (isspace(*tokstart)) tokstart++;
/* find terminating space of end of string */
tokend = tokstart;
while (!isspace(*tokend) && *tokend != '\0') tokend++;
/* string terminator */
if (*tokend != '\0') {
*tokend = '\0';
tokend ++;
}
/* get opcode */
opcode = -1;
if (tokend == tokstart) {
opcode = L_EOS;
return;
}
/*@@@ printf("token [%s]\n", tokstart); */
for (int i =0; i < LENSTDWORDS; i++) {
if (strcmp(stdwords[i], tokstart) == 0){
opcode = i;
//@ printf("opcde [%d]", opcode);
break;
}
}
if (opcode == -1){
opcode = L_INT32;
}
}
int main(){
while (1) {
// read string.
printf("> ");
if (fgets(LINEBUFFER, 250, stdin)!= NULL) {
tokend=LINEBUFFER;
// @@@ printf("input string [%s]", LINEBUFFER);
} else {
tokend= goodbye;
}
// eval
// printf ("Entering evaluation loop.\n");
while (1) {
nexttoken();
//@ printf ("[%d] %s", opcode, tokstart);
eval(opcode);
if (opcode== L_BYE) {
//printf ("%% opcode is L_BYE");
return 0;
}
if (opcode ==L_EOS) {
break;
}
if (ERRCODE != 0) {
printf("ERRORCODE [%d]", ERRCODE);
break;
};
}
// loop back unless BYE!
}
printf("\n");
return 0;
}
Save file to simple-forth-0.0.2.c, then compile it using the following command:
: gcc simple-forth.c -std=c99 -o simple-forth-0.0.2
Then run it by issuing ./simple-forth00.0.2 Here is an uninspired terminal run:
> 2 3 - 1 + . 0> 56 emit 8> 97 emit a> 64 emit @> > > bye
Next, we will add add a floating point computation capabilities using a separate stack.
Tuesday, January 17, 2012
Tiobe rankings of programming languages
Click on for the latest popularity rankings of programming languages. It is not based on absolute value but on the relative change of market share.
For January 2012, Objective C showed the fastest growth. Click on the link for the the definition of the Tiobe index.
The next popular is C# followed by C and Javascript. On the other hand, based on absolute market share, the top languages are Java, C, C#, C++, Objective-C, PHP and Visual Basic. Our favorite language Python is at #8. Interesting to note that the statistical software R is at #19.
For January 2012, Objective C showed the fastest growth. Click on the link for the the definition of the Tiobe index.
The next popular is C# followed by C and Javascript. On the other hand, based on absolute market share, the top languages are Java, C, C#, C++, Objective-C, PHP and Visual Basic. Our favorite language Python is at #8. Interesting to note that the statistical software R is at #19.
Saturday, January 14, 2012
Does a number string represents an integer or a floating value in C?
I got the shock of my blogging life when I cannot access an old post about the evils of the C function atof. Here is a code which return 1 for integers and 2 for floating point and 0 if not a valid integer or a valid float.
Remove the deubgging printf statements when you use it for applications.
When the program is run, it returns a code of 2 to denote a floating point number, a 1 for an integer, and a 0 if not a number.
/*
author Ernesto P. Adorio
UPDEPP (University of the
Philippines, Extension Program
in Pampanga, Clarkfield, Pampanga
email ernesto. adorio@ gmail.com [remove spaces]
version 0.0.1 january 14, 2012
*/
#include
#include
int numbertype(char *s)
{
char *t = s;
while (isspace(*t)) t++;
if (*t == '\0') return 0;
// number sign
printf("ltrimmed [%s]", t);
if (*t == '+' || *t == '-') t++;
if (*t == '\0') return 0;
printf("after sign [%s]", t);
while (isdigit(*t)) t++;
printf("after digits [%s]", t);
if (*t == '\0') return 1; // an integer!
// floating point??
printf ("decimal point? [%s] ", t);
if (*t == '.') t++;
printf ("fractional digits?");
while (isdigit(*t)) t++;
if (*t == '\0') return 2;
// exponent part.
printf ("testing exponent part %s", t);
if (*t == 'e') t++;
printf ("after 'e' ");
if (*t == '\0') return 0; // error!
printf ("sign after e?", t);
if (*t == '+' || *t == '-') t++;
printf("%s", t);
if (*t == '\0') return 0; // error!
while (isdigit(*t)) t++;
if (*t == '\0') return 2; // a floating point number!
return 0; // not an integer or floating point.
}
int main()
{
printf("numtype =[%d]", numbertype("-123.34"));
};
Remove the deubgging printf statements when you use it for applications.
When the program is run, it returns a code of 2 to denote a floating point number, a 1 for an integer, and a 0 if not a number.
A basic Forth language interpreter (non-interactive)
Last time we showed a simple tokenizer for a Forth interpreter. We find it easier to combine the ideas in that post to create a simple Forth engine which process a simple string.
We will expound further on this until we successfully build a compiler for a non-standard Forth language.
Have fun working on this. The current version works on simple strings but specified on the source code itself. We will introduce interactivity and expand the capabilities of this simple Forth interpreter.
We will expound further on this until we successfully build a compiler for a non-standard Forth language.
Have fun working on this. The current version works on simple strings but specified on the source code itself. We will introduce interactivity and expand the capabilities of this simple Forth interpreter.
/*
file simple-forth.c
author Dr. Ernesto P. Adorio
UPDEPP (University of the Philippines,
Extension Program in Pampanga
Clarkfield, Pampanga
email ernesto.adorio@gmail.com
version 0.0.1 January 14, 2012
*/
#include
#include
#include
#include
#define MAXSTKLEN 32
#define MAXTOKENLEN 128
enum {L_EMIT, L_ADD, L_SUB, L_MUL, L_DIV, L_POP, L_INT32, L_CR, L_ERROR} OPCODES;
const char *stdwords[] = {
".",
"+",
"-",
"*",
"/",
"pop",
"int32",
"cr",
};
int LENSTDWORDS = 8;
int stack[MAXSTKLEN];
int SP = 0; /* stack pointer index */
int main(){
char tokens[] = " 123 34 + . cr 567 -3456 * . cr";
char *tokstart = tokens;
char *tokend = tokstart;
int opcode;
/* @@@ printf("tokstart: %s\n", tokstart);*/
tokend = tokens;
while (1) {
tokstart = tokend;
/* ignore leading white spaces */
while (isspace(*tokstart)) tokstart++;
/* find terminating space of end of string */
tokend = tokstart;
while (!isspace(*tokend) && *tokend != '\0') tokend++;
/* string terminator */
if (*tokend != '\0') {
*tokend = '\0';
tokend ++;
} else {
break;
}
/* get opcode */
opcode = -1;
/*@@@ printf("token [%s]\n", tokstart); */
for (int i =0; i < LENSTDWORDS; i++) {
if (strcmp(stdwords[i], tokstart) == 0){
opcode = i;
break;
}
}
if (opcode == -1){
opcode = L_INT32;
}
/* Evaluate opcode */
switch (opcode){
case L_EMIT:
//printf("opcode L_EMIT %s \n", tokstart);
printf ("%d", stack[SP--] );
break;
case L_ADD:
//printf("opcode L_ADD %s\n", tokstart);
stack[SP-1] += stack[SP];
SP--;
break;
case L_SUB:
//printf("opcode L_SUB %s\n", tokstart);
stack[SP-1] += stack[SP];
SP--;
break;
case L_MUL:
//printf("opcode L_MUL %s\n", tokstart);
stack[SP-1] *= stack[SP];
SP--;
break;
case L_DIV:
//printf("opcode L_DIV %s\n", tokstart);
stack[SP-1] /= stack[SP];
SP--;
break;
case L_INT32:
//printf("opcode L_INT32 %s\n",tokstart);
stack[++SP]= atoi(tokstart);
break;
case L_POP:
//printf("opcode L_POP %s \n", tokstart);
SP--;
break;
case L_CR:
// printf("opcode L_CR %s \n", tokstart);
printf("\n");
}
}
printf("\n");
return 0;
}
Save the code to a file simple-forth.c, then compile using the following command line on the directory where the source file is stored.
gcc simple-forth.c -std=c99 -o forth
It should compile cleanly, then execute the executible by issuing ./forth
When the program runs, it prints out
toto@toto-Aspire-4520:~/Blogs/my-other-life-as-programmer/forth$ ./forth 157 -1959552
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